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Chapter 7. GPS-Aided Integrated Navigation with GFINS

All inertial navigation systems, whether gimbaled INS, strap-down INS, or GFINS, have a common characteristic that position error accumulates with time, while a GPS navigation device does not. Therefore, the inertial navigation system may be naturally integrated with a GPS navigation device. It’s especially necessary for GFINS to integrate with GPS.

Hongjin Zhou, Yunhai Zhong, Hui Song, Su Wang

Chapter 5. Accelerometer Noise Characteristics Analysis and Denoising

Accelerometer outputs are the only information used for GFINS parameter resolution. The performance of accelerometers is critical to GFINS navigation parameter resolution accuracy; in particular, the output noise of the accelerometers directly affects attitude and position resolution accuracy. Accelerometer noise characteristics identification and denoising should be done before the use of accelerometer output.

Hongjin Zhou, Yunhai Zhong, Hui Song, Su Wang

Chapter 1. Introduction

An inertial navigation system (INS) is a type of navigation system that can function independently without any outside information. The traditional INS measure a vehicle’s linear motion and angular motion by gyroscopes and accelerometers, and then resolves the vehicle’s attitude and position. The primary inertial units of the INS include the gyroscope and accelerometer. The gyroscope is used to measure the vehicle’s angular motion, and the accelerometer is used to measure the vehicle’s linear motion. As the inertial navigation technology develops, researchers find that a vehicle’s angular motion can also be measured via lever-arm effect sensed by an accelerometer. As far as the volume and cost are concerned, the accelerometer is superior to the gyroscope. So, gyroscope-free inertial navigation technology comes as a research hotspot since the late 20′th century. Both linear motion and angular motion of a vehicle are measured by acclerometers at the same time in a gyroscope-free inertial navigation system (GFINS).

Hongjin Zhou, Yunhai Zhong, Hui Song, Su Wang

Chapter 3. Initial Alignment of GFINS

All of the inertial navigation systems are dead reckoning systems via integration computation based on the initial condition. The initial condition is a prerequisite and one of the key factors affecting the INS accuracy. Initial alignment is a process to establish initial conditions for the INS; it is one of the key technologies necessary to realize inertial navigation. GFINS self-dependent alignment technology and external information-aided alignment technology are studied.

Hongjin Zhou, Yunhai Zhong, Hui Song, Su Wang

Chapter 2. Gyro-Free Inertial Navigation Principle

This Chapter introduces the basic principle of gyroscope-free inertial navigation, including the principle to measure the angular parameters of a rigid body with the lever-arm effect, the setting scheme of the accelerometers, and the gyroscope-free inertial measurement unit (GFIMU) manufactured by the author’s team.

Hongjin Zhou, Yunhai Zhong, Hui Song, Su Wang

Traditional and Technical Assets of Punjabi Culture: Phulkari, Bagh and Chope Embroideries

Three traditional folk embroideries: Phulkari, Bagh and Chope of undivided Punjab, practised then by a group of females of similar or different age groups (Trinjan) in their homes are nowadays kept as heirlooms. These technique for these embroideries employ untwisted flat Silk floss to embroider on hand-spun cotton fabric and have been enriching the cultural fabric of various life-cycle ceremonies followed in Punjab. Ceremonial Phulkari, Bagh and Chope had a ‘Nazar battu’ (to ward away the evil eye) of different colour and motifs, and the presence of this motif defines the authenticity of home-crafted folk embroidered fabric. This paper will bring forth authentic traditional methods of identifying these heirlooms. The tradition to embroider with Silk floss was an essential merit for a would-be bride of Punjab, so that they become self-sufficient, learn about family affairs while sitting in a group of friends and elders. This cultural activity cultivated habit to maintain art in dressing themselves and it was customary to own Phulkaris, Baghs or Chope for a would-be bride. Besides the common visual material identity of traditional Phulkari, Bagh and Chope, they differ in visual and technical methods of embroidery, the details are discussed in the paper. Also, each and every motif Embroidered on them narrates the embroiderer’s meticulous skills expressing their immediate environment, belief system, which makes every piece unique and reflection of individual’s family background, skills, prefrences, taste and liking. This paper primarily presents methods of visual and technical identification of traditional Phulkari, Bagh and Chope. It further highlights traditional belief, material culture and emerging trends.

Maneet Kaur

Investigation of Flammability Parameters of Different Types of Fabrics Using Digital Image Processing Technique

Fabric flammability is one of the most important criteria for the wearer safety. The basic objective of the apparels is to provide the basic protection to environmental conditions. But the modern age garments must also define the personality of the wearer. The textiles are also used for various purposes like home furnishing and bedding, transport, civil engineering, medical and defense. So the capacity of the burning of flammability must be evaluated at the manufacturing stage. Hence, researchers have been trying to determine the flammability capacity by measuring different flammability parameters like ease of ignition, the rate and extent of flame spread, the duration of flaming, measurement of heat release and heat of combustion. These flammability parameters are to be tested as per the numerous existing standards. These existing test methods are based on the manual measurement, which leads to human error at different stages of testing. So this project aims to determine the key flammability parameters like burning time, burning rate, burning area, char length and the complete thermal profile of the burning sample by using image processing technique. The measurement has been done by developing a customized vertical flammability tester and capturing the videos of the burning samples and then processing the videos by using customized developed software in MATLAB platform. The flammability parameters have been evaluated for the 100% cotton fabrics, 100% polyester fabrics and blends of the cotton and polyester fabrics. These fabric flammability parameters are compared for safe use in apparels. It is observed that the cotton fabrics are most safe for apparels whereas the 100% polyester fabrics are most dangerous in nature.

Ajit Kumar Pattanayak

Doodling: Introducing Paper Art into Textiles

The present study “Doodling: Introducing paper art into textiles” involves the collection of student scribbled designs from students’ notebooks. A market survey was conducted for the selection of product range. Sourcing of suitable fabric was done in which different fabrics were evaluated by panel of judges. For selection of background colour for blending, six different colour themes were created and evaluated by judges. A total 10 ranges were designed inspired from students scribbled designs. For selection of ranges, ranges were evaluated by panel of judges. Documentation of both scribbled and developed designs was done. Selected ranges were constructed into final products. Market and consumer acceptability were done and responses from both for living area range were found appreciable, very innovative, unique and exclusive. The objective of dissemination of the gathered data was achieved by conducting workshops for students on doodling art. The workshop conducted received positive responses and ample interest was shown by students for attending more such programs.

Rashi Garg, Anila

Optimization of Fusing Process Conditions Using the Response Surface Design

In this investigation, optimization of fusing conditions to minimize the shrinkage and maximize the bond strength between a fabric and a fusible interlining before and after the dry-cleaning process has been carried out using the response surface design. To optimize the quality of fused specimens, most important fusing parameters such as fusing time and fusing temperature were selected. Woven interlining was fused on men’s shirting fabric by varying fusing time (10, 12, 14, and 16 s) and temperature (120 ℃, 130 ℃). As per the standard, fusing pressure of 1.5 bar was kept constant. After fusing, the fused fabric was characterized for different properties. Obtained results were analyzed by factorial analysis method. Findings of this will help garment manufacturers in selecting the optimum fusing conditions so that they can maintain the cost and quality of the product at the same time.

Ashish Hulle, Ravikumar Purohit

Sustainable Dyeing of Wool by Natural Dyes in Conjunction with Natural Mordants

Indians are known as precursors in natural dyeing art. Even though home-grown knowledge mode has been experienced in the past over the years but applications of natural colourants have been reduced due to lack of methodical knowledge of extraction, dyeing procedures and documentation over generations. This leads to failure to commercialisation of natural colourants. All the synthetic colourants being used for dyeing textiles now a days have dire environmental concerns due to their toxicity and non-biodegradability. They generate water pollution, are carcinogenic along with waste disposal problems. Natural colourants are rational solution to all these problems. Thus, it is obligatory to evolve suitable technology for extraction and sustainable applications of natural dyes on textiles. Present study is an approach to extract natural colourants from a variety of plants sources such as Kalanchoe-pinnata, papaya, peepal and banyan using specific extraction techniques to achieve maximum yield in K/S and antioxidant properties. These four natural extracts were tested for their dyeing potential on wool fabric. Dyeing was performed using three different mordanting techniques (pre, meta and post-mordanting) wherein different natural mordants such as harda, amla, pomegranate and orange as well as synthetic mordants such as alum, copper sulphate and ferrous sulphate were used to fix dye on to the textile substrates. A rainbow of natural colours was obtained with varied shades of each colour. Finding of the study shows that all the four natural extracts give satisfactory wash and light colour fastness. The natural mordants give comparable results with synthetic mordants. Thus these natural extracts along with natural mordants can be explored at industrial scale for sustainable colouration of wool.

Neetu Rani, Lalit Jajpura

The Effect of Wet Processing on the Comfort and Mechanical Properties of Fabrics Made from Cotton Fibres and Its Blends with Modal and Tencel Fibres in Weft

In this modern era, customers demand improved functional fabrics along with some other properties. The product developments can be done in various methods; the blending of various fibres to make fabric with enhanced properties is one of them. The wet processing can affect the comfort properties of fabrics made out of different fibrous material. Here, the effect of wet processing (scouring and dyeing) was studied on the comfort and other properties of plain-woven fabrics made using weft of 100% cotton, 50:50 cotton/tencel and 50:50 cotton/modal blend was studied. The results reveal that the air permeability decreases in all samples (100% cotton fabric, cotton/modal blended fabric and Tencel/cotton blended fabric) after scouring but no significant change has been seen after dyeing. The overall moisture management capacity increases significantly in all samples after scouring and further increases after dyeing. Fabric strength increases after scouring and decreases after dying. The fabric bending modulus decreases after scouring in all fabric samples and there is not significantly change has been seen after dyeing.

Devanand Uttam, Garima Ahlawat

Manufacturing Technologies and Scope of Advanced Fibres

Fibres form the basic identity of textiles. These are not confined merely to apparel and household textiles (traditional uses) these days; rather have been recognized as advanced fibres in the field of technical textiles. Different sectors of technical textiles, viz., automotive, medical, geo-textiles, agro textiles and protective clothing, etc. need specific properties for functionality purposes in textile fibres. To cater to the stringent requirements for these specialized applications and the quest to produce sustainable innovative products in respective fields, the world has seen a paradigm shift in the technology and growth of advanced fibres. However, these advanced fibres come with several advantages and disadvantages––defining their scope and limitations––and therefore, provide a room for further research in technological developments pertaining to their manufacturing technologies. This paper focuses on the details of the scope of these advanced fibres and related technological advancements/innovations, which will be worthwhile to provide a window to carry out further research in this area.

Amal Chowdhury, S. Dhamija

Studies on the Water Retention Properties of Coir Needle Punched Nonwovens

Natural fibers like coir, kenaf and cotton are biodegradable and eco friendly. The effective utilization of the natural fiber in different filed of applications is gradually increasing due to the environment friendliness. Needle punched nonwoven samples was developed with coir/cotton and coir/kenaf fibres with 90/10 blend ratio. The areal density of the needle punched nonwovens is 950 g per square metre and thickness of the samples is around 15 mm. The water holding capacity of the samples was tested at different time levels (5–45 min). Water retention property of soil with and without needle punched nonwoven bed was tested with different time levels. The effect of coir/cotton and coir/kenaf fibres-based needle punched nonwovens with soil on plant growth also studied. The results show that, the water holding capacity % of the coir/cotton needle punched nonwoven is 35.34% and the coir/kenaf needle punched nonwoven are 22%.

J. C. Sakthivel, L. Sivashankar

Effect of Aerosol Charging on Energy Consumption During Pulse Jet Filtration Using Conductive Media

Energy consumption is an important aspect for any industry which directly relates to its profit margin. In the present study energy consumption during filtration of conductive filters has been analyzed at different dust charge levels on laboratory-based pulse jet system assisted with pre-charger. Five types of polyester conductive material viz. PTFE coated media, Stainless Steel Fibre blended with PET media, Stainless Steel Scrim media, Carbon Fibre blended with PET media and Carbon Filament Scrim Media have been characterized at three different charge levels viz. 4, 8, and 12 kV, and without charge. The results showed that there is a significant drop in consumption of energy with the increase in pre-charging. Energy consumption results were further compared with full scale bag house condition by calculating the power utilized for 100 bags. The outcome revealed that among all the materials the performance of PTFE coated media is the best and role of material is most significant toward the energy consumption by the filtration system. Overall energy consumption is reduced with the increase in charge level in the pre-charger. It has also been noted that percentage contribution of energy consumption for fan energy is much higher for full scale bag house as compared to flat media test rig. While for compressor energy, the difference in percentage contribution is comparatively less and for energy due to charge, there is not much variation in percentage contribution.

Arunangshu Mukhopadhyay, Sudev Dutta, A. K. Choudhary, C. C. Reddy

Impact of Demonetization on Textile and Apparel Industry

Demonetization drive has directly or indirectly affected the entire Indian textile and apparel industry, but the major impact of demonetization on Micro Small and Medium Enterprises (MSME) and the unorganized sector is evident. MSME sector of the textile industry is majorly driven by the contractual labor as well as a daily wager. Due to the cash crunch, textile and apparel industry was unable to pay wages and meet daily expenses for running their mills. The negative effects of demonetization are workforce layoff, closure of small units, reduction in manufacturing activities, increase in production cost, rise in raw cotton prices in some areas. The positive outcomes are that cashless transaction has been increased significantly and around 5 lakhs bank accounts have opened in the major textile clusters like Tirupur, Surat, Ludhiana and Bhiwandi. The major objective of this review is to study the impact of demonetization drive on the textile and apparel supply chain.

Anju Choudhery, Kiran Choudhery, Varinder Kaur, Parambir Singh Malhi, Sachin Kumar Godara

Design and Development of Smart Sportswear Integrated with Energy Harvesting Device

Fashion and apparel industry has been witnessing a lot of transitions in past few decades with clothing not merely regarded as an entity for protection and self-adornment but the whole concept has been reformed with the inception of smart wearable technologies becoming an integral part of today’s fashion parade. Sportswear is one such highly innovative and functional class of clothing which involves a lot of fiber, yarn and fabric engineering to match the needs of a sportsperson. The basic requirement of sportswear is comfort to the wearer along with easy mobility. Comfort can be engineered into sports textile by the selection of such fiber, yarn and fabric variables that contribute to effective thermal, moisture vapor and liquid moisture transmission through clothing. Furthermore, there has been a quest for enhancing the functionality and performance of sportsperson and monitoring their physiological parameters via specifically engineered and designed sportswear. The present study has been undertaken to integrate the concept of smart wearable technology into sportswear intended for sportsperson indulging in low to dynamic physical activity. Accordingly, a sportswear assembly comprising solicit-sports panel integrated t-shirt, shorts, wristband and baseball cap have been designed and developed to explore the moisture management properties desirous of sportswear and energy harvesting principle of solar panel (via its integration into sportswear). The moisture transmission properties of different knit structures have been analyzed and based on objective evaluation; the most suitable structure has been selected for the design and development of sportswear. The designed sportswear has been incorporated with energy harvesting device and the smart sportswear so developed is subjectively tested and evaluated in real time situations.

Yamini Jhanji, S. Khanna, A. Manocha

Leveraging Artificial Intelligence to Foster Innovation and Inclusive Growth in the Textile Value Chain

No country in the world today, developed or developing, can afford to overlook the critical advantages of Artificial Intelligence (AI) for sustainable economic growth and innovation. Beyond nations, the same argument applies to the manufacturing sector. Innovation creates wealth and improves overall quality of life, which is a legitimate expectation of a citizen of any country. AI is set to become the next frontier of innovation as the cost of computing power becomes increasingly affordable. AI’s impact will be immensely beneficial provided the right regulatory framework (privacy and security) and policies (labour, education & training, re-skilling, etc.) are implemented to sustain the AI ecosystem.

Satyadev Rosunee

Thermal Contact Properties of Rib Cotton Weaves at Increased Moisture Level

Due to lower contact area with a skin, rib woven fabrics such as corduroy exhibit relatively good thermal insulation and dry thermal contact properties, but after their use under certain physical effort, moisture will reduce level of their wearing comfort. In the study, the effect of the relative width of the ribs and absorbed moisture on their thermal resistance and thermal absorptivity was investigated. As expected, fabrics with lower contact area exhibit good thermal properties even at the fabric relative moisture 20%.

Lubos Hes

Localized Compression Clothing for Improved Sports Performance

Compression sportswear worn by elite athletes to enhance performance is based on compression therapy which was widely used for treating venous disorders. Recent research with athletes has shown that compression garments may provide ergogenic benefits for athletes during exercise by enhancing lactate removal, reducing muscle oscillation and positively influencing psychological factors. This study reveals the performance evaluation of a localized compression garment developed with varying pressure at different areas of the body. Different composition of compression fabric made of polyester microfiber, lyocell and elastane has influence on the generated interfacial pressure. It is observed that with increase in elastane % and elastane stretch, the fabric becomes compact and thick with higher thermal resistance and reduced permeability to air and moisture vapour. As the elastane % increases, the moisture content, spreading area and drying rate are higher but the wickability is lower. During field trial, usage of medium and higher elasticity fabrics showed a reduction of 90% in the muscle movement as analyzed through EMG. The experiment resulted with 9% increase in the performance of the volunteer during running and cycling. Hence, it is more advantageous to wear compression garments, where less muscle activation occurs thereby enhancing athletic performance.

P. Kandhavadivu, D. Gopalakrishnan

The Effect of Structural Parameter on Pressure Behaviour of Tubular Bandage

Compression therapy is the most widely used treatment for venous leg ulcer (VLU), and it has been utilised in different forms for more than four centuries. There are wide varieties of compression bandages available for the treatment of various diseases. A suitable regime has to be selected for the specific problem based on required pressure level. In this paper, a study was conducted on the pressure behaviour of single jersey tubular bandage by varying the Lycra Denier (20, 30, 40 denier), stitch length (mm) in the structure at different limbs circumference (20, 30, 33 cm) on an artificial limb layered with foam of different hardness (10, 20 and 30). The effect of parameters both individually and interactively on the pressure performance of tubular bandage was statistically analysed. As compared to other constructional parameters, stretch (%) of tubular bandage has the most significant impact in generating required bandage pressure. From ANOVA analysis it is concluded that stretch (%) has almost 40% contribution in imparting overall bandage pressure whereas stitch length, lycra denier and limb hardness has 20%, 20% and 16% contribution respectively.

Monica Sikka, Mamta Devi, Samridhi Garg

Zea Mays Husk Reinforced Epoxy Composites

This work is focused to explore the potential of zea mays husk (ZMH) as reinforcement in the thermosetting polymer composite. Most of the work that had been carried out globally on zea mays stover is especially on zea mays husk and that too primarily for ethanol production and upto some extent as reinforcement for composite fabrication after fiber extraction. A novel effort has been made to use ZMH in film form for reinforcement. Araldite epoxy resin and hardener are used as matrix and pretreated ZMH as filler to form the laminate composites. The effect of alkali treatment conditions on ZMH is optimized in terms of ZMH and the respective composite properties. Characterization of ZMH is carried out by XRD, SEM and mechanical properties. ZMH laminate composites are also characterized with SEM and DMA. SEM images confirmed the partial delignification of ZMH after pretreatment. Fractured samples of composite reinforced with NaOH treated ZMH evidenced good interphase between matrix and filler as compared to neat epoxy. DMA test showed effectiveness of ZMH reinforcement in matrix. Flexural modulus of ZMH reinforced composite is found to be 3.45 GPa as compared to 2.43 GPa for neat epoxy composites.

Harwinder Singh, Arobindo Chatterjee

Surface Modified Hollow Polyester/Polyvinylpyrrolidone Composite for O2 Enriched Air Separation

Oxy-rich air is required for many industries for various processes. Mixture of pure oxygen with air is a costly process where oxy-rich air is required. In this research an attempt has been made by a novel technique such as preparation of activated carbon/PVP blended polymer loaded, surface modified hollow polyester fibre composite for the production of oxy-rich air. The PVP and activated carbon has an advantage of higher O2 permeability and O2/N2 selectivity. Surface modified hollow fibre is used to enhance the air separation rate. An experimental plan has been developed for the construction of composite with NaOH treatment time, concentration of PVP and concentration of activated carbon as independent variables. Fifteen set of experiments have been derived with independent variables and composites were prepared as the plan. The effect of independent variables on oxygen enrichment and air separation rate is analysed in detail. Highest oxygen enrichment percentage as 38.62 was achieved by 3 h NaOH treated, 15% PVP and 4% activated carbon loaded composite. The highest rate of air separation was given by 3 h NaOH treated, 10% PVP and 4% activated carbon loaded composite.

N. Gobi, A. Ganesh, E. Anbu, N. Agalya

A Novel Approach in Dyeing of Cotton Fabric Without Salt

Textile dyeing is a complicated process involving the addition of a large number of dyes and auxiliaries to achieve the exact shade. The wastes generated in this process are huge and polluting to the land and the surrounding environment. The main cause of this effluent problem happens to be the addition of salt in reactive dyeing. Hence rather than finding a method to dispose these hazardous wastes generated it would be better to devise a safer system of dyeing. Salt is inevitable in the conventional method because it masks the zeta potential developed by cotton fabric when immersed in water. This masking of the zeta potential facilitates the negatively charged dye to get attracted to the fabric. But the same effect can be produced with the help of electric current by passing positive charges to the fabric. The quality parameters, such as K/S value, fastness and uniformity, of fabric dyed with help of electrical current is also similar to that of fabric dyed using conventional method. By doing this the TDS content of the effluent is greatly reduced and reduces sludge formation. This also poses a chance for reuse of dye liquor which will minimize the consumption of dyes and reduce cost. It also has an ease of implementation in all dyeing units by slight modification of the present working style.

M. Senthilkumar

A Novel Approach Towards Design and Development of Indian Men’s Workplace Casual Footwear with Specific Reference to Sizing

In Indian footwear sector, casual footwear involves those preferred by people for daily wear in schools, colleges or workplace, etc. Casual footwear dominates the market followed by mass footwear. The common styles of men’s workplace casual footwear are moccasin, boot, derby, oxford, brogue, sneaker and gore shoe. While footwear size is obviously important, we tend to overmagnify its importance by the assumption that if the footwear is the right size it will automatically deliver proper fit. From the stand point of the fitter, footwear size consists primarily of two measurements: overall length and ball width. These measurements however do not indicate the true size of the foot or the footwear. Heel width, waist girth, instep, heel to ball, arch length also come in “sizes”. The footwear is presumably “sized” in its various sections to match the corresponding sections of the foot. Thus, the primary objective of the research is to assess lasts of Indian men’s workplace casual footwear including aspects like match of toe shapes and redesign of lasts along with fitness assessment and other aspects closely related to long-term comfort which may be considered in order to improve model accuracy. In order to achieve this demographic and morphological characteristic of feet of subjects belonging to Delhi NCT region were collected. Morphological characteristics were collected using SATRA foot measurement system. Since styles of workplace casual footwear includes boots, certain anthropometric dimensions of the leg were also collected using the procedure outlined in ISO 8559:1989(En) standards.

Sivasakthi Ekambaram, Chitra Arora

Influence of Weft Density on Runoff Erosion Control Performance of Rolled Erosion Control Systems

Rolled erosion control systems (RECSs) used in erosion control application mitigates runoff erosion through micro-barriers created by cross-laid weft yarns of RECS. Increase in number of cross-laid weft yarns (weft density) of RECSs is expected to improve its performance, so coir and jute RECSs with different weft density were prepared and evaluated for erosion control performance and germination performance. Runoff erosion test was performed in a bench-scale setup designed based on ASTM D 7101 standard, at zero and soil infiltration condition (with and without soil), at three different slope angles of 15°, 30°, and 45°. Whereas, germination test was performed using earthen pots and wheat seeds, based on ASTM D 7322 standard. Increased weft density resulted in improved performance of jute RECSs at all slope angles and infiltration condition, due to increased storage volume and better drapability. But the performance of coarser yarn count coir RECSs reduced at higher slope angle, due to increased flexural rigidity. In germination test, increase in weft density of finer yarn RECSs resulted in improved total rooting and percentage of vegetation, due to lower flexural rigidity and higher moisture holding. Whereas in coarser yarn RECSs, increase in weft density resulted in decreased total rooting and percentage of vegetation. It was also observed that the jute RECSs facilitates faster initial growth and highest total rooting as compared to coir RECSs due to finer and soft jute fibers that facilitate easy vegetation growth and better moisture-holding capacity.

Vinay Kumar Midha, S. Suresh Kumar

Kapitel 6. Synchronmaschine

In diesem Kapitel werden die bereits aus dem Buch „Elektrische Antriebe—Grundlagen“ [Sch94; Sch00a; Sch07b; Sch09b; Sch13] bekannten Gleichungen sowie Signalflusspläne der verschiedenen Ausführungsformen der Synchronmaschinen kurz dargestellt. Um den Einstieg auch in diesem Buch zu ermöglichen, sei u. a. auf Kap. 4.1.1 auf Seite 404 (Drehfeldmaschine allgemein) und auf Kap. 4.1.2 auf Seite 405 (Raumzeigerdarstellung) hingewiesen, die wesentliche Grundlagen für das Verständnis enthalten.

Dierk Schröder, Joachim Böcker

10. Ausgewählte Anwendungen

In Produktionsanlagen mit kontinuierlicher Fertigung werden Stoffbahnen verschiedener Materialien wie Metalle, Kunststoffe, Textilien oder Papier erzeugt und in unterschiedlichen Sektionen bearbeitet. Der Aufgabe entsprechend durchlaufen die Stoffbahnen dabei verschiedene Bearbeitungsschritte mit elastischen oder plastischen Verformungen, Beschichtungen oder speziellen Behandlungen. Am Ende der Bearbeitung werden die Stoffbahnen meist in Wickeln gespeichert.

Dierk Schröder, Joachim Böcker

Chapter 8. Conclusion: Contributions, Impacts and Recommendations for Future

This chapter summarises the study findings for each main task stated in Introduction chapter. The chapter includes four main sections, justification of how the main tasks are delivered, contributions to knowledge, implications on the practice, and recommendations for the future work.

Saleh Seyedzadeh, Farzad Pour Rahimian

Chapter 7. Modelling Energy Performance of Non-domestic Buildings

This chapter presents an energy performance prediction model for the UK non-domestic buildings supported by machine learning. The aim of the model is to provide a rapid energy performance estimation engine for assisting multi-objective optimisation of non-domestic building energy retrofit planning. The study lays out the process of model development from the investigation of requirements and feature extraction to the application on a case study. It employs sensitivity analysis methods to evaluate the effectiveness of the feature set in covering retrofit technologies. The machine learning model which is optimised using advanced evolutionary algorithms provides a robust and reliable tool for building analysts enabling them to meaningfully explore the expanding solution space.

Saleh Seyedzadeh, Farzad Pour Rahimian

Chapter 6. Building Energy Data-Driven Model Improved by Multi-objective Optimisation

This chapter proposes a method for optimising ML models for forecasting both heating and cooling loads. The technique employs multi-objective optimisation with evolutionary algorithms to search the space of possible parameters. The proposed approach not only tunes single model to precisely predict building energy loads but also accelerates the process of model optimisation. The chapter utilises simulated building energy data to validate the proposed method, and compares the outcomes with the regular ML tuning procedure (i.e. grid search). The optimised model provides a reliable tool for building designers and engineers to explore a large space of the available building materials and technologies.

Saleh Seyedzadeh, Farzad Pour Rahimian

Chapter 4. Machine Learning for Building Energy Forecasting

In recent years, Artificial Intelligence (AI) in general and Machine Learning (ML) techniques in specific terms have been proposed for forecasting of building energy consumption and performance. This chapter provides a substantial review on the four main ML approaches including artificial neural network, support vector machine, Gaussian-based regressions and clustering, which have commonly been applied in forecasting and improving building energy performance.

Saleh Seyedzadeh, Farzad Pour Rahimian

Chapter 3. Multi-objective Optimisation and Building Retrofit Planning

This chapter, first, reviews evaluation indices for the efficient retrofit plan to enhance building energy performance, second, provides the concept and mathematical demonstration of multi-objective optimisation (MOO) and finally presents the potential of using MOO for supporting the development of retrofitting strategies.

Saleh Seyedzadeh, Farzad Pour Rahimian

Chapter 2. Building Energy Performance Assessment Methods

Buildings are responsible for a vast amount of GHG emission. Therefore, most countries have set regulations to decrease the gas emission and energy consumption of buildings. These regulations are diverse targeting different areas, new and existing buildings and usage types. This paper reviews the methods employed for building energy performance assessment and summarise the schemes introduced by governments. The challenges with current participates are discussed and solutions will be recommended.

Saleh Seyedzadeh, Farzad Pour Rahimian

Chapter 1. Introduction

In the UK, buildings are responsible for 46% of all carbon dioxide ( $$CO_2$$ C O 2 ) emissions [20]. This figure is 40% in the USA and 27% in Australia [15]. Accordingly, the enhancement of energy efficiency of buildings has become an essential matter in order to reduce the amount of gas emission as well as fossil fuel consumption. An annual saving of 60 billion Euro is estimated as a result of the improvement of EU buildings energy performance by 20% [21].

Saleh Seyedzadeh, Farzad Pour Rahimian

Chapter 5. Machine Learning Models for Prediction of Building Energy Performance

This chapter investigates the accuracy of most popular ML models in the prediction of building heating and cooling loads carrying out specific tuning for each ML model and using two simulated building energy data. The use of grid search coupled with cross-validation method in examination of the model parameters is demonstrated. Furthermore, sensitivity analysis techniques are used to evaluate the importance of input variables on the performance of ML models. The accuracy and time complexity of models in predicting heating and cooling loads are demonstrated.

Saleh Seyedzadeh, Farzad Pour Rahimian

Chapter 6. Hollow Magnetic Nanoparticles

Hollow magnetic nanoparticles present a characteristic morphology that gives rise to interesting magnetic behaviors and novel applications. In this chapter, we describe the synthesis methods utilizing the Kirkendall effectKirkendall effect and the magnetic properties of these nanoparticles, with a focus on the analysis of their enhanced surface anisotropySurface anisotropy, spin disorderSpin disorder, and exchange biasExchange bias effect. The experimental studies are complemented by atomistic Monte Carlo simulationsMonte Carlo Simulations. Finally, we review a variety of applications of these nanoparticles, especially in biomedicineBiomedicine, batteries, sensing, and data storageData storage, and also discuss some of the limitations that need to be overcome for their implementation.

Hafsa Khurshid, Zohreh Nemati, Óscar Iglesias, Javier Alonso, Manh-Huong Phan, Hariharan Srikanth

Chapter 17. Nanocomposites for Permanent Magnets

Permanent magnets are exploited in a variety of devices (e.g. motors, generators, sensors, actuators) used in various fields of applications including transportation (e.g. (hybrid)electric vehicles), energy management (wind turbines…) and information technology (e.g. hard disc drives). Permanent magnet research today is concerned with improving the performance of magnets based on various hard magnetic phases while reducing dependence on any critical materials used. Nanocomposite magnets which combine a high coercivity hard magnetic phase with a high magnetisation soft magnetic phase hold great potential to rise to this challenge. In this chapter, we briefly outline the history of permanent magnets and explain the basic physical concepts behind nanocomposite permanent magnets. We recall the metallurgical and physical vapour deposition synthesis routes used to fabricate bulk and thin film nanocomposites, respectively. We then focus on chemical synthesis methods which offer the possibility to produce hard and soft magnetic nanoparticles or core-shell nanoparticles that can be used as building blocks to fabricate bulk hard-soft nanocomposites. We present three case studies concerning the fabrication and structural and magnetic characterisation of FePt-Fe3Pt, FePd-Fe and SmCo5-Fe nanocomposites. We wrap up the chapter with an outline of the challenges faced in producing hard-soft nanocomposite magnets using chemically synthesised nanoparticles, and an overview of the advanced magnetic characterisation tools being used to study the complex magnetisation reversal processes at play in hard-soft nanocomposites.

Isabelle de Moraes, Nora M. Dempsey

Chapter 4. Core/Shell Bimagnetic Nanoparticles

The advances in the physical and chemical fabrication methods have enabled the possibility to produce artificial nanostructures whose properties are different from that of their constituent materials. The presence of interfaces in core/shell bimagnetic nanoparticles introduces additional interactions that could radically modify the static and dynamic magnetic behavior of the systems. The number of parameters that governs the magnetic behavior grows enormously and the opportunity to manipulate, control, and understand the role played by each one of them, opens a wide range of possibilities to design novel materials with suited properties. The magnetic response changes depend on the magnetic ordering and anisotropy of the phases, the core size and shell thickness, the quality of the interface, and the strength of the interface exchange coupling. In this chapter, we discuss the new properties found in core/shell bimagnetic nanoparticles and analyze the main characteristics that have to be taken into account to design a system with a particular response.

Elin L. Winkler, Roberto D. Zysler

Chapter 12. Magnetic Force Microscopy and Magnetic Nanoparticles: Perspectives and Challenges

Among the various techniques for the characterization of magnetic NPs, magnetic force microscopyMagnetic Force Microscopy (MFM) (MFM) represent one of the most widespread and versatile methods due to its lateral resolution, sensitivity, imaging capability, the need for a relatively simple and widespread experimental setup, minimal/no specific requirements about sample preparations, capability to operate in air at room conditions as well as in vacuum or liquid environment. Indeed, MFMMagnetic Force Microscopy (MFM) enables the quantitative characterization of magnetic properties of single magnetic NPs, can be used to detect single magnetic NPs in nonmagnetic (e.g., polymeric or biological) matrices, as well as to perform mechanical or magnetic nanomanipulation of single NPs. In this chapter, applications of MFMMagnetic Force Microscopy (MFM) in the study of magnetic NPs are briefly reviewed and intriguing perspectives are depicted, focusing on current limitations to overcome and challenges to take up.

Daniele Passeri, Livia Angeloni, Marco Rossi

Chapter 11. Electron Tomography

The recent advances in TEMTransmission Electron Microscope (TEM) instrumentation with faster and more sensitive detectors, and the ever-increasing number of advanced algorithms capable of achieving quality 3D reconstructions with fewer acquired projections, are transforming electron tomography in one of the most versatile tools for a materials scientist, as the possible field of application for this technique is open to virtually any nanoscaled material. The complete three-dimensional characterization of magnetic nanoparticlesMagnetic-NPs is not an exception. Not only the 3D morphology is resolved, but also the elemental composition in 3D, by combining the available reconstruction algorithms and TEMTransmission Electron Microscope (TEM) spectral characterization techniques, seeking to retrieve the so-called spectrum volumeSpectrum-volume. Among them, electron energy loss spectroscopy (EELSElectron Energy Loss Spectroscopy (EELS)) stands out, given its unchallenged lateral resolution and its unique ability to resolve variations of the oxidation states, and even atomic coordination, through the analysis of the fine structure of the elemental edges in the acquired spectra. This chapter is a revision of electron tomography strategies applied to magnetic nanomaterials, beginning in a chronologically ordered description of some of the commonly used algorithms and their underlying mathematical principles: from the historical Radon transformRadon-transform and the WBPWeighted Back-Projection (WBP), to the iterative ARTAlgebraic Reconstruction Techniques (ART) and SIRTSimultaneous Iterative Reconstruction Technique (SIRT) algorithms, the later DARTDiscrete Algebraic Reconstruction Technique (DART) and recently added compressed sensing-based algorithms with superior performance. Regarding the spectral reconstruction, dimensionality reduction techniques such as PCAPCA and ICAIndependent Component Analysis (ICA) are also presented here as a viable way to reduce the problem complexity, by applying the reconstruction algorithms to the weighted mappings of the physically meaningful resolved components. In this sense, the recent addition of clustering algorithms to the possible spectral unmixing tools is also described, as a proof of concept of its potentiality as part of an analytical electron tomography routine. Throughout the text, a series of published experiments are described, in which electron tomography and advanced EELSElectron Energy Loss Spectroscopy (EELS) data treatment techniques are used in conjunction to retrieve the spectrum volumeSpectrum-volume of several magnetic nanomaterials, revealing details of the NPs under study such as the 3D distribution of oxidation states.

P. Torruella, J. Blanco-Portals, Ll. Yedra, L. López-Conesa, J. M. Rebled, F. Peiró, S. Estradé

Chapter 10. Measuring Atomic Magnetic Moments in Magnetic Nanostructures Using X-Ray Magnetic Circular Dichroism (XMCD)

The chapter describes the development of X-ray magnetic circular dichroism (XMCD) using circularly polarised soft X-ray photons from synchrotron sources. Following the derivation of X-ray absorption sum rules for magnetic materials, the technique became a powerful probe of magnetism able to separately measure the atomic and spin orbital magnetic moments independently for each magnetic element in the sample. The majority of the experiments have focused on the L-absorption edges of transition metals and the method has been particularly useful in identifying the source of enhanced magnetic moments in nanostructures. The chapter illustrates the power of the method with a specific example, that of Fe@Cr core–shell nanoparticles with different Cr shell thicknesses. Here, it was shown that at least two Cr atomic layers are required to see the onset of the exchange bias effect at the ferromagnetic–antiferromagnetic interface. The future perspectives of the technique are described including spatially resolved XMCD and time-resolved XMCD measurements.

Chris Binns, José Angel de Toro, Peter Normile

Chapter 15. Smart Platforms for Biomedical Applications

This chapter provides an overview of the various types of magnetic micro- and nanoparticle systems used in biomedical applications. We broadly divide particle types into colloidally synthesized and lithographically defined on silicon wafers. The applications relevant to each particle type are highlighted followed by research case studies. Each case study highlights a novel approach to the engineering of magnetic particles for a specific application. Finally, future perspectives for the field are described with an emphasis on the challenges remaining to be solved for all the main application areas of magnetic particles.

Tarun Vemulkar, Russell P. Cowburn

Chapter 5. Magneto-Plasmonic Nanoparticles

Magnetoplasmonics nanoparticles encompass in a single nano-entity all the rich science and promising applications of the plasmonics and magnetic nanoworlds. The difficult liaison and a certain incompatibility between plasmonics and magnetic phenomena, due to the different chemical-physical origins and supporting materials, are overcome thanks to the design and synthesis of novel nanostructures. The variations of properties, interactions and synergies of both phenomena and materials demonstrate how rich and surprising the matter is at nanoscale and the promising applications. In fact, we show how not only light and magnetism can interplay but also other phenomena like forces, heat, electric field and chemical interactions, between others, can show synergism. Magnetoplasmonic systems are excellent benchmark materials to develop and investigate multi-responsive multifunctional nanosystems that now are required in an increasing number of technologies, such as biomedicine, pharmacy, catalysisCatalysis, optoelectronics and data storage.

César de Julián Fernández, Francesco Pineider

Chapter 9. Magnetism of Individual Nanoparticles Probed by X-Ray Photoemission Electron Microscopy

Magnetic nanoparticlesMagnetic nanoparticle are of great interest for applications in fields ranging from biomedicine to spintronics. However, despite considerable work, their size-dependent magnetic properties are still poorly understood. In this chapter, we will introduce x-ray photoemission electron microscopy (XPEEM)X-ray Photoemission Electron Microscopy (XPEEM) as a spectromicroscopy technique ideally suited for the investigation of the magnetic properties of large numbers of individual nanoparticlesIndividual nanoparticles in extended ensembles. Moreover, XPEEM can be combined with other microscopy techniques to achieve a direct correlation between magnetism, size, shape, and structure of the very same nanoparticles. This approach has led to the discovery of novel magnetic states in 3d transition metal3d transition metal nanoparticles characterized by strongly enhanced magnetic energy barriersMagnetic energy barrier, attributed to the strong impact of structural defectsDefects rather than to surface or interfaceInterface contributions to the totalMagnetic anisotropy magnetic anisotropy.

Armin Kleibert

Chapter 16. Magnetic Fluids for Thermoelectricity

The unique properties of magnetic nanoparticles (MNP) and their interactions with their environment have given rise to innovative R&D possibilities outside the field of conventional magnetism. One such example is in the field of energy science, and in particular, the thermal engineering. In this respect, research on refrigeration technology based on the magnetoconvection property of ferrofluids (FF) has attracted great attention in the past decades. On the other hand, the thermoelectric energy conversion (or more commonly known as “thermopower”) in ferrofluids has so far remained underexplored. This subchapter describes this very new research path in the field of magnetic nanoparticle science, from its theoretical background and motivation, a few existing example of experimental investigations and the future perspectives. TheThermoelectricity unique properties of magnetic nanoparticlesMagnetic nanoparticle (MNP) and their interactions with their environment have given rise to innovative R&D possibilities outside the field of conventional magnetism. One such example is in the field of energy science, and in particular, the thermal engineering. In this respect, research on refrigeration technology based on the magnetoconvection property of ferrofluidsFerrofluids (FF) has attracted great attention in the past decades. On the other hand, the thermoelectric energy conversion (or more commonly known as “thermopower”) in ferrofluidsFerrofluids has so far remained underexplored. This subchapter describes this very new research path in the field of magnetic nanoparticleMagnetic nanoparticle science, from its theoretical background and motivation, a few existing example of experimental investigations and the future perspectives.

Sawako Nakamae

Chapter 8. Magnetic Self-Assembling of Spherical Co Nanoparticles Used as Building Blocks: Syntheses, Properties and Theory

In this chapter, we show that thanks to the use of micellar and organometallic approaches, one can favor the growth of uniform spherical Co NPs with controlled surface passivation (dodecanoic acid or oleylamine), tunable size (from around 4 to 9 nm) and tunable nanocrystallinity (from fcc to hcp structure). As a result of the balance between van der Waals attractions between the metallic NPs, magnetic interactions between the magnetic NPs and solvent-mediated interactions between ligands, these uniform colloidal NPs can be used as building units to form a full set of assemblies which morphology depends on the deposition strategy, involving solvent evaporation. In the case of spontaneous self-assembling of magnetic NPs, compact hexagonal 2D arrays and 3D superlattices called supercrystals can form. In the latter case, either face-centered cubic supercrystalline films or single colloidal crystals can be obtained. Mesostructures of hexagonally ordered columns, labyrinths and void structures can result from assisted self-assembling, induced by the application of an external magnetic field. In highly ordered superlattices, individual NPs act as “artificial atoms” and occupy the lattice sites to form repetitive, periodic “artificial planes". From a fundamental point of view, these artificial solids constitute good models for investigating crystallization behavior. Resulting from collective interactions between neighboring NPs, they exhibit novel magnetic properties. The magnitude of these interactions, and then, the magnetic properties, can be tuned by various parameters including (1) the (crystallographic) nature of the magnetic NP, (2) the NP size, (3) the nature of the coating agent, (4) the nature of the solvent, (5) the evaporation rate and (6) if appropriate, the application of an external field during the solvent evaporation. On the one hand, simulations based on a flory-type solvation theory using Hansen solubility colloidal parameters allow to predict the cobalt NP size. On the other hand, Monte Carlo simulations and free energy theories are able to predict the size and type of patterns appearing during the evaporation of a solution of magnetic NPs under a magnetic field.

Johannes Richardi, C. Petit, Isabelle Lisiecki

Chapter 14. Medical Applications of Magnetic Nanoparticles

The increased ability in manipulating matter at the nanoscale has paved the way towards the creation of a plethora of novel systems endowed with extremely appealing properties exploitable in a wide number of clinical applications, the two most prominent being, undoubtedly, Magnetic Resonance Imaging (MRI) and Magnetic Fluid Hyperthermia (MFH). In this Chapter, we review a few recent examples to convey to the reader a picture of the promising role magnetic nanoparticles (MNPs) may play in the medicine of the next future. After a general overview of the two techniques, we summarize the physical principles at their base to provide the reader the necessary tools to understand limits and advantages of employing MNPs as contrast agents in MRI and heat mediators in MFH. Among the countless examples of MNP-based materials proposed in the recent years for these applications, we select and report in detail some of the most representative and promising ones to underline the challenges that this branch of the material science must address to interplay with the complexity of the human body. Finally, we try to photograph the state of the art of the clinical applications, which, mainly concerning MFH, is in continuous evolution.

Matteo Avolio, Claudia Innocenti, Alessandro Lascialfari, Manuel Mariani, Claudio Sangregorio

Chapter 3. Collective Magnetic Behaviour

The mechanisms responsible for magnetic interaction between nanoparticles are described and modelled in the previous chapter of this book. Here, the collective superspin glassSuperspin glasses state resulting from such interaction is discussed, using a collection of experimental results. Superspin glassesSuperspin glasses display qualitatively similar dynamical magnetic properties as canonical spin glassesSpin glasses, including ageing, memory and rejuvenationRejuvenation phenomena. In the Introduction, the dynamical properties of spin and superspin glassesSuperspin glasses are illustrated and contrasted. These properties are discussed in more detail in Case studies, taking into account the nanoparticle concentration, size and size distribution, using results from studies of ferrofluidsFerrofluids and compacts of γ-Fe2O3Γ-Fe2O3 particles. The Outlook section illustrates recent findings suggesting that the temperature dependence of the low-field isothermal remanent magnetizationIsothermal Remanent Magnetization (IRM) (IRM) and magnetization as a function of magnetic field (hysteresis or M-H) curves of superspin glassesSuperspin glasses include information on the superspin dimensionality and magnetic anisotropyMagnetic anisotropy. The possibility to engineer nanocompositesNanocomposites with tailored magnetic interaction and anisotropy is also discussed.

Roland Mathieu, Per Nordblad

Chapter 13. Magnetic Nanoparticles for Life Sciences Applications

The ongoing research on the applications of magnetic nanoparticlesMagnetic nanoparticles in Bio-medicine and the results obtained up to now open a wide range of possibilities for their use in Life Science disciplines, for example in general plant research and agronomy. The work presented here focuses on the interaction of two types of magnetic core-shellCore-shell nanoparticles with plants and microorganisms. The research carried out with carbon coated ironIron nanoparticles aims to investigate their penetration and translocation in whole living plants and into plant cells, as response of the nanoparticles to magnetic field gradients. This study is essential to evaluate the suitability of any nanoparticles as magnetic responsive carriers for the localized delivery of phytosanitary or pest control treatments. The study carried out with silicaSilica coated nanoparticles focuses on their interaction with fungal cells, taking a soil borne plant pathogenPlant pathogens as in vitro model. Our research paves the way to use magnetic nanoparticlesMagnetic nanoparticles for detection, selective control and eventual elimination of pathogenic fungi.

C. Marquina

Chapter 7. Nature Driven Magnetic Nanoarchitectures

Magnetotactic bacteria are aquatic microorganisms that have the ability to align in the geomagnetic field lines, using a chain of magnetic nanoparticles biomineralized internally (called magnetosomesMagnetosomes) as a compass needle. Here we describe the biogenesis of magnetosomes, focusing in the formation of the mineral core. We then discuss the magnetic properties of the magnetosomes and the chain of magnetosomes, a natural paradigm of a magnetic 1D nanostructure. Finally, we review the use of magnetosomes and magnetotactic bacteriaMagnetotactic bacteria in biomedical and biotechnological applications, with special mention to the application in magnetic hyperthermiaMagnetic hyperthermia treatments.

María Luisa Fdez-Gubieda, Lourdes Marcano, Alicia Muela, Ana García-Prieto, Javier Alonso, Iñaki Orue

Chapter 2. Interparticle Interactions: Theory and Mesoscopic Modeling

In this chapter, we discuss the interparticle interactionInterparticle interaction effects in assemblies of magnetic nanoparticlesMagnetic nanoparticles. For our study, we have developed a mesoscopic scale model that takes into account: (a) the morphology of the assemblies and (b) the interplay between the interparticle and intra-particle characteristics of the nanoparticles. The hysteresis loopsHysteresis loop, the virgin magnetization curvesVirgin magnetization curves and the temperature-dependent (Field CooledField-Cooled magnetization curve (FC) (FC)/zero-field cooled (ZFCZero-Field-Cooled magnetization curve (ZFC))) magnetization curves have been calculated with our model. Results are presented for three case studies of different nanoparticles’ morphologies assemblies and they show that our mesoscopic modelMesoscopic model reproduces well the experimentally studied systems and reveals the origin of the observed magnetic behavior.

Marianna Vasilakaki, George Margaris, Kalliopi Trohidou

Chapter 1. Single Nanomagnet Behaviour: Surface and Finite-Size Effects

InFinite-size effects this chapter we discuss some intrinsic features of nano-scaled magnetic systems, such as finite-size, boundary, shape and surface effectsSurface effects. We mainly review in a succinct manner the main results of previous works. We first present the basics of theoretical models and computational techniques and their applications to individual nanomagnets. Results of both simulations and analytic calculations for specific materials, compositions and shapes are given based on these models.

Òscar Iglesias, Hamid Kachkachi

Parallelized Numerical Optimization for Parameter Fitting of an Advanced Elasto-Viscoplastic Model with an Open Source Implementation

To model the elasto-viscoplastic soil response, even in one-dimensional problems, a significant amount of parameters are required. These parameters interact, making it difficult to fit the parameters directly. A model is fit to data by numerical optimization with a number of local and global algorithms. The evaluation showcases that the correct parameters can be found efficiently by optimization, but that there is a significant risk of converging to a local minimum far removed from the correct solution as the dimensionality increases. A randomly repeated local search algorithm is proposed which outperforms the other algorithms. The optimization scheme was applied to find the parameters based on tests with varying stress paths on the same soil by a combined parallelized optimization scheme. The combined optimization allows to find parameters that fit all stress paths as good as possible, serving as a basis for comparison of models.

Thomas Alexander Vergote, Leung Chun Fai, Chian Siau Chen

Analysis of Cone Penetration Using the Material Point Method

This paper presents preliminary results from the numerical simulation of cone penetration in Tresca material. The simulations were performed using two variations of the generalized interpolation material point method (GIMP), uniform GIMP and contiguous particle GIMP. A moving-compressible structured irregular background grid with adaptive material point splitting was used for computational efficiency. The non-linear B-bar method was used for mitigating volumetric locking. The obtained results were compared with results published in the literature to illustrate the efficacy and accuracy of using the proposed numerical scheme.

Vibhav Bisht, Rodrigo Salgado, Monica Prezzi

Overcoming Volumetric Locking in Three-Dimensional Material Point Analysis

The material point method is ideally suited to modelling large deformation problems in three dimensions, especially in cases where the finite element method struggles due to mesh distortion. However, when the method is used to analyse problems with near-incompressible material behaviour, such as in geotechnical engineering using models with isochoric plastic flow, it suffers from severe volumetric locking. This causes the method to over predict the forces for a given displacement and induces spurious stress oscillations through the problem domain. Several methods have been proposed in the finite element literature but few of these have been applied to the material point method. In this paper we present a way to avoid volumetric locking for three-dimensional material point analyses with simplex elements (linear tetrahedra) using an $$ F $$ F bar patch approach. Not only does the technique avoid the over-stiff behaviour associated with volumetric locking but it also reduces the stress oscillations in the method, which are often attributed to cell-crossing instabilities. The formulation is validated against two three-dimensional benchmark problems.

William M. Coombs, Lei Wang, Charles E. Augarde

Molecular Origin of Compressibility and Shear Strength of Swelling Clays

Swelling clays are found all over the world, and the damage caused to the infrastructure in swelling clay areas is estimated to be about 20 billion dollars annually in the United States. Compressibility and shear strength are critical properties of soils that are necessary for the design of infrastructure. Our group has shown that molecular interactions between clay and fluids have a dramatic impact on the macroscale properties of swelling clays. The permeability of the clay increases about 500,000 times when the permeating fluid in the Na-montmorillonite clay is changed from polar fluid water to low polar fluid. This change results from clay–fluid molecular interactions as well as the differences to the microstructure caused by these interactions. In the current work, the compression and shear strength of the clay interlayer is studied by changing the polarity of the fluid in the interlayer and applying compressive and shear stresses using steered molecular dynamics. The results show the strong influence of normal stress as well as fluid polarity on compressibility and shear response of the clay at the molecular scale. The results demonstrate that clay–fluid molecular interactions play a crucial role in the macroscopic compressibility and shear strength of swelling clays.

Dinesh R. Katti, Keshab B. Thapa, H. M. Nasrullah Faisal, Kalpana Katti

Evaluation of Seismic Response of Rectangular Underground Structures in Liquefiable Soils

The evaluation of the seismic response of underground structures is an important step in its design. Currently, displacement-based pseudo static methods are one of the most popular class of methods recommended by several design guidelines and codes. However, in this study, through comparisons with dynamic finite element method analysis using advanced soil constitutive models, we show that the application of the simplified displacement-based method in liquefiable soils is inappropriate. The seismic response of a typical rectangular section underground structure in non-liquefiable and liquefiable ground using linear elastic model and the unified constitutive model for large post-liquefaction deformation of sand, respectively. A displacement-based pseudo static method is then used in these two scenarios, using input from free field analysis. Comparisons between the results from the two types of analysis methods show relatively good agreement for the non-liquefiable ground scenario. Whereas for the liquefiable ground case, the displacement-based method significantly underestimates the deformation and internal forces of the structure. This is shown to be caused by the ineptness of the displacement-based pseudo static method in taking into consideration the spatial non-uniformity of structure and near field soil seismic response in liquefiable ground. This study highlights the importance of advanced constitutive modeling of soils in practical geotechnical earthquake engineering applications.

Tong Zhu, Rui Wang, Jian-Min Zhang, Hexin Liu

Effectiveness of Using Polymer-Modified Asphalt Binders in Enhancing Fatigue Life of Asphalt Mixes Containing RAS and RAP

In view of its environmental and economic benefits, the use of Recycled Asphalt Shingles (RAS) and Reclaimed Asphalt Pavement (RAP) in Hot-Mix Asphalt (HMA) is on the rise. However, concerns over premature cracking and reduced fatigue life have limited their use in HMA. Polymer-modified asphalt binder is known to enhance the fatigue performance and resistance of HMA to cracking. This study was undertaken to evaluate the effectiveness of using a polymer-modified asphalt binder in asphalt mixes containing RAS and RAP to reduce fatigue cracking. For this purpose, two sets of HMA mixes, one set with a non-polymer-modified and the other set with a polymer-modified asphalt binder, both having identical gradations containing equal amounts of RAS and RAP were designed and tested for fatigue using a four-point bending beam method. It was found that polymer-modified asphalt binder effectively improved fatigue life of HMA mixes containing RAS, RAP, and their combinations. Also, use of RAP and a combination of RAS and RAP in asphalt mixes containing both non-polymer-modified and polymer-modified asphalt binders improved their fatigue lives. However, using only RAS resulted in an adverse effect relative to fatigue performance.

Rouzbeh Ghabchi, Musharraf Zaman, Dharamveer Singh, Manik Barman, David L. Boeck

A Critical Review of the Effect of Temperature on Clay Inter-particle Forces and Its Effect on Macroscopic Thermal Behaviour of Clay

The effect of temperature on the mechanical behaviour of geomaterials is relevant in a number of geotechnical applications including low enthalpy energy geostructures. Mechanical response of clays upon heating is not always intuitive, and this includes the volumetric ‘collapse’ observed in normally consolidates clays. This paper reviews the effect of temperature on clay particle interaction forces (Colombian, van der Waals and mechanical) in the attempt to elucidate the micro-mechanisms underlying temperature-induced behaviour observed at the macroscale.

A. Casarella, M. Pedrotti, Alessandro Tarantino, Alice Di Donna

Multiphasic Approaches for Estimating THM Properties of Heterogeneous Rocks

The estimation of the Thermo-Hydro-Mechanical (THM) properties of heterogeneous rocks is influenced by the scale of the heterogeneity in relation to the dimensions of the test specimen, which will enable the testing of a suitable representative volume element. This places constraints on the testing techniques and the problem can be compounded when the rock has low permeability that presents challenges for saturation of the rock and required time for conducting basic tests to evaluate the deformability and transport properties relevant to fluid flow and heat conduction. The paper proposes the use of multiphasic techniques estimating THM properties of the heterogeneous Cobourg limestone.

A. P. S. Selvadurai

Consolidation of Saturated Soils through a Different Prism

The founding principles of consolidation of soils was set by Terzaghi dating back to 1923. This theory focused on the interplay between pore pressure dissipation and effective stress increase on fully saturated soils, and works by means of the diffusion theory in one-dimensional flow conditions under constant static external loading. The theory remains to use still and works as the funding stone for all subsequent formulations in the international theory. It is noted, that all consolidation formulations reduce to the original Terzaghi’s theory (as they comprise its extensions) for one-dimensional flow under constant static loading on fully saturated conditions. This paper revisits the consolidation theory and derives the governing equations via a rigorous integration of mass conservation, which accounts for instantaneous void ratio alterations within the continuity equation by including an additional term in the consolidation coefficient. This gives shorter consolidation times compared to Terzaghi’s original expression. The derived equations reduce to Terzaghi’s with appropriate manipulation. The paper compares the 1D consolidation coefficients to Terzaghi’s and other formulations, and proposes a simplified solution of the consolidation equation based on regression, accompanied with a workaround to include the rigorous approach in commercial (FEM, FDM) codes within the consolidation governing equations.

A. Kalos, G. Belokas, A. Anagnostopoulos

A Continuum Viscous-Elastic-Brittle, Finite Element DG Model for the Fracture and Drift of Sea Ice

The thin layer of ice covering the polar oceans is a complex geomaterial that is constantly breaking and moving under the action of the wind and ocean currents and that experiences transitions between a brittle solid and a granular fluid state. We have developed a simple continuum mechanical framework in the view of representing accurately its dynamical behavior in regional and global sea ice or coupled climate models. It combines the concepts of elastic memory, progressive damage and viscous-like relaxation of stresses. Here, we present this framework and its ongoing numerical development based on Finite Element, Discontinuous Galerkin methods.

Véronique Dansereau, Jérôme Weiss, Pierre Saramito

Mathematical Modeling of Water Infiltration in Unsaturated Latosol Samples

Understanding the soil in the unsaturated state means, among other things, understanding how the presence of water transiently affects the physical and hydraulic properties of the soil environment. This is extremely important in solving soil resistance problems involving water, such as the stability of land slopes. Among the hydraulic properties that are essential in understanding water flow in porous media, flow velocity and soil water retention capacity are the most important defining characteristics of the hydraulic behavior of the medium. In the physical model used in this study, these characteristics were represented by the advective velocity and hydraulic diffusivity parameters that were obtained from the infiltration data by conducting tests on the latosol columns. The main results obtained can be used for the estimation of the wetting front advance given the uncertainties of the variables obtained from the confidence envelope curves.

Patricia Figuereido de Sousa, João de Mendonça Naime, Silvio Crestana, André Luís Brasil Cavalcante

Failure Analysis for Geo-Hydrologic Design

Groundwater abstractions may lead to structural failure of buildings due to the settlement of the subsurface. In order to set the probability of failure to a predefined acceptable level, a probabilistic procedure is proposed in this article. The procedure provides intervention levels for groundwater heads at which the extraction of groundwater should be reduced. As part of the procedure a Levenberg-Marquardt method, extended by a subspace regularization technique, calibrates a finite element method based groundwater model that simulates flow under natural conditions or at moderate extraction rates. The method provides expected values for geo-hydrologic parameters like transmissivity and flow resistance and expresses the parameter uncertainty in a covariance matrix. A first order reliability method uses these values and calculates the failure probability conditioned for a series of intervention levels. This paper outlines the procedure and presents the results of a verification test. A pumping test near Utrecht in the Netherlands is used to simulate a field scale application. The application shows that the procedure reduces the risk of failure to an acceptable level.

John van Esch, Bert Sman, Hans van Meerten, Rob Brinkman

3-D Particle Simulation Model for Weathering Processes of Geomaterials Under a Wet-Dry Cyclic Condition

This study presents a 3-D particle simulation model based on the discrete element method for the weathering processes of geomaterials. We modeled their properties of swelling and shrinking by changing the diameter of spherical region which is consisting of clay minerals and several sand particles. A series of simulations of deformation of mudstone under wet-dry cyclic condition was performed so that the applicability of the proposed model can be validated.

Y. Fukumoto, S. Ohtsuka

Clay Micromechanics: An Analysis of Elementary Mechanisms of Clay Particle Interactions to Gain Insight into Compression Behaviour of Clay

The macroscopic response of geomaterials is controlled by the processes occurring at the microscale. Understanding these processes is key to interpret experimental data, understand fundamental modes of stress-strain behaviour, inform ‘continuum’ macroscopic constitutive models, and develop quantitative predictive tools based on Discrete Element Method (DEM) approaches. Unlike granular materials, mechanisms at the particle scale controlling macro-mechanical behaviour of clays are still largely ignored. This paper presents an analysis of elementary mechanisms of clay particle interactions with the aim of gaining an insight into behaviour of clay and advance the process of defining suitable contact laws to be implemented into DEM formulations.

Alessandro Tarantino, A. Casarella, M. Pedrotti, Alice Di Donna, A. Pagano, B. de Carvalho Faria Lima Lopes, Vanessa Magnanimo

An Elasto-Plastic Framework for the Chemo-Mechanical Behavior of Low to Medium Activity Clays

Pore fluid composition strongly influences the mechanical behavior of clays, impacting both on their volumetric and shear response. Accounting for this aspect is crucial for engineering applications where changes of the chemical composition of the pore fluid are anticipated, such as transport through engineered barriers for the containment of pollutants, or slope stability of natural formations rich of clay minerals subjected to freshwater infiltration. In this work, a chemo-mechanical model capable of reproducing the response of medium to low activity clays under both mechanical and chemical loading paths is presented. The model is developed starting from the interpretation of experimental evidences in an elastic-plastic framework. Chemo-mechanical coupling is introduced both in terms of stress variables and hardening law. In particular, the formulation is specialized to variations of salt concentration, introducing osmotic suction as a chemical stress variable. The model was implemented in a constitutive driver for the integration at the REV level of the incremental constitutive equations, thus allowing for its validation against literature data.

Giulia Scelsi, Gabriele Della Vecchia, Guido Musso

Numerical Modelling and Simulation of the Wheel Rotation Problems by the Material Point Method

Soil-wheel interaction has been one of the fundamental research subjects in the terramechanics field. In this study the material point method (MPM) formulation is extended for the performance and mobility of unmanned wheels rotating on the soil. A new contact approach is developed for fast contact detection between rigid wheel and deformable soil. In each time step, contact background nodes are detected to define the contact elements and subsequently to determine the contact soil material points. An equivalent contact length is associated to each contact soil point and soil-wheel reaction forces are calculated. For a given angular velocity, the dynamic momentum balances (linear and angular) are solved and the motion of the wheel points is updated accordingly. Numerical simulations of a typical wheel going over the cohesive soil are presented to demonstrate the capabilities of the new approach. The soil is simulated using Mohr-Coulomb constitutive model, and the wheel is assumed as solid rigid. The wheel can automatically rotate and move forward vertically according to the material properties and surface geometry. FEM simulations is also conducted to compare and validate the MPM simulation, showing that the proposed MPM wheel-soil model is effective in predicting the dynamic rotation problems.

Xiaorong Xu, Alba Yerro, Kenichi Soga, Mo Li, Feng Jin

Finite Element Simulations of Clayey Soil Ground with a Three-Dimensional Nonlinear Elastic Viscoplastic Model

This paper presents a study on numerical simulations of clayey soil using nonlinear elastic viscoplastic (EVP) model. The nonlinear EVP model is based on Yin (1999)’s nonlinear creep equation in which a creep strain limit is considered. The model in the general stress-strain condition is implemented by finite element program Plaxis and is used to simulate clayey soil under Berthierville embankment. Good agreement between simulated and measured settlements and excess pore pressure validates the feasibility of the nonlinear EVP model. Furthermore, a parametric study is presented to demonstrate the importance of creep strain limit.

Ze-Jian Chen, Wei-Qiang Feng, Jian-Hua Yin

A Coupled MPM–SPH Numerical Simulation for Fully Saturated Soil

The material point method (MPM) has recently been used to perform soil–water interaction analysis for fully saturated soil in geotechnical engineering. In MPM, to treat fully saturated soil, two types of discretization methods have been mainly used: the single point formulation and the double point formulation. The former discretizes the soil–water mixture with a single set of particles, whereas the latter discretizes the soil phase and the water phase separately by using different sets of particles. In both the discretization methods, the flux boundary condition is imposed on the background mesh nodes, and the prescribed pore water pressure boundary condition is directly applied to the particles. This is the reason behind the complexity involved in the setting of boundary conditions for the coupled MPM. To reduce this complexity, this paper presents a discretization technique that combines MPM with smoothed particle hydrodynamics (SPH). SPH is used for the discretization of the generalized Darcy’s law to impose the flux boundary condition directly on the particles. The proposed formulation is validated through the soil–water interaction benchmark problems: the consolidation problems of Terzaghi and Mandel–Cryer. The numerical results are in good agreement with the analytical solutions, which validates the proposed method.

Yohei Nakamichi, Shigehiko Sugie, Tomohide Takeyama

A Viscoelastic, Viscoplastic, and Viscodamage Constitutive Model of Salt Rock

Based on the effective stress concept of continuum damage mechanics (CDM) and the assumption of a small deformation, a constitutive model of salt rock coupling viscoelasticity, viscoplasticity, and viscodamage is developed based on the Kelvin-Voigt model, Duvaut-Lions model and viscodamage model. The constitutive model is calibrated by experimental data of salt rock to determine the viscoelastic, viscoplastic, and viscodamage model parameters. The verification indicated that this constitutive model can reasonably model the primary creep, steady-state creep, accelerated creep in constant stress loading. Based on user material subroutine UMAT in Abaqus software, a three-dimensional finite element implementation of this constitutive model is realized. The constitutive model can effectively simulate mechanical responses including the long-term time-dependent deformation and damage evolution of geological bodies of salt rock and successfully conduct stability evaluation and failure analysis of cavern of large time span. This will provide a safety guarantee for underground energy storage.

Jianqiang Deng, Yaoru Liu, Qiang Yang, Wei Cui, Yinbang Zhu

Water Migration Influence on Changes of Physical and Mechanical Characteristics a Clay Soil Under Triaxial Loading

To study the issue of moisture migration and density changes in the sample during the test, the authors conducted experimental studies on the changes in the clay soils physical and mechanical characteristics under triaxial compression conditions in various devices: cubic and cylindrical. Experimental studies conducted have made it possible to establish that the duration of the loading stage significantly affects the volume of the fluid being moved. It was established that regardless of the sample regime loading and the test equipment type, a complex stress state is formed in the sample, which contributes to the formation of different density and humidity zones. The dimensions of these zones, the soil density and humidity, its mechanical characteristics within the specified zones are not constant and change during loading. In the soil sample loading process, two mutually compensating processes occur. The first softening process is due to the formation of microcracks and macrocracks. Secondly, this is the process of hardening due to the restoration of water-colloidal bonds between the clay soil particles and the “healing” of defects. The hardening and softening of clay soil mechanism is established.

Ilizar T. Mirsayapov, Irina V. Koroleva

Large Deformation Analysis of Embankments Considering Liquefaction Using Material Point Method

A dynamic hydro-mechanical coupling analysis method using Material Point Method (MPM) and its applicability to liquefaction-induced large deformation problem are presented. Based on the u-p formulation, the governing equations comprise the equations of motion for the whole mixture and the continuity equation for the water phase, disretized by MPM and finite difference method, respectively. A cyclic elasto-plastic constitutive model is employed for simulating liquefaction behavior. As a numerical example, a river embankment mounted on liquefiable foundation ground is simulated using the MPM. Finite element analysis using the same governing equations and the constitutive mode is also presented for comparison. Evolution of pore water pressure and deformation mode are discussed. MPM more reasonably simulated large settlement and lateral flow of the river embankment and the flood channel induced by liquefaction than finite element method. In particular, MPM properly evaluated the large deformation-induced total stress changes which had a significant influence on the liquefaction behavior and subsequent deformation behaviors.

Yosuke Higo, Daichi Uchiyama, Naoya Hirota, Tomoaki Takeuchi, Ryosuke Kato

On Inception of Instabilities in Granular Media Across Length-Scales with Flexible Boundaries

Emergence of non-uniform deformation modes or instabilities often encountered in laboratory “single element” tests have been examined in this study across various “length-scales” of granular media viz, continuum, discontinuum and laboratory biaxial “element” test level. With inhomogeneity outset, the mechanical response no longer remains a true representation of the material behaviour. It rather portrays the system response with the boundary conditions and the evolving instabilities. Instability onset within a transient undrained continuum elastoplastic framework is found to be a mesh-dependent phenomenon. This “pathological mesh-dependency” of classical Cauchy continua is addressed with the aid of Level Set Discrete Element Modelling of Flexible Boundary (FB) Plane-Strain (PS) tests that takes into account the actual grain morphology into consideration. The micromechanical observations are found to be in good qualitative agreement with the macromechanical “element” response of FB-PS tests. Interestingly, the microstructural arrangement or the grain fabric acts as the triggering mechanism behind the shear strain aggregation in localized zones within the sand specimen. Alternately, the evolution of heterogeneities may be considered as “disturbances” diffused within the sand specimen that later manifest into localized zones of shear strain accumulation on gradual shearing.

Debayan Bhattacharya, Amit Prashant

Insights into Suction Caisson Installation Utilising the Material Point Method

There is an increasing interest to utilise suction caissons as foundations for offshore wind turbines. Significant research has been devoted to developing penetration prediction methods and to understand the in-service response under cyclic loading. However, the effect of the installation process on the state of the surrounding soil is less well understood, although it may affect the in-service performance, in particular under relatively low magnitude cyclic loading, which represents the majority of loading conditions experienced by an offshore wind turbine in the field. This is due to the complexity in modelling the problem, which includes very large deformations, seepage flow and soil-structure interaction. Novel approaches featuring the material point method and centrifuge test results evaluated with the particle image velocimetry post analysis are capable of visualising the mechanisms underlying suction caisson installation. The results aim to reduce existing uncertainties and provide confidence in suction caissons as a reliable foundation system for offshore wind applications.

M. Stapelfeldt, B. Bienen, J. Grabe

Application of Barodesy - Extended by the Intergranular Strain Concept

The intergranular strain concept allows a consideration of the deformation history of the soil in constitutive models. In this contribution this concept is applied on the constitutive model barodesy. This combination allows the usage of the asymptotic state boundary surface of barodesy, which helps to reduce the overshooting effects of the intergranular strain model. The finite element implementation of the model is presented, including a strength reduction procedure to calculate the overall factor of safety. The functionality of the model is verified in the simulation of the excavation of a construction pit. The influence of the intergranular strain concept on resulting deformations as well as on the calculated factor of safety is investigated.

Manuel Bode, W. Fellin, Gertraud Medicus

Multi-scale Study of Grain Crushing in Granular Soils

Grain crushing is a phenomenon occurring at the grain-scale along areas of stress or strain concentration where the stress imposed exceeds particle strength. The grain fragmentation determines fine generation and a local densification of the material, which may induce contractions, settlements, decrease of hydraulic conductivity, etc. This work reports the results of a wide experimental program aimed to link the macroscopic behavior of granular materials subjected to oedometric compressions to grain crushing accounting for the micro-structural features of the single grains, e.g. size and shape. The grain scale was assessed by the use of the X-ray tomography facilities to characterize the material and quantify what is occurring along deformation. Tests performed included one-dimensional compression tests on dry samples till high pressure (~50 MPa) in order to observe significant amount of crushing. The material adopted is the Light Expanded Clay Aggregate (LECA), an artificial granular material characterized by light, porous and crushable grains. The compressibility curves has been linked to the grain crushing phenomena upon loading. The beginning of comminution is ruled by the strength of the single particle and by the initial assortment of size and shape. As the micro-structure influences the grain crushing and the material response, vice versa the grain crushing influences particles size and shape. The collected experimental evidence is finally used to develop a simple constitutive model able to predict the evolution of material porosity with loading.

Giulia Guida, Francesca Casini

New Advances in Strain Localization Analysis: Application to Seismic Faulting and Compaction Banding

Strain localization zones in the form of shear bands or compaction bands in geomaterials are observed across scales from sub-millimetric (grain size) to kilometric scale (geological structures). Triggering and evolution of such narrow zones of localized deformation depend on many factors. The mechanical behavior of geomaterials is central for the formation of such zones. However, thermal, pore-pressure and chemical effects play a crucial role in shear and compaction banding. Moreover, the inherent heterogeneous microstructure of geomaterials plays a significant role during strain localization. As for faults, compaction bands significantly influence the stress field and fluid transport. In this paper, we shall review some recent advances in experimental testing and numerical modelling on strain localization in geomaterials. The effect of grain crushing as observed in deformation bands under high confinement can be introduced by combining Breakage models and higher order continuum theories leading to a new framework of constitutive models with evolving microstructure. A major difficulty of these models is to establish reliable methods for the calibration of the higher order parameters (such as the internal length) in laboratory experiments. An example of a direct calibration of these parameters based on Digital Image Correlation of images provided by X-Ray tomography is proposed for the study of compaction banding in a carbonate rock.

Jean Sulem

Cyclic Shear Behaviour of High Plasticity Cohesive Soil Subjected to Variation of Frequency and Amplitude

In many instances, saturated cohesive soils are subjected to various types of cyclic/dynamic loading conditions such as earthquake loading, blast loading, oceanic wave storms, machine vibrations and traffic loading, etc. All of these loadings are different based on the rate and magnitude of loading cycles. Hence, the aim of the current study is to evaluate the undrained cyclic shear behaviour of saturated Nagpur soil subjected to various loading conditions. A series of strain-controlled cyclic simple shear tests were carried out on the compacted specimens of Nagpur soil at varying shear strain amplitudes (γs = 0.25, 0.5, 1.5, 2.5, 3.75, and 5%) and loading frequencies (f = 0.1, 0.5, 1, and 2 Hz). The hysteresis response was analysed in terms of shear modulus and damping ratio variation along with cyclic stiffness degradation and cumulative strain energy dissipation. Shear modulus and damping ratio were found highest for specimens loaded at the highest frequency with the lowest excess pore pressure generation. Rate and magnitude of stiffness degradation were reduced with a decrease in shear strain amplitude. Dissipated cumulative strain energy was observed to be maximum for higher shear strain amplitude and rate of loading. The results indicated that the frequency and amplitude variation greatly influenced the hysteresis response of saturated Nagpur soil.

Naman Kantesaria, Ajanta Sachan

Multiscale Modeling of Anchor Pull-Out in Sand

Anchors are popular and economic solutions for onshore and offshore engineering to provide adequate resistance for structures. In anchor design, it is critical to evaluate the bearing capacity of soil in supporting an anchor and understand the underlying load-carrying and failure mechanisms. Herein we employ a newly developed multiscale modeling tool based on coupled MPM/DEM for large deformation problems to investigate the cross-scale behavior during the pullout of plate anchors. This multiscale approach invokes Material Point Method (MPM) to tackle the large deformation problems in macro-scale and employs Discrete Element Method (DEM) to reproduce the soil response in meso-scale. It helps bypass conventional phenomenological constitutive models while providing cross-scale information of any interesting macroscopic observations. In this study, the influence of relative density of sand and the embedment ratio on the behavior of anchors (e.g., bearing capacity of anchors, deformation patterns) is investigated by the coupled method. Mesoscopic data and analyses originated from particle scale interactions are provided in lieu of the variable failure patterns observed in soil around an anchor during the pull-out process.

Weijian Liang, Jidong Zhao, Kenichi Soga

Investigation of Parameter Influence on Damage Evolution via PD-FEM Coupling Method

Peridynamics (PD) has received more and more attention in dealing with discontinuous problems. In this theory, the crack initiates and propagates arbitrarily without any extra remeshing strategy or propagation criteria. To improve the deficiency of computationally more demanding, PD is coupled with the classical finite element method (FEM). One symmetric double notched tension test is taken to verify the effectiveness of PD as well as the coupling method. The influence of parameters on the damage evolution is investigated based on this tension test. It is found that PD is capable to describe the crack propagation process in elastic-brittle materials. The overall force-displacement response is influenced by the size of loading increment. Importantly, the structural response is sensitive to the horizon radius. The results are approximately convergent when the horizon radius is no less than three times the specific mesh size. For a particular (three times) ratio, the peak force and the peak displacement are negatively affected by the mesh size. The critical energy release rate positively influences the peak force as well as the peak displacement. The Young’s modulus has a positive effect on the peak force but the negative effect on the peak displacement.

Yao Yue, Fanyu Ming, Yue Tong, Wanqing Shen, Jianfu Shao

Use of Sand-Rubber Mixture (SRM)-Filled Trenches for Pile Driving Induced Vibration Screening

Pile driving induced vibrations creates a huge concern for the construction industry since it may cause damage to the surrounding structures or settlement of the soil, depending on the intensity of ground shaking or vibration. It is essential to estimate the transmitted vibration intensity to avoid structural damages, which are highly dependent on the physical properties of the pile and the soil that acts as the transmitting medium. One widely adopted solution for the screening of pile-driving induced ground vibration is the use of infill trench in the path of wave propagation. The high damping and energy absorption capacity of rubber is well established in the past, making it an ideal material in vibration mitigation studies. In this paper, the use of sand-rubber mixture (SRM) as a trench infill material has been investigated to understand its effect on reducing the response of impact pile induced vibrations to adjacent structures. The SRM-filled trench barrier was provided as a passive isolation system, and field tests were conducted to evaluate its vibration screening performance under impact loading due to piling. The outputs from the analysis, in the form of acceleration-time history and Peak Particle Velocity (PPV), was obtained on either side of the trench with and without SRM infill. Overall, SRM was found to have a better performance with regards to the attenuation of surface waves. Further, a considerable reduction in peak acceleration and PPV was noted due to the introduction of SRM-filled trench barriers.

A. Boominathan, J. S. Dhanya, P. J. Silpa

A Robust Implementation of Dynamic Evolution of Fluid-Driven Fractures

In this study, an energy based hydro-mechanical model and computational algorithm for the problem of hydraulically driven fracture networks developing in naturally fractured impermeable media is developed. The model is based on non-differentiable energy minimization for the dynamic deformation and fracture of the body coupled with mass balance of fluid flow within the hydro-fractures. Time-discontinuity induce spurious crack opening velocity fields which lead to nonphysical solutions for the coupled fluid pressure field defined locally along the crack faces. The use of a time-continuous fracture model, such as the present non-differentiable energy minimization approach, is crucial for the numerical soundness and stability of the hydraulic fracture propagation algorithm. A discontinuous Galerkin finite element formulation is implemented, in which every element edge in the mesh is a potential site of hydro-fracture initiation and propagation. The presence of pre-existing natural fractures, as a common challenge in nearly all geological formations, are modelled with desirable flexibility by simply assigning different fracture properties to the element edges defining the natural fractures. Using the graph theory principles, a search algorithm is proposed to identify, among all, the sub-set of cracked interfaces that form the interconnected hydraulically loaded fracture network. Robustness of the proposed computational algorithm and its versatility in the study of hydraulic fracturing are shown through several numerical simulations.

M. Vahab

Can LS-DEM be Used to Simulate Cyclic Behavior of Sand?

The suitability of LS-DEM to simulate drained and undrained cyclic behavior of sand is evaluated in this paper. A digital twin of a small specimen of the Hostun sand is used to simulate the cyclic average (macroscopic) response along idealized stress and strain paths, representing oedometer, drained and undrained triaxial conditions. The results are here only qualitatively evaluated based on comparison with real test data of different sands, since a) cyclic laboratory tests have not been performed on the actual specimen, and b) relatively low contact stiffness was used in this preliminary analysis in order to reduce the computational cost. The oedometer curves during virgin loading, unloading and re-loading and the cyclic secant stiffnesses during drained cyclic loading were captured qualitatively, but were significantly softer than the experimental ones. From the simulation of a drained cyclic triaxial test the development of accumulated volumetric strain seems reasonable, and the computed response during a cyclic constant volume (undrained) triaxial test looks very promising. Based on this initial study, more detailed LS-DEM simulations will therefore be carried out to improve the understanding of cyclic behavior of saturated sand.

Hans Petter Jostad, H. D. V. Khoa, K. Karapiperis, J. Andrade

Creep Effects on the Thermo-Hydro-Mechanical Responses of Callovo-Oxfordian Claystone

In France, a deep geological disposal for high-level radioactive waste (HLW) and intermediate level long life radioactive waste (IL-LLW) called Cigéo is planned to be constructed in a deep Callovo-Oxfordian claystone (COx) formation, if it is authorized. The heat emitted from the waste leads to a temperature increase in the low permeability host porous formation, which induces a pore pressure increase essentially due to the difference between the thermal expansion of the pore water and the solid skeleton. This study aims at assessing the effect of nonlinear behavior of COx, especially creep, on the THM response of the HLW repository. Different approaches, from perfectly Mohr-Coulomb model and simplified time-dependent models (power and Norton) to an advanced model, have been considered. These approaches lead to common conclusions that (1) the creep reduces the pore pressure increase compared to poro-elastic approach; (2) the nonlinear instantaneous response in the near-field resulting from cell drilling does not affect the THM response in the far field and (3) the thermal load does not induce any supplementary damage of the host rock.

M. N. Vu, M. Souley, M. Alonso, Jean Vaunat, Antonio Gens, C. Plua, C. De Lesquen, G. Armand

Elasto-Plastic Coupling in Soils: A Thermodynamic-Based Approach

In the present study the implications of a thermodynamic-based constitutive framework on the mechanical behaviour of soils are critically analysed. The primary advantage of this approach as compared to the traditional hardening plasticity is that the models are guaranteed to obey the laws of thermodynamics. Furthermore, the use of potential functions allows to introduce some crucial ingredients of the mechanical behaviour of soils that directly affect the shape of the yield surface and the flow rule of the model. To illustrate the above features, different forms of elasto-plastic coupling are presented and their implications on the response of the models are explored with reference to a series of numerical simulations.

Fabio Rollo, Angelo Amorosi

A Surrogate Model for Fast Land Subsidence Prediction and Uncertainty Quantification

Numerical modeling of anthropogenic land subsidence due to the exploitation of subsurface resources is of major interest to anticipate possible environmental impacts on the ground surface. The reliability of predictions depends on different sources of uncertainty introduced into the modeling procedure. In this study, we focus on reduction of model parameter uncertainty via assimilation of land surface displacements. A test case application on a deep hydrocarbon reservoir is considered where land settlements are predicted with the aid of a 3D Finite Element (FE) model. The calibration of the parameters defining the rock constitutive law is obtained by the Ensemble Smoother (ES) technique. The ES convergence is guaranteed with a large number of Monte Carlo simulations that may be computationally infeasible in large scale and complex systems. A surrogate model based on the generalized Polynomial Chaos Expansion (gPCE) is proposed as an approximation of the forward problem. This approach is expected to reduce the overall computational cost of the original ES formulation and enhance the accuracy of the parameter estimation problem. The result is compared with a posterior sampling by Markov Chain Monte Carlo (MCMC) to assess the quality of the assimilation.

Claudia Zoccarato, Massimiliano Ferronato, Pietro Teatini

Improved Contact Bond Model of Discrete Element Method for Simulating Strain Rate Effect of Rock Materials

When the discrete element method (DEM) is used to simulate rock dynamic experiments with split Hopkinson pressure bar (SHPB), it is difficult to obtain the result that the numerical and experimental rock specimen will have the same rapid growth of dynamic compressive strength when strain rate increases. To solve this problem, an improved contact bond model of DEM considering the crack propagation velocity was proposed. Then this new contact bond model was used to simulate the rock dynamic experiments with SHPB under different loading rate. Compared with the simulation results of the original contact bond model, the simulation results of this new contact bond model are closer to the experimental results.

Y. Zhao, G. Y. Zhao, J. Zhou

A Numerical Study on Controlling Parameters for Runout Distance of Landslides

Numbers of uncertainties are involved in slope stability analysis. In particular, when a slope fails, uncertainty of parameters of the slope will cause the variability of runout distance of sliding mass which decides the consequence triggered by landslides. In general, slope geometry parameters and residual strengths parameters are highly close to the runout distance of landslides. This paper aims to investigate the effect of residual strength parameters and initial geometry parameters on runout distance of landslides via material point method. To clearly indicate relation of runout distance and these parameters for different soil slopes, three kinds of slopes, i.e., slopes in single soil layer, slopes in weaker upper soil layer and stronger lower soil layer and slopes in stronger upper soil layer and weaker lower soil layer are studied. For the first and third kinds of slopes, it is found that runout distance has a good negative exponential law with residual strength parameters and has a significant linear increase trend with geometry parameters. For the second kind of slope, the decrease trend of runout distance with residual strength parameters is faster; The increase trend of the runout distance with slope gradient can be indicated well via sigmoid curve; There is also a good linear increase relation of the runout distance and slope elevation. Additionally, the relation between runout distance and slope elevation obtained via MPM in this paper is consistent with that based on the empirical method. The conclusions can provide reference for assessment and management of landslides risk.

M. Lu, B.N. Xiong, M. Zhou, J. Zhang

Three-Dimensional Constitutive Model for Dry Granular Materials Under Different Flow Regimes

The numerical simulations of granular materials, in the framework of continuum mechanics, is quite challenging since the constitutive model should be capable of reproducing the transition from solid- to fluid like regimes and vice versa.In this paper a constitutive model, valid under general three dimensional evolving conditions, and capable of describing the material response under both quasi-static and dynamic regimes is presented. The model is calibrated by employing a series of true triaxial DEM numerical simulations performed on a periodic cell. The comparison between model predictions and DEM results highlights that the capability of the constitutive relationship of taking into account the dependence of the mechanical behaviour of the dry granular material on Lode angle, strain rate, void ratio and confining pressure.

Irene Redaelli, Pietro Marveggio, Claudio di Prisco

Calibration of an Advanced Constitutive Model Through Direct Shear Test Results

In many geotechnical problems, failure conditions involve the formation of a narrow shear band where shear strains localize. In this study, the thickness of the shear bands was indirectly determined based on the results of constant normal load direct shear (CNL) tests carried out on sand specimens reconstituted at three different relative densities. The adopted procedure also allows to evaluate the soil deformations within the shear band and, thus, to correctly locate the critical state line in the compressibility plane. The results of the CNL tests were used to calibrate the Severn-Trent model, an advanced constitutive model proposed by Gajo and Wood, apt to well-reproduce the mechanical behaviuor of sands from small to large strain levels. The predictive capabilities of the model were confirmed by the good agreement with the experimental data obtained performing constant normal stiffness direct shear (CNS) tests. Finally, the shaft bearing capacity of a bored pile embedded in a homogeneous soil layer was numerically evaluated and compared to the one predicted using a less sophisticated (classical) approach.

G. M. Rotisciani, E. Natu, A. de Lillis, D. Sebastiani, Salvatore Miliziano

Influence of Heterogeneity on the Elastic Contact Problems in Geotechnical Engineering

Contact problems are widely encountered in geotechnical engineering, such as the contact between soils and the concrete slab in earth and rockfill dams, concrete lining in a tunnel and coastal levees. Due to the unknown contact region and contact forces, the contact problems have strong boundary nonlinearity. In addition, soils have been recognized as heterogeneous materials in geotechnical engineering, and the existence of the spatial variability of soils increases the nonlinearity of the problems. In order to investigate the influence of heterogeneity on the contact problems, the penalty method is used to analyse the contact problems. In this paper, Young’s modulus, is taken to be a spatially variable. Random field theory is used to model the heterogeneity of Young’s Modulus. The results showed that the influence of heterogeneity on the elastic contact problems is significant. In order to better predict the deformation/stress in the contact bodies, the spatial variability needs to be considered.

Kang Liu, Weihai Yuan, Yanqiao Wang

Numerical Manifold Method for Simulating of Multi-crack Propagation in Rock Mass

The expansion and penetration of the structural planes under stress is an important cause of rock mass failure. Based on the principle of linear elastic fracture mechanics, a multi-crack propagation simulation algorithm of higher-order numerical manifold method (NMM) is proposed. The singularity of the crack tip displacement field is considered by adding key terms of the crack tip displacement field function to the basis function of the NMM. The stress intensity factor at the crack tip was calculated by J integral. The cracking and propagation directions of I-II mixed cracks are judged by the maximum circumferential tensile stress criterion. Hypothesis-modified multi-crack propagation algorithm is used to solve the problem of multi-crack propagation. When a single physical cover contains two or more crack tips, the influence of the singularity of the displacement field at each crack tip will be considered simultaneously in the physical cover displacement function. For those integral functions which do not conform to the simplex integral form, Taylor series expansion method is used to calculate the approximate solution. The rationality and accuracy of the calculation method are verified by numerical simulation of two classical static crack propagation problems and physical model test.

Chunsheng Qiao, Zhiming Han

SODA: A Serial Fortran Library for Adaptation of Structured Meshes

It is often of great interest in geomechanical analysis to model localized phenomena, such as strain concentrations along failure planes or hydraulic gradient concentrations near discontinuities and exit points. Focus in recent years on massively parallel finite element codes with adaptive meshing algorithms, have left many previously developed libraries for adapting quadrilateral meshes difficult to find, and often unsupported. While large, parallel simulations are of great interest to researchers, an acceptable modeling outcome for many practical engineering problems can often be obtained using meshes with more modest numbers of elements (e.g. < 105), removing the need for use of large parallel libraries. This paper describes a software library written in modern Fortran for adaptive meshing of structured meshes. The library consists of less than 1,000 lines of code and is based on 4 Fortran functions making it quick to learn as an educational and research tool, and easy to implement in existing codes. The library is demonstrated through an example seepage problem of a point source (Poisson problem).

B. A. Robbins, D. V. Griffiths

On Validation of a Two-Surface Plasticity Model for Soil Liquefaction Analysis

Constitutive modeling of granular materials such as sands, non-plastic silts, and gravels has been significantly advanced in the past three decades. Several new constitutive models have been proposed and calibrated to simulate the results of various laboratory element tests. Due to this progress and owing to the surge of interest in geotechnical engineering community to use well-documented constitutive models in major geotechnical projects, a more thorough evaluation of these models is necessary. Performance of the current models should be particularly evaluated in the simulation of boundary value problems where stress/strain paths are much more complex than the element tests performed in laboratory. Such validation efforts will be an important step towards the use of these models in practice. This paper presents the results of an extensive validation study aimed at assessing the capabilities and limitations of a two-surface plasticity model for sands in two selected boundary value problems, i.e. lateral spreading of mildly sloping liquefiable grounds. The results of a large number of centrifuge tests conducted during the course of four consecutive international projects known as Liquefaction Experiments and Analysis Project (LEAP) are used in this validation study. The capabilities and limitations of the two-surface plasticity model, initially calibrated against element tests, will be carefully assessed by comparing the numerical simulations with the results of the centrifuge tests from recent LEAP projects.

Majid T. Manzari, Mohamed A. ElGhoraiby

Importance of Sand Fabric Anisotropy on the Bearing Capacity of Footings

Conventional design methods estimate the bearing capacity of shallow foundations by considering the soil as an isotropic elasto-plastic medium with an associated flow rule. State-of-the-art numerical analyses of such foundations employ constitutive models that consider strain softening and a non-associated flow rule if the soil is granular. Such analyses lead to increased accuracy over the conventional design methods, i.e. relatively lower bearing capacity, yet they do not consider the effect of soil fabric anisotropy. In order to investigate this effect, analyses of the bearing capacity of shallow foundations are carried out, by means of the finite difference method using the SANISAND-FR constitutive model that is fabric-based and verified against element and centrifuge test results. A comparison is made here between the analyses with this model and its variant that does not consider fabric effects, after their calibration to give identical results in the usually available triaxial compression tests. The comparison shows that neglecting sand fabric anisotropy, along with model calibration on triaxial compression tests, lead to an overestimation of the bearing capacity of footings, i.e. to un-conservative design.

Achilleas G. Papadimitriou, Yannis K. Chaloulos, Yannis F. Dafalias

Numerical Simulation of CPT with the Clay and Sand Model (CASM) Including Effects of Bonding

The simulation of cone penetration tests (CPT) poses still a challenge to numerical modelling because large deformations and large displacements have to be considered. In this work the Particle Finite Element Method code G-PFEM, which employs an updated Lagrangian description, is utilized. The use of linear elements in combination with a stabilized mixed formulation and frequent remeshing of critical regions ensures computational efficiency. The well-known Clay and Sand Model (CASM), which is a model based on critical state soil mechanics principles, has been implemented in G-PFEM and extended to account for effects of bonding and destructuration. Cone penetration in a low permeable silt under undrained conditions has been simulated and the influence of the degree of bonding and the rate of debonding on calculated cone resistance is evaluated. In an additional study the influence of the shape of the yield surface, which can be controlled by two input parameters in the model, on cone resistance is investigated.

Helmut F. Schweiger, Laurin Hauser

Effects of Pore Pressure on Wandering in Structural Natural Frequency

Natural frequency wandering is a phenomenon observed in dynamic structural behavior. Temporary and permanent changes in the determined natural frequencies have been shown to be related to such factors as weather conditions, structural damage or soil-structure interaction. Furthermore, some studies indicate temporary natural frequency wandering during seismic events. This temporary wandering and recovery of the initial pre-event natural frequency has not been specifically explained yet. Some studies indicate soil-structure interaction as a potential reason causing the observed structural behavior. This paper presents a numerical finite element study and aims at investigating the influence of soil-structure interaction on the observed natural frequency wandering induced by seismic actions. The advanced soil constitutive model Severn-Trent is used and an example structure built on saturated granular soil is analyzed. A temporary drop in the natural frequency is shown soon after the earthquake followed by regain to the initial value with time. The results show that generated pore pressure, its dissipation over time, reduced mean effective pressure and nonlinear stress-strain behavior are linked with temporary changes in natural frequencies.

Piotr Kowalczyk, Alessandro Gajo

Hydro-Mechanical Modelling of Multiphase Flow in Coalbed by Computational Homogenization

A multiscale model is developed for the modelling of coalbed methane (CBM) production. CBM recovery is known to be a highly coupled and multiphase problem. The finite element square method is used to integrate a fracture-scale model in a multiscale scheme. This method consists to localize the macroscale deformation to the microscale, then resolve the boundary value problem on the microscale with finite elements, then homogenize the microscale stresses to compute macroscopic quantities, and finally resolve the boundary value problem on the macroscale with finite elements. This approach has the advantage that it does not require to write some constitutive laws at the macroscale but only at the REV-scale. The multiscale model is therefore appropriate for reservoir modelling. The model is developed and implemented in a finite element code and the simulation of a synthetic reservoir is considered.

François Bertrand, Olivier Buzzi, Frédéric Collin

Reliability Analysis of Earth Slopes Using Direct Coupling

This paper shows how accurately and efficiently reliability analyses of geotechnical installations can be performed by directly coupling geotechnical software with a reliability solver. An earth slope is used as the study object. The limit equilibrium method of Morgenstern-Price is used to calculate factors of safety and find the critical slip surface. The deterministic software package Slope/w is coupled with the StRAnD reliability software. Reliability indexes of critical probabilistic surfaces are evaluated by the first-order reliability methods (FORM). By means of sensitivity analysis, the effective cohesion ( $$ c^{\prime} $$ c ′ ) is found to be the most relevant uncertain geotechnical parameter for slope equilibrium. The slope was tested using different geometries. Finally, a critical slip surface, identified in terms of minimum factor of safety, is shown here not to be the critical surface in terms of reliability index.

A. T. Siacara, G. F. Napa-García, A. T. Beck, M. M. Futai

Importance of Sand Fabric Anisotropy on Fault Rupture-Foundation Interaction

For the design of structures with shallow foundations in the vicinity of active faults sophisticated numerical analyses are a prerequisite. Current practice employs isotropic constitutive models for the simulation of the foundation soil layer. For enhanced accuracy, these models may also include strain softening, as well as a non-associated flow rule if this soil is granular, but the anisotropic nature of soils is not considered. In order to study how much sand fabric anisotropy affects the fault rupture-foundation interaction problem, this paper employs the finite difference method and 3 constitutive models of various complexity, including a new fabric-based model for sand named SANISAND-FR. All models are calibrated to give identical results under triaxial compression. The analyses show that the assumption of isotropy affects significantly the fault rupture–foundation interaction, and hence the expected response of the structure (e.g. rigid body rotation) due to rupture surfacing. This means that the design of structures against fault rupturing is of doubtful accuracy if models are used that do not consider sand fabric anisotropy.

Achilleas G. Papadimitriou, Yannis K. Chaloulos, Maria K. Dimoula, Yannis F. Dafalias

Bayesian Analysis, Multilinear Regression and Modern Machine Learning Algorithms Applied for Soil Probabilistic Characterization

Modern engineering problems are facing the growing demand to deal with huge amount of data and their intrinsic uncertainties. This exigence has led us to unprecedented insights and developments in the machine learning field. To date, the healthcare and financial sectors has been the precursor of practical application of machine learning approaches. In geotechnics and rock mechanics, the materials we deal with are characterized by a large amount of data, various levels of uncertainty and often a prior knowledge, therefore they lend themselves well to this type of analysis. This article aims to present Bayesian methods and machine learning algorithms applied for geotechnical characterization of soil and rocks. Once the test sample has been properly filtered and classified, we will demonstrate the potentiality of multivariate Bayesian linear regression as a main tool for dealing with multivariate data and uncertainty. In addition to frequentist approaches, we will make use of Bayesian models where the regression parameters, based on a prior distribution, will be calculated in terms of mean and variance.

Fabrizio Peruzzo

Random Field-Based Numerical Modeling of Deep Excavation in Soft Soils for Adjacent Building Damage Probability Assessment

In densely populated areas, it is common the need for using deep excavations for different infrastructure works, but they may cause excessive ground movements and generate damages to neighboring buildings. The analysis of deep excavations in soft soils is a complex problem in which the use of a combination of numerical and probabilistic techniques is useful to represent the behavior of such inherently variable deposits. In the numerical and probabilistic analysis, constitutive soil parameters can be treated as random fields to deal with uncertainty due to spatial variability. In this research, parameters E50ref and E0ref from the constitutive model Hardening Soil Small Strain are simulated as random fields. Numerical analyses are performed on tridimensional models of deep excavations in Bogotá soft soils, obtaining system response in terms of damage potential indexes in adjacent buildings. The damage probabilities are assessed for each building and simulated construction stage. Obtained damage probabilities from random field-based modeling are compared with the ones obtained from random-variable based modeling.

C.J. Sainea-Vargas, M.C. Torres-Suárez

Numerical Methods for Simulation of Coupled Hydro-Mechanical Processes in Fractured Porous Media

The contribution is motivated by the need for numerical analysis of flow in fractured porous media, i.e. rocks in the geo-engineering applications. We describe development and testing of numerical methods for simulation of (coupled) flow and deformation in a fractured porous environment. The hydraulic behavior is described by the Darcy flow in the porous matrix and the Poiseuille flow in the fractures. The fractures are considered as domains of reduced dimension. Both the matrix and fracture flow are interconnected by the flux through the fracture walls. The mechanical behavior is described by the linear elastic deformation of the porous matrix with contact conditions on fractures. In this way, it allows fracture opening and closing with the constraint on non-penetration. The slip effects are not considered. We consider both steady-state and time-dependent problems.

Michal Béreš, Radim Blaheta, Simona Domesová, David Horák

Compression Model of Crushable Granular Materials Considering Particle Size Effect

Hydrostatic and one-dimensional compression behavior of granular material are closely related to particle breakage. Tangent constrained modulus may decrease with loading because of the significant crushing of particles. However few compression models could represent this behavior. The traditional semilog linear compression model only shows increasing modulus. In this article, an elasto-plastic compression model is proposed. The plastic strain is divided into plastic hardening strain and plastic breakage strain, the former is due to particle packing, interparticle slip, and rotation, while the latter is due to breakage of asperities and whole-particle fracture. Plastic breakage strain is linked with particle characteristic strength following a power-law particle size effect. The model is verified by experimental results from the literature.

Tianliang Zheng, Erxiang Song

Solving Dynamic Soil Deformation-Fluid Flow Coupling Problems Using Material Point Method

In recent years, there has been an increasing amount of research on the Material Point Method (MPM) for modeling multi-phase coupled problems. Applying MPM in hydro-mechanical problems that interest geotechnical engineers have been explored in many of these studies . The explicit MPM method has been favored in dynamic large deformation problems due to its computational efficiency. However, numerically generated pore pressure oscillation has been a major issue. This paper presents a new formulation of MPM to model coupled soil deformation and pore fluid flow problems. The formulation is presented within the mixture theory framework, and pore water pressure is solved implicitly using a splitting algorithm based on the Chorins projection method. The splitting algorithm helps mitigate numerical instabilities at the incompressibility limit when equal-order interpolation functions are used. It reduces pressure oscillations and a time step size, which is independent of fluid compressibility and soil permeability. The proposed method is validated by comparing the numerical results with the closed form solutions of one dimensional and plane strain problems.

Kenichi Soga, Shyamini Kularathna

Online Geological Anomaly Detection Using Machine Learning in Mechanized Tunneling

In the case of a sudden change in the geology in front of the Tunnel Boring Machine (TBM) during mechanized tunneling processes, non-appropriate investigation and process adaptation may result in non-desirable situations that can induce construction and machine defects. Therefore, subsurface anomalies detection is necessary to trigger alarm to update the process. This paper presents an approach for geological anomaly detection using data produced by the TBM. The data observations are continuously produced at a motion of 10 to 15 s from hundreds of sensors around the TBM. Unsupervised machine learning techniques are applied to analyze the online streaming data. As a result, a model, which is able to learn the system characteristics from normal operational condition and to flag any unanticipated or unexpected behavior, is established. The proposed approach has been tested on the data of the Wehrhahn-Linie metro project in Düsseldorf in Germany. The model can accurately detect the presence of concrete walls in the ground domain with a distance up to around one meter before the TBM approaches the walls. The developed method can thus be used as a monitoring system for ground risks detection to ensure safe and sustainable constructions in mechanized tunneling.

Ba-Trung Cao, Amal Saadallah, Alexey Egorov, Steffen Freitag, Günther Meschke, Katharina Morik

Assessing Transformation Models Using a Geo-Database of Site Investigation Data for the Kathmandu Valley, Nepal

The Seismic Safety and Resilience of Schools in Nepal (SAFER) project has an important aim of producing improved tools for geotechnical and earthquake engineers to assess seismic hazard in the Kathmandu Valley, Nepal. Geo-databases have the potential to offer geotechnical practitioners means to improve a-priori predictions of important soil parameters in geotechnical design. In this paper, some recent work to develop a new database of geotechnical information (SAFER/GEO-591) including shear wave velocity measurements is reported. Attempts to develop new transformation models to better predict shear wave velocity from more basic parameters such as SPT-N values are presented. Use of kriging to better map shear wave velocity for the study area is recommended as a suitable alternative to the presented correlations.

C. E. L. Gilder, P. J. Vardanega, R. M. Pokhrel, R. De Risi, F. De Luca

Plane Strain Failure for Different Constitutive Models

In geotechnical engineering, boundary value problems are often idealized under plane strain conditions. It is therefore of particular interest to investigate constitutive models with respect to plane strain failure. In this contribution, previous studies on elastoplastiticity are linked to the here presented studies on hypoplasticity and barodesy. The parameters of the models are chosen in such way that strength predictions coincide for drained axisymmetric triaxial conditions. The plane strain strength predictions differ due to different failure surfaces and due to different deviatoric directions of stress paths under plane strain conditions. The influence of the initial stress state on peak strength is discussed. As barodesy and hypoplasticity are formulated within the asymptotic state concept, critical stress states are independent of the initial stress state. The results of element test observations are related to a strength reduction analysis.

Gertraud Medicus, Manuel Bode, Franz Tschuchnigg, Barbara Schneider-Muntau

Coupling Continuum Damage Mechanics and Discrete Fracture Models: A Geomechanics Perspective

We present numerical methods to simulate the propagation of discrete fractures embedded in a damaged zone. Continuum Damage Mechanics (CDM) models are implemented in a Finite Element (FE) analysis code. A damage threshold defines the beginning of micro-crack coalescence, when a discrete cohesive segment opens. First, Cohesive Zone (CZ) elements are inserted between volume elements. The length and orientation of the discrete fracture are controlled by the magnitude of the energy released at integration points. The fracture path highly depends on space discretization, but the damage threshold is calculated automatically upon CDM model calibration. Second, an eXtended Finite Element Method (XFEM) approach is proposed. The fracture path is a function of the weighted average direction of maximum damage. Fracture growth depends on a nonlocal internal length, and the damage threshold is set empirically. Both coupling methods perform satisfactorily for simulating pure mode I or pure mode II fracture propagation resulting from micro-crack coalescence. However, the derivation of the Jacobian matrix in the XFEM makes it impractical to couple CDM and CZ models when the damaged stiffness cannot be expressed explicitly. For mixed mode fracture propagation and bifurcation problems, CZ insertion shows great promise, but mesh dependency and computational cost remain challenging.

Chloé F. Arson, Wencheng Jin, Haozhou He

Constitutive Behaviour of Brittle Layered Rocks Using a 3D Anisotropic Hoek and Brown Model

The history of geological deposits is often characterized by complex processes which strongly modify the mechanical behavior of rock masses. The intrinsic orientation-dependent properties connected with the presence of bedding planes induces anisotropic characteristics in the rock masses. In order to model their mechanical behavior, a 3D Hoek & Brown (HB) yield criterion has been used to introduce material symmetries through cross anisotropic elasticity and by means of the Uniaxial Compression Strength (UCS) expressed as a function of the bedding plane inclination. The material degradation and the resulting brittle mechanisms are simulated with a softening rule aimed to introduce a decreasing evolution of the Hoek & Brown parameters, thus enabling to model the post-peak behavior of the intact rock, as well as its non-linear dilation trend. This constitutive framework has been employed to evaluate the influence of preferential directions on the failure process by solving plane strain compression tests in PLAXIS 2D in which a viscous regularization technique is implemented to avoid the pathological mesh-sensitivity of the numerical solution during the formation and propagation of shear bands.

F. Marinelli, N. Zalamea, Giuseppe Cammarata, S. Brasile

A New Constitutive Approach for Simulating Solid- to Fluid-like Phase Transition in Dry and Saturated Granular Media

The authors focus on constitutive modelling of solid to fluid phase transition in granular soils. A new constitutive approach conceived to capture such a transition in either dry or saturated granular material is validated against DEM numerical simulations for steady conditions and discussed in the framework of the μ-e-I rheology. The approach considers granular and liquid phases separately, assuming the two phases work in parallel, as it is according to the effective stress principle in case of quasi-static conditions. The authors emphasize the importance of considering separately the two phase contributions and the limitations of the μ-e-I rheology, in particular in relation to the volumetric response of the material.

Pietro Marveggio, Irene Redaelli, Claudio di Prisco

Simulation of Viscoplastic Material Behavior in Numerical Models

Granular rock salt as a strong time dependent and stress dependent material behavior. For the numerical simulation of this material behavior a new viscoplastic constitutive law was developed and implemented into a Finite-Element-(FE-)Program. The numerical simulation of the material behavior is necessary for the analysis of the stability and the serviceability of large tailings heaps and infrastructure construction in the area around these heaps. The tailings heaps occur during the production of potassium fertilizer and consist of granular rock salt. The paper explains the mathematical formulation of the new viscoplastic constitutive law which is called ViscoSalt 2017 and the implementation into a FE-Program. The salt mechanical material parameters for this constitutive law are determined by load controlled triaxial creep tests and strain rate controlled triaxial fracture tests. For the verification of the new constitutive law and the correct implementation into the FE-Program the back analysis of the triaxial tests is used. Now the new constitutive law is used for the analysis of the stability and the serviceability in engineering practice.

S. Leppla

Estimating Spatial Correlation Statistics from CPT Field Data, Using Convolutional Neural Networks and Random Fields

In site characterization and modelling, subsurface spatial variability is often characterized using the scale of fluctuation, Θ, in the horizontal and vertical directions. Typically, these scales are estimated by statistically fitting an appropriate autocorrelation function to the CPT data from the layer of interest. These statistical techniques are data intensive requiring significant amounts of data to provide accurate estimates. While in the vertical direction, along the CPT, the available data is abundant, the amounts of data in the horizontal plane is limited to the number of CPTs undertaken; therefore, these traditional approaches can adequately estimate vertical scales, Θv, while the horizontal estimate, Θh, is difficult to obtain.This paper aims to expand on the previous work of the Author, in using a neural network-based approach to estimate these spatial statistics from CPT data. This study expands the work from simple 2D domains, modelled as random fields, to 3D, and more realistic site surveys, and the methods are compared.

Jonathan D. Nuttall

Advances in the Study of Micromechanical Behaviour for Granular Materials Using Micro-CT Scanner and 3D Printing

The study of micromechanical behaviour of granular materials has a continuous interest in several engineering fields. Better understanding of the relationship between particle morphology and mechanical performance of such materials is essential in geotechnical applications. Past studies have used discrete element modelling (DEM) to demonstrate the particulate behaviour of granular soils. However, the material properties used as input parameters for DEM simulations are often generalised due to limited data used during calibration and validation exercises. With the advancement of micro-CT scan and 3D printing, improvement can be made to DEM simulations through independent study of particle response for various materials. This paper describes the methodology used to improve DEM simulations and to replicate granular particles by means of 3D printing. Realistic geometric extraction of sand particles was achieved through micro-CT which can then be imported to DEM simulations. To study the influence of particle mineralogy, synthetic particles were produced by means of 3D printing. A range of sintering powders can be used to print particles with various stiffness. The outcomes from the improved DEM models and testing of synthetic printed particles can be used to validate the mechanical behaviour and particle interaction through the independent study of particle morphology, size, angularity, gradation and mineralogy.

M. I. Peerun, Dominic Ek Leong Ong, C. Desha, Erwin Oh, Chung Siung Choo

Constitutive Modelling of the Deformation and Degradation of Railway Ballast Using Multi-laminate Framework

Coarse granular materials such as railway ballast used in the shallow layers of railway tracks are often subjected to moving loads, which cause complex stress conditions involving the rotation of principal stress axes. Further, these materials are involved with particle breakage, which is also affected by the stress changes in the track. Computer modelling incorporating constitutive relationships is an effective technique for assessing the deformation behaviour of coarse granular materials under such conditions. This paper presents a constitutive model for coarse granular materials in multilaminate framework, considering classical plasticity and critical state concepts. A criterion for particle breakage in multi-laminate framework and its effect on the stress-strain behaviour has been incorporated using constitutive relationships in multilaminate framework. The influence of minor principal stress and principal stress rotation on the stress-strain, volumetric strain and particle breakage of these materials have been discussed.

Rakesh S. Malisetty, Buddhima Indraratna, Jayan S. Vinod

Uncertainty and Sensitivity Analysis of Soil Parameters for Tunneling in Urban Area

The excavation and construction of metro structures in a high-density urban area require cautions in the design process. The knowledge of ground should warn the engineers and enable them to take measures to avoid or at least to minimize the potential risks. To achieve that task, numerical simulations are used to determine the deformations due to the construction process. The role played by soil behavior is as fundamental as the values of its parameters. Due to the heterogeneity character of the soil, its random parameters influence on the response of the numerical simulation. A good understanding of that response could be addressed through sensitivity analysis, that is, the assessment of the impact of individual input parameters or sets of input parameters on the response of the model. In this paper, a sensitivity analysis is performed to illustrate the effect of the uncertainty of the input parameters on the response of a numerical simulation of tunnel construction through the finite element code Zsoil. For this purpose, the first-order sensitivity and the total order sensitivity based on Fourier Amplitude Sensitivity (FAST) technics will be performed.

Christian Noubissi, Reza Taherzadeh, Guillaume Puel, Fernando Lopez-Caballero

Quantification of Non-stationary Non-Gaussian Geotechnical Spatial Variability in a Specific Site from Sparse Measurements

Soils and rocks are natural materials, and they are affected by many spatially varying factors during their complex geological formation process. Geotechnical property therefore exhibits spatial variability, which is site-specific. The site-specific spatial variability of geotechnical property is often non-stationary (e.g., with spatial trend) and may not follow a Gaussian distribution. On the other hands, investigation data from a site is often sparse and limited in geotechnical engineering practice due to time and budget constraints. This leads to a great challenge of how to properly quantify the non-stationary and non-Gaussian geotechnical spatial variability in a specific site from sparse measurements. A novel method is presented in this paper to address this challenge. The method is based on Bayesian compressive sampling and Karhunen-Loève expansion, without assumptions of parametric trend function form, parametric auto-correlation function form and marginal probability distribution type.

Yue Hu, Yu Wang

Numerical Investigation of the Strength Variability of Rock Using DEM

Rock failure depends on a high number of variables, one of which is the distribution of defects. To estimate the effect of internal defects on strength variability, numerical simulations of mechanical tests under different loading configurations were run on samples where specific defect distributions were implemented. The Discrete Element Method (DEM) was used to generate three-dimensional rock samples using a bonded particle model. The spheres were joined using cohesive bonds with an interaction radius that allows non contacting spheres within this interaction radius to interact together. To simulate the defect distribution inside rock samples, an internal Weibull distribution of the bond strength was applied. Multiple standard laboratory tests generally used for material characterization were simulated. The Weibull distribution shape parameter of the strength distribution of the samples was then computed. The resulting shape parameters were used to establish a correlation between the shape parameter of the internal strength distribution and the macroscopic shape parameter of the strength distribution.

François Nader, Klaus Thoeni, Anna Giacomini, Stephen Fityus, Olivier Buzzi

Nonlinear Seismic Response of Ground-Structure Systems: Developments and Challenges

Current computational platforms allow unprecedented opportunities for conducting seismic soil-structure interaction simulations. In geomechanics, capabilities such as coupled solid–fluid formulations and incremental-plasticity approaches allow for representation of the involved seismic response. Recent research that facilitated such endeavors in terms of response of ground-foundation-structure systems is presented. Representative numerical results are shown for a number of large-scale soil-structure systems. Graphical user-interfaces for conducting routine three-dimensional (3D) simulations are discussed, as an important element in support of wider adoption and practical implementation. In this context, Performance-Based Earthquake Engineering (PBEE) analysis of bridge-ground systems is highlighted as topical application.

Ahmed Elgamal, Zhijian Qiu, Jinchi Lu, Abdullah Almutairi

Numerical Modelling of Dynamic Compaction of Soils

Dynamic compaction is a process for densifying soils by repeatedly dropping a large tamper from a crane, and this process can be applied to densify a wide range of soils in place to depths greater than ten metres. This procedure has proved to be useful in reducing the potential for settlements associated with wetting of unsaturated soils. Although field experience and experimental tests indicate that compaction efficiency is related to the soil moisture content, the compaction process makes it difficult to install some measurement instruments below the impact areas to study different aspects of the response of unsaturated soils, such as suction and degree of saturation changes. Therefore, numerical modelling could be a more cost-effective way to gain a better understanding of the dynamic response of unsaturated soils and ultimately to improve the efficiency of dynamic compaction on unsaturated soils with different water contents. Due to the numerical difficulties caused by the complexity of constitutive models of unsaturated soils and the dynamic response of a three-phase system, the numerical simulation of dynamic compaction of soils is necessarily limited. In this paper, a finite element model has been developed with an advanced constitutive model implemented, and the generalised-α method has been applied to solve the global equations of motion.

Yue Zhang, Majidreza Nazem, Annan Zhou, John Carter

Effect of Claystone Small-Scale Characteristics on the Variability of Micromechanical Response and on Microcracking Modelling

Argillaceous rocks have a complex and heterogeneous structure at different scales. At the scale of the mineral inclusions embedded in a clay matrix, the deformation generally induces microcracking and material damage. Modelling the latter requires to take into account microscale characteristics and their effect on the micromechanical response. This response can be used in double scale approach to predict material behaviour at larger scale. Thus, heterogeneous microstructures of a claystone are generated with a distribution of morphological properties satisfying experimental observations. The overall microscale material behaviour under solicitation is obtained by numerical homogenisation. Then, the variability of the material response is studied with regard to small-scale characteristics. In terms of deformation and failure, a dominant shear deformation mode and decohesion between grains are observed. The decohesion induces microcracking in the microstructure and strain softening of its overall response.

Benoît Pardoen, Pierre Bésuelle, Stefano Dal Pont, Philippe Cosenza, Jacques Desrues

Reducing Uncertainty in Soil Excavations by Assimilating Direct and Indirect Soil Measurements

Field measurements can be used to improve the estimation of the performance of geotechnical projects (e.g. embankment slopes, soil excavation pits). Previous research has utilised inverse analysis (e.g. the ensemble Kalman filter (EnKF)) to reduce the uncertainty of soil parameters, when measurements are related to the performance, such as inflow, hydraulic head, deformation, etc. In addition, there are also direct measurements, such as CPT measurements, where parameters (i.e. tip resistance and sleeve friction) can be directly correlated with, e.g. soil deformation and/or strength parameters, where conditional simulation via constrained random fields can be used to improve the estimation of the spatial distribution of parameters. This paper combines these two (i.e. direct and indirect) methods together in a soil excavation analysis. The results demonstrate that the parameter uncertainty (and thereby the uncertainty in the response) can be significantly reduced when the two methods are combined.

Cheng Qian, Yajun Li

A Thermodynamics-Based Formulation for Coupled Hydro-Mechanical Behaviour of Unsaturated Soils

The nonlinear behaviour of unsaturated soils is governed by the fully coupled hydro-mechanical phenomenon due to the irrecoverable movement of particles and fluids. It is usually accounted for in constitutive modeling using separate evolution rules for plastic deformation and saturation, linked with two yield conditions for stress and suction. In this paper, a new generic thermodynamics-based approach is developed to provide a more rigorous way to capture these underlying mechanisms. A special form of dissipation potential leading to strong inter-dependence of mechanical and hydraulic internal variables is used for the derivation of a single yield surface. A specific critical state model using a small number of identifiable parameters is derived from the proposed formulation. Its capabilities in predicting the drained and undrained experimental results are investigated to highlight the applicability of our approach.

Dat G. Phan, Giang D. Nguyen, Ha H. Bui, Terry Bennett

An Anisotropic Clay Plasticity Model for the Cyclic Resistance

In this paper, an advanced critical state compatible Bounding Surface (BS) plasticity model for the cyclic response of clays is developed based on a prior version of a Simple Anisotropic CLAY plasticity (SANICLAY) model. With the proposed model, named SANICLAY-BS and abbreviated as S-BS, it is possible to capture the presence of a cyclic stress threshold above which large strains develop leading to the effective stress failure. In addition, the number of cycles to failure can be controlled for a wide range of applied CSRs. Peculiarity of the formulation is the incorporation of a novel activation mechanism into the destructuration law. Model performances in capturing a cyclic resistance curve are shown against the experimental data of Cloverdale clay.

F. Palmieri, M. Taiebat, Yannis F. Dafalias

11th Mercer Lecture on Geosynthetics for Construction on Soft Foundation Soils: An Extended Abstract

This lecture examines the progress made in the last few decades concerning the use of geosynthetics for aiding in the construction on soft soils. Consideration is given to different soft soils ranging from peat to rate-sensitive soft clay and silt. Both relatively elastic and rate-sensitive reinforcements are examined. Consideration is given to basal reinforcement, prefabricated vertical drains, and embankments with reinforcement and other supports such as piles. Particular emphasis is placed on advances since the senior author’s 2002 Giroud lecture.

R. Kerry Rowe, Kaiwen Liu, Daniel King, Louis King

An Image Point Identification Rule for 3D Bounding Surface Plasticity Models

Identification of the correct locations of the current stress and stress reversal points in the 3D stress space is crucial for the successful application of a 3D bounding surface model under complex multiaxial loading conditions. Any miscalculation of the locations of these points can markedly alter the location of the image point on the bounding surface, and consequently affect the model predictions. The main objective of this paper is to present a generalised mapping rule for the identification of image point in 3D bounding surface plasticity models. The mapping rule is based on determination of the exact locations of the stress points in the principal stress space using the eigenvectors of the stress tensors. The mapping rule is implemented in a 3D bounding surface plasticity model to capture the behaviour of soils under multiaxial loading conditions. The simulation results are presented and compared with existing experimental data to validate the proposed model.

H. Moghaddasi, Nasser Khalili, B. Shahbodagh, G. A. Esgandani, A. Khoshghalb

Energy Geoscience and Engineering

Quality of life is strongly correlated with power consumption. The geo-disciplines have a crucial role to play in the energy challenge by contributing solutions to all kind of energy resources from resource recovery to energy and waste storage. Energy geoengineering requires a broad understanding of physical processes (sediments, fractured rocks and complex multiphase fluids), coupled phenomena, constitutive models for extreme conditions, and wide-ranging spatial and time scales. Numerical methods are critical for the analysis, design, and optimal operation of energy geosystems under both short and long-term conditions. Furthermore, they allow “numerical experiments” at temporal and spatial scales that are unattainable in the laboratory. Yet, computer power can provide a false sense of reality and unjustified confidence; simulations face uncertainties related to the validation of complex multi-physics codes, limited data, excessive numbers of degrees of freedom, ill-conditioning, and uncertain model parameters. Dimensional analyses help identify the governing processes and allow for simpler and more reliable simulations. Educational programs must evolve to address the knowledge needs in energy geoscience and engineering.

Juan Carlos Santamarina, Rached Rached

Integrated Modeling of Fully Coupled Two-Phase Surface and Subsurface Flow

An integrated model of fully coupled two-phase surface and subsurface flow was built by using GETFLOWS (GEneral purpose Terrestrial fluid-FLOW Simulator), a finite difference fluid-flow numerical simulator, to perform quantitative evaluation of exchange of overland water and groundwater, subsurface seepage and surface water runoff on the hillside slope surface. Surface water on hillside slope was modeled as open-channel flows and coupled with air-water two phase Darcy flow for underground permeation by using a generalized flow formula. In this study, a simple verification model was firstly built and validated by the extensively used Abdul and Gillham example with simulating the coupled surface and subsurface flow. Then a three-dimensional integrated model of surface and subsurface flow was built by using the DEM (Digital Elevation Model) of a natural mountain slope in Hokkaido, Japan, where runoff induced several debris flows and slope failures occurred during Typhoon 10 hit Hokkaido in 2016. Finally the results of integrated simulation was compared with the results from two-dimensional (2D) impermeable plane flow simulation using Nays2D Flood solver of the iRIC software in the same region. The results suggest that on the hillside slope upstream of embankment, the infiltration rate is equals to the rainfall intensity at the beginning of the rainfall event. After the rainfall intensity is greater than the soil infiltration capacity, runoff is generated. The runoff from upstream allows more water to infiltrate into the embankment causing the possibility of slope failure at the exit of the valley to be much greater than other locations along the highway.

Yulong Zhu, Tatsuya Ishikawa, Srikrishnan Siva Subramanian

Experimental and Numerical Investigation of One-Dimensional Infiltration into Unsaturated Soil

Infiltration characteristics of an unsaturated soil are of interest in both seepage and stability analyses and should be evaluated carefully. In this study, a new large-scale one-dimensional infiltration column test setup was developed, with an inner diameter of 0.24 m and a length of 1.3 m. In the tests conducted, 1.0 m of the column height was filled with soil and 0.3 m remained above for constant water head. The column was instrumented with five pairs of in-situ volumetric water content sensors and suction sensors. This paper explains the methodology used in the construction of the test setup and how the unsaturated properties were calculated for the tested soil, namely the soil water characteristic curve (SWCC) and soil permeability function (SPF). Infiltration tests were performed on a fabricated homogeneous clayey sandy silt similar to naturally available materials representative for Norwegian conditions. Soil specific SWCCs were established under steady state boundary conditions using the sensor outputs, and the results are presented. The instantaneous profile and wetting front advance methods, and relationships based on the SWCC were utilized to establish SPFs, and the results are discussed. A sensitivity analysis was run on the SWCC curve fitting parameters and effects of the parameters on infiltration time are presented. The results from the combined experimental and numerical analysis show that it may be possible to use the new test setup to develop unsaturated soil relationships, but accuracy and measurement range of the sensors are crucial to obtaining consistent results.

Emir Ahmet Oguz, Kate Robinson, Ivan Depina, Vikas Thakur

Hypoplastic Model for Clays with Stiffness Anisotropy

The Intergranular Strain Anisotropy (ISA) model by Fuentes and Triantafyllidis (2015) corresponds to an extension for the conventional hypoplastic models to account for the effects observed under cyclic loading. Similar to the Intergranular Strain (IS) theory proposed by Niemunis and Herle (1997), this extension enhance the hypoplastic models in many aspects as increasing the stiffness and reducing the plastic strain rate on cyclic loading. The present work is devoted to extend and evaluate a constitutive model for anisotropic clays under cyclic loading. The reference model corresponds to the anisotropic hypoplasticity for clays by Mašín (2014), which accounts for an elastic tensor depending on the bedding plane’s orientation. The proposed model results from extending the hypoplastic model with ISA. For validation purposes, different simulations under monotonic and cyclic loading were performed with an anisotropic kaolin clay. It was found that the proposed model accurately predict the experimental results under a wide range of strain amplitudes.

Jose Duque, David Mašín, William Fuentes

Efficient Implementation of the Bayesian Inversion by MCMC with Acceleration of Posterior Sampling Using Surrogate Models

The contribution is motivated by the Bayesian approach to the solution of material identification problems which frequently appear in geo-engineering. We shall consider the cases with associated forward model describing flow in porous media with or without fractures as well as coupled hydro-mechanical processes. When assuming uncertainties in observed data, the use of the Bayesian inversion is natural. In comparison to deterministic methods, which lead only to a point estimate of the identified parameters, the Bayesian approach provides their probability distribution. The implementation of the Bayesian inversion is realized via Markov Chain Monte Carlo methods. The paper aims at the acceleration of the posterior sampling using a surrogate model that provides a polynomial approximation of the full forward model. The sampling procedure is based on the delayed acceptance Metropolis-Hastings (DAMH) algorithm. Therefore, for each proposed sample, the acceptance decision contains a preliminary step, which works only with an approximated posterior distribution constructed using the surrogate model. Furthermore, the approximated posterior distribution is being updated using new snapshots obtained during the sampling process. The posterior distribution updates are realized via updates of the surrogate model. The application of the described approach is shown through several model examples including flow in porous media with fractures and hydro-mechanical coupling.

Simona Domesová, Michal Béreš, Radim Blaheta

Development of Cellular Automata Software for Engineering Rockmass Fracturing Processes

This paper presents the development of self-developed cellular automata software for engineering rockmass fracturing processes (CASRock). CASRock is a combination of cellular automaton, rock mechanics, engineering geology, elasto-plastic mechanics and fracture mechanics. CASRock was initially developed to simulate the failure process of heterogeneous rock, and it is improved to focus on the fracturing process of engineering rockmass. The use of a cellular automaton allows CASRock to accurately represent the real fracturing characteristics of engineering rockmass. This process is a ‘down-top’ way handle the fracturing behaviour of rockmass. CASRock contains several mechanical models, including the 3D elastic-plastic-ductile-brittle model, for different applications in rockmass engineering. New stability analysis indexes, e.g., the RFD (rock fracturing degree), are incorporated into CASRock to evaluate the fracturing degree of engineering rockmass. A parallel cellular automaton updating rule is developed for large-scale stability analysis of engineering rockmass. The theory and software functions are briefly introduced. Several applications are presented to show the ability of CASRock to simulate engineering rockmass failure processes under complex conditions.

Xia-Ting Feng, Peng-Zhi Pan, Zhaofeng Wang, Youliang Zhang

A Generalized Constitutive Relationship for Undrained Soil Structure Interaction Problems

The macroelement approach, commonly employed to study soil-structure interaction problems, stems from the intent of describing the mechanical response of a complex system by means of a single upscaled constitutive relationship, relating generalized stresses and strains.In this paper, the authors introduce a new generalized constitutive relationship capable of reproducing the undrained mechanical response of both foundations and tunnel cavities. To this aim, the authors performed a series of numerical analyses. The numerical analyses results are interpreted to put in evidence that the mechanical response of both systems is governed by a “structural hardening” associated with the spatial propagation of the yielded soil domain that is influenced by the relative position of the structure with respect ground surface: when the yielded soil domain reaches the ground surface a failure condition is got. To take into account this aspect, the authors introduced in the constitutive relationship two independent plastic mechanisms, the former one defines the spatial propagation of the yielded soil domain (structural hardening), whereas the latter one the failure mechanism due to the boundary condition. The comparison of the constitutive relationship predictions with the finite element numerical data demonstrates that the proposed model is capable at the same time of satisfactorily reproducing the mechanical response of shallow/deep tunnels and shallow/embedded foundations.

Claudio di Prisco, Luca Flessati

Development of a Robust Coupled Material Point Method

The material point method (MPM) shows promise for the simulation of large deformations in history-dependent materials such as soils. However, in general, it suffers from oscillations and inaccuracies due to its use of numerical integration and stress recovery at non-ideal locations. The development of a hydro-mechanical model, which does not suffer from oscillations is presented, including a number of benchmarks which prove its accuracy, robustness and numerical convergence. In this study, particular attention has been paid to the formulation of two-phase coupled material point method and the mitigation of volumetric locking caused numerical instability when using low-order finite elements for (nearly) incompressible problems. The numerical results show that the generalized interpolation material point (GIMP) method with selective reduced integration (SRI), patch recovery and composite material point method (CMPM) (named as GC-SRI-patch) is able to capture key processes such as pore pressure build-up and consolidation.

Xiangcou Zheng, José L. González Acosta, Guido Remmerswaal, Philip J. Vardon, Federico Pisanò, Michael A. Hicks

Numerical Modelling of Soil-Pile Interface Response

Many Offshore wind projects are being developed nowadays. Design of monopiles, the most used foundation system for the offshore wind turbines, requires a special attention in the characterization of the soil-pile interaction. The main feature induced by axial cyclic loading at the level of soil-pile interface is the decrease in normal stress. Hence, evolution of soil-pile interface normal stress may affect shearing mechanism of the pile. Using a finite difference software, this paper presents an alternative method to simulate the interface response. Curves illustrating the evolution of normal displacement in function of shear displacement, extracted from experimental shear tests, were directly injected as disturbed relative normal displacement in the interface nodes. Therefore, shear stresses of the interface nodes are directly corrected by equilibrium procedure, based on the principle of elasto-plasticity. Calculation results present good agreement with experimental results.

M. Doghman, Hussein Mroueh, Sebastien Burlon

Bayesian Uncertainty Quantification for Geomechanical Models at Micro and Macro Scales

Uncertainty exists in geomaterials at contact, microstructural, and continuum scales. To develop predictive, robust multi-scale models for geotechnical problems, the new challenge is to allow for the propagation of model/parameter uncertainty (conditioned on laboratory/field measurements) between micro and macro scales. We aim to first quantify these uncertainties using an iterative Bayesian filtering framework. The framework utilizes the recursive Bayes’ rule to quantify the evolution of parameter uncertainties over time, and the nonparametric Gaussian mixture model to iteratively resample parameter space. Using the iteratively trained mixture to guide resampling, model evaluations are allocated asymptotically close to posterior modes, thus greatly reducing the computation cost. In this paper, we first respectively quantify the parameter uncertainty of models that are discrete and continuum in nature, namely a discrete particle and an elasto-plastic model. We then link the two models by conditioning their uncertainties on the same stress-strain response, thereby revealing micro-macro parameter correlations and their uncertainties. The micro-macro correlations obtained can be either general for any granular materials that share similar polydispersity or conditioned on the laboratory data of specific ones.

Hongyang Cheng, Vanessa Magnanimo, Takayuki Shuku, Stefan Luding, Thomas Weinhart

Evolving Elastic and Plastic Fabric Anisotropy in Granular Materials: Theoretical and Applied Implications

In this paper a relationship between elastic anisotropy, as typically observed in clayey soils subjected to shear wave propagation tests, and plastic anisotropy, detected at yielding and leading to rotated yield loci, is proposed. Furthermore, elastic and plastic anisotropies exhibit an evolving character, as a consequence of the evolution of the fabric of the material induced, for example, by irreversible straining. First, the theoretical implications of the above evolving character of fabric, which leads to a new form of anisotropic elasto-plastic coupling, are investigated. Then, a strategy is proposed to take advantage of such a coupling to more effectively initialise the internal variables of any non-isotropic hardening plasticity model. This latter aspect is of crucial importance when numerically analysing the response of a whole deposit of soil, as for each sub-stratum it is mandatory to identify the initial orientation of the yield locus.

Angelo Amorosi, Fabio Rollo, Yannis F. Dafalias

Geogenic Arsenic Release by Iron-Oxides Reductive Dissolution in Aquifer Systems

We focus on modeling geogenic arsenic mobilization induced by Fe-oxides reductive dissolution and aim at a preliminary assessment of the potential of such a mechanism to release arsenic under conditions that are typically found in alluvial aquifers. Under reducing conditions, Fe-oxides might be dissolved by iron-reducing bacteria, thus leading to simultaneous release of arsenic which is then typically absorbed and co-precipitated on Fe-oxides. We leverage on a kinetic model to describe this mechanism and resort to a global sensitivity analysis framework to explore the way the concentration of arsenic resulting from sediment-water interaction in a batch system is influenced by (i) available initial mass (per mass of sediments) of Fe-oxides, (ii) amount of arsenic initially adsorbed on Fe-oxides, and (iii) concentration of dissolved organic carbon for bacterial metabolism. Our analyses are conducive to (i) a preliminary assessment of the relative importance of multiple factors on the release of arsenic to groundwater by iron-oxides reductive dissolution and (ii) useful indications to improve the proposed geochemical model and its future transferability to flowing systems.

Giulia Ceriotti, Alberto Guadagnini

Application of Intelligent Compaction (IC) as a Quality Control Tool: An Oklahoma Experience

Performance of asphalt pavements depends on the quality of compaction achieved during construction. Asphalt cores as an indicator of construction quality are not reliable because they typically cover less than 1% of the constructed pavement. Intelligent compaction (IC) estimates the level of compaction of the entire pavement layer during construction. IC rollers are equipped with accelerometers for measuring vibration, a GPS for monitoring spatial location, a temperature sensor for measuring surface temperature and an on-board computer for real-time execution of software and data storage. Although IC shows great promise as a quality control tool, there are concerns regarding the quality and analysis of data including missing data, data accuracy, data filtering, and data interpretation. Also, verifying compliance of the IC output with Department of Transportation (DOT) requirements needs accurate project boundaries. Project boundaries obtained from the onboard GPS may not be adequate for verifying compliance. In this study, the IC data from three pilot projects in Oklahoma were analyzed using the VETA (v 5.1) software, which is a map-based tool for viewing and analyzing IC data. Three different IC providers were used in collecting these IC data. A high degree of variability in collected data was observed, including inconsistent file naming, unspecified target for number of roller passes and inadequate layout of project boundaries. Despite variability, coverage, number of roller pass, compaction temperature, roller speed and roller frequency were found useful as indicators of compaction quality. Project size and operator training were also found to be important factors for successful implementation of intelligent compaction as a quality control tool.

Mohammad Ashiqur Rahman, Musharraf Zaman, Blake Gerard, Jason Shawn, Syed Ashik Ali, Kenneth R. Hobson

Modelling the Stress-Strain Behaviour of a Soft Soil Improved with an Environmentally Friendly Binder

The paper focuses on the numerical prediction of the stress-strain behaviour under triaxial compression of a sandy clay soil improved with an environmentally friendly binder at the short-term (28 days) and long-term (90 days) using a kinematic hardening constitutive model. The binder was synthesised by ground granulated blast furnace slag (GGBS), an industrial by-product (IBP) of the steel industry, and sodium hydroxide (NaOH). The model, which is being used to reproduce artificially cemented soil behaviour for the first time, was able to successfully capture the smooth elastic-plastic transition response in the unimproved soil, while a ductile response observed in the improved soil prior to a fragile post-peak and residual states was also well predicted by the model.

Manuela Corrêa-Silva, Mohamed Rouainia, Tiago Miranda, Nuno Cristelo

Evolution of Undrained Strength Under a Test Embankment

Increased traffic and environmental loads necessitate re-evaluation of the stability of existing road and railway embankments built on soft sensitive clays. Thus, the current mobilised undrained shear strength needs to be quantified. A methodology to evaluate changes in undrained shear strength under embankment loading is developed and applied for the case of Haarajoki test embankment. The methodology combines boundary value modelling of embankment loading with integration point level stress path probing using the Creep-SCLAY1S model. The changes in the stress state and the relevant state parameters resulting from the boundary value modelling enable the quantification of the mobilised undrained shear strength. The results indicate an increase in the undrained shear strength up to 17% in the most affected clay layer. The high pre-overburden pressure in the top of clay deposit prevents significant changes in the undrained shear strength in the case of Haarajoki. Thus, when assessing changes in the undrained shear strength, one of main parameters to determine is the initial preconsolidation pressure.

Hannes Hernvall, Mats Karlsson, Jelke Dijkstra, Minna Karstunen

Modelling Failure in Layered Geological Formations - FDEM: A Micro-mechanical Approach that Bridges Across Scales

The hybrid finite/discrete element method (FDEM) is an innovative numerical technology that combines the advantages of large-strain finite elements with those of discrete elements, allowing for explicit modelling of the propagation of cracks in heterogeneous brittle rocks, as well as the interaction between their different constituent phases and materials. By modelling these physical interactions at the micro-scale, FDEM is able to reproduce the responses of excavation in layered and bedded rock at multiple scales as an emergent property of the model. Following an overview of the FDEM basic principles, failure process observed in shale rock will be presented and discussed within the manuscript.

Aly Abdelaziz, Giovanni Grasselli

Investigation of Uncertainty in Strength Parameter Identification

Geotechnical parameters scatter in a wide range. On the one hand, this is due to the spatial variability of the subsoil, but also results of laboratory tests on reconstituted specimens of one sample scatter, as a completely homogeneous, reproducible specimen preparation is not feasible. For calculations according to the standards, characteristic shear parameters should be chosen as cautious estimate of the mean values. How this cautious estimate should be determined is not defined and therefore subjective. Often the results of shear tests are used as basis for the decision. In this paper, results of drained triaxial compression tests on a reconstituted, natural, widely graded soil are investigated. The specimens were prepared at same mean density but the results of the shear experiments scatter. The deviation of e.g. the peak strength is apparent. For the derivation of the Mohr-Coulomb parameter friction angle and cohesion according to the standards 3 or more stress levels have to be considered. The influence of the number of stress levels taken for the evaluation of the shear strength parameters is quantified. The evaluation of only three stress levels leads to a relatively large range of possible shear parameters. The two shear parameters friction angle and cohesion are statistically dependent - since they are two parameters of a linear regression. Therefore, they should be considered together. The scattering in the peak strength is probably caused by an inhomogeneous specimen construction. The influence of an inhomogeneous specimen preparation on the peak strength is investigated and proven in numerical simulations.

Barbara Schneider-Muntau, Gertraud Medicus, Jacques Desrues, E. Andò, Gioacchino Viggiani

Liquefaction as Microstructural Instability and Validations: The Disturbed State Concept

Instabilities can occur in solids and fluid infiltrated granular systems affected by elastic, plastic and creep strains, friction, adhesion, sliding, rotation of grains/particles and surface forces due to readjustment or reorganization of the microstructure. Instabilities can occur at multiple locations at different states during deformation, e.g. transition from compactive to dilative volume change, peak condition and critical states at which failure or liquefaction initiates leading to final liquefaction. Conventionally, liquefaction is often identified based on the comparison of induced pore water pressure and the initial effective stress, which is considered to be an external method to represent the internal mechanism in the deforming material, which may not be realistic. In contrast, the disturbed state concept (DSC) and energy approaches can provide fundamental procedures and allow for internal mechanisms. The DSC provides a unique and basic model for the initiation and final liquefactions corresponding to the critical (Dc) and final (Df) disturbances, respectively. The issue like shear band formation occurs as a special case and can represent only one state of such distributed mechanisms. The DSC for liquefaction analysis is emphasized in this paper. A number of laboratories simulated and field validations for geomechanical problems are also presented.

Chandrakant S. Desai, Mohamad Essa Alyounis

Discrete Numerical Modelling of a Cohesive Soil Layer Reinforced by Geosynthetic Sheet Using an Advanced Constitutive Law

The occurrence of a sinkhole in an area may compromise the safety of the existing structures and infrastructures. Therefore preventive solutions are necessary. Recently, a coupled DEM-FEM numerical model has been developed to better account for the failure mode of reinforced soil layers during cavity openings and the interaction between the collapsed soil and the geosynthetic sheet. An experimental campaign on a small scale trapdoor model gave the possibility to validate the numerical model. In that case, a usual linear elasto - perfectly plastic Mohr Coulomb constitutive law and its failure criterion have been chosen to represent the cohesive soil. A good agreement with the experimental results has been observed. To be able to reproduce the behavior of various cohesive materials, an advanced constitutive law has been tested in place of the usual model based on the Mohr Coulomb criterion.

Maria Delli Carpini, Pascal Villard, Fabrice Emeriault

Back-Calculation of Stresses and Pore Pressures Around a Penetrating Cone in Silt

Interpretation of CPTU in silts is challenging compared to sands or clays since penetration occurs allowing partial drainage. Further insight into the soil response around a penetrating cone in silts is needed, including volumetric changes and pore pressures. This paper presents measured cone resistance, soil stress and pore pressure in silt during model scale penetration tests with penetration velocities varied by three orders of magnitude. The experimental results are back-calculated by finite element simulations to identify key aspects of the silt behavior during penetration of the cone.

Priscilla Paniagua, Steinar Nordal, Arnfinn Emdal, Harun K. Engin, Yunhee Kim

Measurement and Study of Steel Pipe Jacking Force in Silty Sand Stratum

There are several well-established jacking force empirical models available for predicting the jacking force. However, the jacking force calculated by different empirical formulas have big difference and the face resistance is difficult to measure directly. These factors constrain the prediction of the jacking force in design stage. This paper introduces a pipe jacking technology with non-over excavation. The data of jacking force and steel pipe stress were recorded and analyzed in the process of pipe jacking. According to field monitoring data and the finite element numerical simulation results, the face resistance and the friction resistance can be obtained by back analysis. And the face resistance obtained is compared with the empirical value. The results show that JMTA and P-K models have practical significance in calculating face resistance F0, while Ma Baosong model underestimates the value of face resistance in silty sand formation. This research can provide a theoretical basis for the selection of jacking force prediction model.

Lian-Jin Tao, Yu Zhang, Xu Zhao

Application of an HMC Based Approximate Method for Combined Identification of Hydraulic Conductivity and Piping Region Interface

The detection of piping and the extent to which it progresses is important in the serviceability of natural dams and levees, where the soil is usually poorly consolidated and filters or drainage zones are absent. Practically, information of the spatial variation of hydraulic conductivity is also unavailable in the domain of interest. An approximate version of a Hamiltonian Monte Carlo (HMC) based method for combined probabilistic inversion is detailed. The inverse problem consists of Karhunen-Loève (KL) expansion parameters and solid-void interface parameters which are determined simultaneously. The interface parameter updates are carried out using a reversible proposal in a mesh moving framework. To maintain computational efficiency, the parameter update is enforced in an approximate sense, where the covariance matrix for the KL expansion is kept constant throughout the analysis. Synthetic data from a numerical experiment on a domain containing a predefined piping region, is used to validate the approximate method. A total of 30000 samples are generated using the HMC sampler. Results show that the Markov chains converge to the stationary distribution. A good match is also observed between the inferred mean interface, and the true interface and the true spatial distribution of hydraulic conductivity is obtained.

Michael C. Koch, Misato Osugi, Kazunori Fujisawa, Akira Murakami

The Strength Reduction Method in Clay Hypoplasticity

An evaluation of the slope stability in FEM software is often performed as a complementary analysis to the plastic deformation analysis. The slope stability represented by the factor of safety is, in the most of FEM software, evaluated by the reduction of the strength parameters $$c$$ c and $$\varphi $$ φ of the Mohr-Coulomb model. Consequently, the lack of the strength reduction method for the advanced constitutive models inevitably leads to its substitution by the Mohr-Coulomb model and necessity of a further recalibration of the constitutive model parameters. Therefore, new method of the strength reduction was developed for the Masin’s hypoplastic model for clays. A subsequent return of a deviatoric stress to the asymptotic state boundary surface is implemented in this method so that all the integration points within the FEM remain within asymptotic state boundary surface. Predictions of the newly developed method is thoroughly testes from the quantitative as well as qualitative point of view and eventually compared with the predictions of the Mohr-Coulomb model.

T. Kadlicek, David Mašín

Integration of Data Assimilation Techniques in Geomechanical Modelling: Ensemble Smoother with Multiple Data Assimilation Analysis

The use of Data Assimilation (DA) techniques is receiving an increasing interest in geomechanical applications, with the aim to assess and reduce uncertainties associated to numerical outcomes by model constrain with available measurements. In geomechanical simulations, ensemble-based DA approaches are usually preferred. Among such techniques, Ensemble Smoother with Multiple Data Assimilation (MDA-ES) is usually recognized to improve the outcomes in nonlinear problems, but its use and parameter definition is still object of research. In this paper, MDA-ES has been tested in a synthetic case study dealing with the prediction of land subsidence above a producing hydrocarbon reservoir. Its effectiveness has been investigated varying both the DA parametrization and the geomechanical properties.

Laura Gazzola, Massimiliano Ferronato, Matteo Frigo, Pietro Teatini, Claudia Zoccarato

Prediction of Strength-Band of Methane Hydrate-Bearing Sand by Elastoplastic Constitutive Model Considering Microstructure of Gas Hydrates

In the present study, we propose a new elastoplastic constitutive equation with consideration of the hydrate morphology. Then, using the proposed constitutive equation, we investigate how large the strength and the volumetric strain change by the change in the hydrate morphology with the fixed total hydrate saturation. The result indicates that the strength and the positive dilatancy becomes the larger in the case where the morphology of the cementing-type is more dominant. Moreover, the strength curves predicted by the proposed model is in good agreement with the past experimental research. This makes it possible to predict the strength and the deformation behavior of MH-bearing sediments even in the area where there is a lack of research data.

Hiromasa Iwai, Takaya Kawasaki, Ho Cho

Prediction of Frictional Jacking Forces Using Bayesian Inference

Application of pipe-jacking method in the form of microtunneling has become more popular over the conventional open cut method for the installation of underground infrastructure such as buried sewer pipelines in urban setting in recent years. This is due to the advantages offered by trenchless technology such as reduced disruptions to traffic and the surrounding environment as well as minimized ground settlements. Prediction of frictional jacking forces is a crucial component of the design of pipe-jacking works. In view of the challenges faced in calculating pipe-jacking forces in highly weathered and highly fractured geological formations, this paper proposes the use of Bayesian inference method to predict the frictional jacking forces developed from traversing the weathered rock formations. A probabilistic framework based on Bayesian approach is proposed using a well-established pipe-jacking force model, which considers arching effect from the surrounding ground. The main advantages of Bayesian inference include (i) consideration of uncertainty in deriving the soil parameters and (ii) ability to incorporate prior information and expert judgement from previous research studies into the model in the form of prior distribution. The model uncertainty is expected to be significantly reduced through the sequential updating process when more data become available.

Siaw Chian Jong, Dominic Ek Leong Ong, Erwin Oh, Chung Siung Choo

Measuring and Modelling Cyclic Response of Dense Sand Under Partially Drained Conditions

Cyclic laboratory tests on sand are generally performed either under drained or undrained conditions, while the actual in-situ conditions typically are partially drained. It is therefore necessary to make some assumptions in order to use the cyclic properties obtained from these tests in design. To check the consequence of these assumptions some special cyclic triaxial tests with different degree of drainage are therefore carried out at NGI. This paper presents the results from these tests together with a detailed interpretation. It is shown that the measured accumulated pore pressure and volumetric strain may be very well back-calculated by three basic equations. The accumulated volumetric strain during a cycle is the key material property, together with a represented bulk modulus and the flow resistance of the special filter device. Based on the results, it is concluded that more study is required to fully understand the governing properties that controls the accumulated strains, especially the effect of previous stress or strain history.

Hans Petter Jostad, Pasquale Carotenuto, Suzuki Yusuke, Nallathamby Sivasithamparam

A Discrete Fracture Network Approach to Rock Mass Classification

In contrast to many disciplines, the approach to design in rock engineering remains largely inductive: observations, experience and engineering judgment are used to infer the behavior of a problem that cannot be constrained due to the nature of geological/geotechnical materials. Most of the rock mass classification systems used for rock engineering design purposes were developed in the 1960s and 1970s; since then no major updates have been proposed to reflect modern data collection tools and modelling procedures. Furthermore, engineers have attempted to apply existing classification systems in the context of a probabilistic design approach despite most of those systems being based on qualitative and semi-quantitative measurements. In this paper, we use a discrete fracture network (DFN) approach to introduce the first component of a new quantitative classification system that can capture rock mass scale, anisotropic effects; and better reflects the degree of connectivity of the natural fracture network. A new network connectivity index (NCI) is introduced that uses areal fracture intensity and density, and intersection density to provide a quantitative description of rock mass blockiness.

Davide Elmo, B. Yang, Dean Stead, S. Rogers

Effects of Contamination and Dry Density on Dielectric Properties of Soils with Different Specific Surface Area

Dielectric properties of soils are of paramount significant in geo-environmental applications. Despite the well-studied effects of water content on the soil dielectric permittivity, the simultaneous effects of wet contamination and dry density have remained relatively untapped. This paper investigates these effects on three soils (silica sand, kaolinite and bentonite) with distinct specific surface area at 1 GHz. The results of the experimental program were evaluated against the Birchak model. It was found that the relationship between dry density and dielectric properties is directly proportional for soil/oil mixtures. Furthermore, the geometrical parameter in the Birchak model was found to be relatively constant for soil/oil mixtures, presumably due to the non-polar molecular structure of the contaminant under study (i.e., oil). For soil-water mixtures, however, it is suggested that this parameter is a non-constant value and is a function of dry density.

Hao Yu, Amir Orangi, Fangyuan Lin, Guillermo A. Narsilio

On the Numerical Implementation of a Thermomechanical Hyperplasticity Model for Fine-Grained Soils

The numerical implementation of a recently developed thermomechanical constitutive model for fine-grained soils based on hyperelasticity-hyperplasticity theory (Golchin et al. 2020), is presented. A new unconventional implicit stress return mapping algorithm, compatible with elasticity derived from Gibbs (complementary) energy potential, in strain invariant space, is designed and the consistent tangent operator for use in boundary value problems (such as in the finite element method) is derived. It is shown that the rate of convergence of the stress integration algorithm is quadratic. The numerical results are in good agreement with available data from thermomechanical element tests found in literature.

A. Golchin, Philip J. Vardon, Michael A. Hicks, William M. Coombs, I.A. Pantev

Validation of Numerical Analysis for Deformation of Clay Ground Based on Uncertainty Quantification

A numerical analysis was validated for shear and consolidation deformation of clay ground base on uncertainty quantification referring ASME V&V10.1 (2012). The numerical analysis is a soil-water coupled analysis on finite deformation porous media theory. First, centrifugal experiments with the established conditions were performed, and probability distributions of deformation of clay ground were obtained. Second, some triaxial tests with the established conditions were performed, and some elasto-plastic material parameters were assumed as normal distributions from the test results. Third, numerical analyses simulated the centrifugal experiments of clay ground deformation using the uncertainty of elasto-plastic parameters and the embankment load. By comparing the experimental and numerical results, the uncertainty quantification of clay ground deformation and validity of numerical method were discussed. The area matric MSRQ was used to assess the validity. In this example, MSRQ of vertical displacement at the embankment toe was quite large due to the biased distribution of numerical solutions.

Daiki Hizen, Ryosuke Uzuoka, Katsutoshi Ueno

A Visco-Elastic DEM Model of Rock Under Different Loading Rates

A numerical model based on two-dimensional Discrete Element Method (DEM) has been used to study the compression of rock under different loading rates, and a visco-elastic Flat-Joint constitutive law has been developed to describe the dynamic behavior of bonded contact between particles. The improved DEM model consists of two parts: (1) Force-displacement equations are derived on the basis of a visco-elastic constitutive model which is formed with a spring and a Maxwell system, and (2) A dynamic fracture criterion of bond is develop to define the increase of strength. The controlling variable method is used to analyze the impact of visco-elastic parameters on the dynamic mechanical properties. With different parameters this model could be used to simulate the compression of rock materials under different loading rates. As an example, visco-elastic parameters of granite are identified, and the obtained stress-strain curves well reproduce the laboratory results.

Xun He, Yong He, Xuchao Pan, Lei Guo, Zhong Fang, Hong Chen, Jie Shen

Numerical Investigation on the Effect of Grain Crushing Process on Critical State on Rockfill Material

To explore the difference between the critical state lines (CSL) of crushable and uncrushable sand with the same gradation as crushable sand at the critical state, two sets of DEM simulations are conducted with different confining pressure. A series of Large-scale triaxial compression test were carried out on rockfill material as the basis for calibration of discrete element model parameters. At first, a crushable rockfill sample was sheared to reach critical state. After that, the sample with the critical state gradation of first set was recovered to isotropic consolidation state with the same confining pressure and sheared to critical state under the same stress path. A crushable DEM sand sample was established with validated particle failure criterion and fragment replacement method. The DEM model of first sets were validated and calibrate by experiment results by the stress-strain behavior. And the breakage extent of DEM model was also investigated. The same parameters were used in the rest simulations. The stress-strain behavior of uncrushable sample and CSL of both samples were obtained. From the results, the important influence of the process of the grain crushing on the CSL location was observed although this two set of simulations have the same final PSD.

Lei Wang, Minqiang Meng, Hanlong Liu, Yang Xiao

Experimental and DEM Study of Two Dimensional Simple Shear

It is well established that the principal stress rotation (PSR) can lead to plastic deformations in soil, and soil is subjected to two dimensional shears in many geotechnical applications, which lead to two dimensional principal stress rotations. This paper aims to study impacts of two dimensional PSRs on soil behavior by using the DEM and experimentation, in which glass beads are used. In the two directional simple shear apparatus, the first shear is exerted on samples along one direction, followed by the second shear at varying angles to the first shear. The experimental results indicate that the angle between the first and second shears have a great impact on the sample strength. The DEM results are in very good agreement with the experimental results on the development of both shear stress and volumetric change. Further, lateral normal stresses in the simple shear in the DEM study can be obtained, enabling the computation of principal stresses under two dimensional shears. Fabric developments of samples can also be studied in the DEM simulation.

Yunming Yang, Min Zhang, Hanwen Zhang, Hai-Sui Yu

Numerical Modelling of Thermo-active Micropiles

Energy piles (EPs), consisting in piled foundations equipped with heat exchangers, have been extensively studied in recent years, both from the thermo-mechanical response and energy performance points of view. However, most research refers to typical rotary bored, CFA or precast driven, medium diameter piles. Not much attention has been devoted to so-called energy micropiles (EMPs), representing an opportunity to provide at the same time energy and structural retrofitting to existing buildings. Existing studies show that EMPs overall may thermally perform differently to EPs, but they are comparable in terms of specific heat flux. In this work, a 3D FE numerical model is employed to perform a comprehensive parametric study considering design factors that are peculiar to EMPs, to assess the most important parameters to maximize their energy performance. The parameter space is efficiently explored resorting to a statistically-based Taguchi approach. Results show that thermal design of EMPs should not be based on the same criteria as those used for medium-large diameter EPs, since different parameters are dominant in enhancing their energy performance. In particular, the pipes diameter should be maximized in EMPs for its strong influence in results, while being very easy to engineer.

Diana Salciarini, Francesco Cecinato

High-Resolution Modelling of Axisymmetric Granular Column Collapse Using Parallelized SPH

Granular flows are relevant to a variety of engineering applications from risk management of natural phenomena such as landslides and rock avalanches, to flow of pills in the pharmaceutical industry. The granular column collapse is an important experiment to study because of the exhibition of both solid and fluid-like behaviours of granular material. Here we present the continuum simulation of axisymmetric granular column collapse for aspect ratios up to 30 by using two constitutive relations: an elasto-plastic model with Drucker-Prager yield criterion, and the $$\mu \left(I\right)$$ μ I rheological model for dense granular flows. Both models are implemented into a Smoothed Particle Hydrodynamics (SPH) code parallelised for CPU clusters with thousands of cores. While very good agreement with experimental data has been reported for both models for small and intermediate aspect ratios, the large-scale simulations conducted for large aspect ratios show that the Drucker-Prager model tends to over-predict final deposit height, and the (I) model under-predicts it. The differences in flow behaviour and final deposit morphology appear to be largely due to the different volumetric behaviour of the models, as well as the rate independence of the elasto-plastic approach whereas the $$\mu \left(I\right)$$ μ I model is rate dependent.

Edward Yang, Ha H. Bui, Giang D. Nguyen, Abdelmalek Bouazza, Hans De Sterck

Effect of Domain Size in the Modelled Response of Thermally-Activated Piles

The application of thermally-activated pile foundations has received significant attention in the last decade with a number of large- and small-scale tests having been undertaken. Alongside these physical studies, a number of investigations utilising numerical analysis have been undertaken to examine the behaviour of single piles and pile groups. Focussing on studies examining single piles, it is apparent that a variety of differing domain dimensions have been used. The work presented in this paper had the objective of systematically examining the influence of the domain size and how it affects the predicted thermo-mechanical response of the pile. It shows that the domain size has an important impact on the initial distribution of mobilised shaft friction due to applied mechanical load which then impacts on the subsequent thermo-mechanical response.

Martina Zito, Teresa Maria Bodas Freitas, Peter J. Bourne-Webb, Donatella Sterpi

Numerical Modeling of Water-Vapor Migration and Phase Transformation in Unsaturated Freezing Soils

Because of ignoring the vapor migration in freezing soils, coarse-grained soils have long been deemed not susceptible to frost heave. However, recent studies reveal that vapor migration can increase the total water content and lead to remarkable frost heave hazards in coarse-grained soils. In this paper, a new numerical model is developed based on the coupled thermal and hydrological processes. The soil water characteristic curve and the soil freezing characteristic curve are taken into account in this model. The model is established by using COMSOL Multiphysics which contains 5 equations and 5 variables. In order to validate the numerical model, laboratory experiments were performed in coarse-grained soils. The result shows that there are sharp increases in water content at the top of samples and the freezing front. A good match between measured and computed results indicates that the new model can make a good explanation for the coupled movement of heat and moisture in coarse-grained soils.

Feng Shan, Jidong Teng, Xiaodong Yan, Sheng Zhang, Daichao Sheng

Simulation of Cavity Expansion with the Clay and Sand Model Using G-PFEM

The well-established cavity expansion theory has already been applied to numerous practical problems in geotechnical engineering. Analytical solutions taking into account advanced constitutive soil models, such as the available solutions for drained and undrained cavity expansion using the unified state parameter model for clay and sand (CASM), represent also valuable reference solutions for the validation of numerical models. In this work, the code G-PFEM is used for the fully-coupled analysis of cavity expansion problems at large strains, in order to validate the performance of the numerical model with the implemented CASM under drained and undrained conditions and to investigate cavity expansion under the influence of partial drainage. It is shown that the numerical results compare well with the analytical solutions. Furthermore, the effect of partial drainage where consolidation takes place during the cavity expansion process is highlighted.

Laurin Hauser, Helmut F. Schweiger

The Evaluation of the Suitability of Ryukyu Limestone as Foundations of Large Engineering Structures

Ryukyu limestone formation is considered to be not suitable as a foundation rock for large-scale engineering structures in Okinawa Prefecture. However, when Ryukyu limestone formation is quite thick, it results in non-economical foundation design. The characteristics of Ryukyu limestone with various porosity under static and dynamic conditions are investigated and shear behaviour the interface between piles and Ryukyu limestone are tested using large-scale dynamic shear testing device. Furthermore, some photo-elasticity tests on model piles founded model grounds with and without cavities were subjected to loads to check their deformation and stress responses. The stress distributions and load bearing capacity of piles on Ryukyu Limestone Formation are analysed and their implications in foundation design are discussed.

Naohiko Tokashiki, Ömer Aydan, Takashi Ito, Yuji Shuri

Micromechanics of Pile Cyclic Response in Sand

A 3D discrete element model is used to investigate the axial cyclic response of a small-scale displacement piles installed in Fontainebleau sand. Calibration chamber experimental results from literature are used to validate the pile penetration phase of the DEM model which is then employed to simulate stress controlled vertical cyclic loading. The crushable DEM particle model is calibrated using high pressure element test data for the same sand. The model predicts the experimental stress measurements surrounding the jacked pile in both penetrating and unloaded conditions. The DEM model is used to assess micromechanical features hard to detect using experimental and continuum numerical methods. Grain crushing within the soil is observed to occur only below the cone during pile penetration. The analysis of particle stresses and force chains highlight how arching develops around the shaft. These arching effects create a sort of shield around the shaft causing the radial stresses to be lower. After pile installation is completed, a numerical parametric study of stress controlled cyclic axial loading of the pile is performed. The results show that depending on the magnitude of the cyclic load stable or metastable pile cyclic response is attained. The cyclic load amplitude also influences in different ways both stress and density profiles around the pile. These results may serve as a step forward to the understanding of installation effects on axial cyclic performance of jacked piles in sand.

Matteo Oryem Ciantia

Some Remarks on the Seismic Design of Multipropped Retaining Walls

The behavior under seismic condition of embedded retaining structures is quite complex. When the geometry (prop levels) prevents the formation of kinematic mechanisms and the structural elements do not achieve yield strength conditions, permanent displacements are expected to be relatively low and, therefore, seismic actions may cause significant increases of the forces acting on the structures: these forces are dependent on a number of factors such as the characteristics of the ground motion, the problem geometry, the mechanical behavior of the soil and the soil-structure relative stiffness. In the present study, the results of several dynamic numerical analyses of a multi-propped retaining wall in a dry coarse soil are presented and discussed. The results of the analyses indicate that large structural stresses (bending moments in walls and axial loads on props) develop as consequence of seismic actions. Post seismic stresses remain significantly large as compared to the static condition. The maximum ground acceleration in the free-field seems not to be an effective parameter in order to evaluate the seismic performance of this kind of retaining structures.

Fabio M. Soccodato, Giuseppe Tropeano, Alessandro Aru

Numerical Analysis of Mechanical Characteristics of Joint Structure of Steel Pipe Sheet Pile Foundation

The aim of this study is to clarify the mechanical behavior of the joint parts in a steel pipe sheet pile (SPSP) foundation under horizontal loading. The foundation structure of SPSPs is constructed by coupling the joints of each SPSP in the ground with the injection of mortar into the joints. For this purpose, the mechanical behavior of the SPSP foundation should be discussed with a clear understanding of the mechanical behavior of the SPSP joints. In the design criteria under lateral loading, however, only the vertical shearing of the joint parts is considered as critical. Accordingly, the precise understanding of the lateral loading capacity of the SPSP foundation was investigated in this study through model experiments and a reproduction analysis by the 3D finite element method. Simply stated, from the lateral loading tests on the SPSP models and their reproduction analysis by a 3D FEM, it was found that the lateral loading causes vertical shear displacements of the joints of the piles arranged in parallel to the loading direction and almost no displacements of the joints of the piles arranged perpendicularly to the loading direction.

Yusuke Miyazaki, Yasuo Sawamura, Shoma Kusaba, Makoto Kimura, Tomohiko Nishihara, Takashi Kosaka, Masahiro Hattori, Kazuhiko Maekawa

Numerical Analysis of Shallow Foundations Considering Hydraulic Hysteresis and Deformation Dependent Soil-Water Retention

Shallow foundations are one of the most common methods for transmitting loads of structures to the underlying ground. Design standards are often based on the bearing capacity of shallow foundations in saturated soils or dry soils. However, many shallow foundations are located within unsaturated soil above the groundwater table. Although experimental studies show that the bearing capacity is significantly increased by the presence of suction in unsaturated soils, the foundation settlement caused by infiltration, e.g., due to rainfall and pipe leaking, may develop further problems for structures, such as wall cracks, sticking windows and doors and the presence of water in basements. This kind of damage is happening more often now, with more extreme weather conditions as a result of climate change. A finite element model has been developed in this paper to analyse shallow foundation behaviour under infiltration conditions. An advanced unsaturated soil model has been implemented in the finite element code that considers the soil-water retention with hysteresis and deformation dependency. Numerical analysis results indicate that the foundation settlement is significantly influenced by the hydraulic history (seasonal changes with drying-wetting cycles), and hydraulic hysteresis should be included in the numerical analysis of the mechanical response of shallow foundations in unsaturated soils.

Yue Zhang, Annan Zhou, Majidreza Nazem, John Carter

Numerical Investigation on Seismic Performance of a Piled-Raft Foundation with Grid-Form DMWs

In this paper, the seismic performance of a piled raft foundation combined with grid-form deep mixing walls under a strong earthquake is investigated numerically. A 12-story building on the soft clay ground was modeled using a three-dimensional finite element soil–structure interaction model. The model was calibrated using the seismic observation records of a middle-scale earthquake at the building site in the previous study. The elasto–plastic model used for the stabilized soil has the tensile criteria and the shear criteria, and the model has an ability to evaluate the post-peak softening. The analysis result indicates that the induced stress reaches the tensile strength in some parts of the deep mixing walls. However, few parts of them lose large amount of tensile strength as a result of post-peak softening. And the grid-form deep mixing walls are found to keep their function of reducing the bending moment of the piles to an acceptable level.

Y. Shigeno, K. Yamashita, Junji Hamada

Numerical Investigation of Failure Mechanism During Pullout of Root Inspired Anchorages

By looking at nature, modern and sustainable engineering solutions can be developed. For instance, fibrous root systems, have inspired new prototypes of foundations, tiebacks or anchorages. A possible configuration of these innovative shapes is a central shaft branched out with multiple arms. Small-scale experiments have shown how root inspired anchorages can bring benefits in terms of pullout capacity and material efficiency (Mallett et al. 2018a, b). However, the failure mechanism of the pullout of these anchors, is not yet fully understood. This paper contributes to examining this issue by means of numerical simulations conducted via the Material Point Method (MPM). Different geometries have been investigated, such as a 3-branched, a 6-branched and a plate anchor system. Special attention is given to the volume of mobilized soil and the shape of the failure surface generated during the anchor pullout. The numerical results are compared with those of small-scale experimental tests presented in Mallett et al. (2018a, b, 2017).

Ilija Vego, Francesca Ceccato, Paolo Simonini, J. David Frost, Seth D. Mallett, Simonetta Cola

Modeling Seismic Wave Propagation and Interaction: Recent Advances and Future Challenges

Modeling seismic waves and vibrations propagating into geological structures has always been a challenge since large scale models as well as detailed basin geometry and soil layering are both needed. The optimal accuracy to model the propagation process depends on the frequency range but also on the excitation level.Various numerical methods have been significantly improved along the years to achieve accurate and cost-effective strategies: FDM, FEM, FVM, SEM, BEM, DGM. The first key issue deals with numerical dispersion (link between wavelength and propagation features). Numerical damping may also be a (controllable) issue.Another important question is related to spurious reflected waves at the model boundaries. To reduce such errors, absorbing boundary conditions or absorbing layer methods (PML, CALM, ALID) have gained interest in the recent years.To model seismic waves propagating from the fault to the structure, a coupling strategy (DRM, FEM/BEM, strong vs weak) may be optimized to accurately model the wave radiation at infinity or accommodate large velocity contrast (i.e. large mesh refinement discrepancies).Future research challenges are also discussed: physics based fault rupture, nonlinear soil/rock behavior and characterization, loading history, pore fluids, uncertainties vs spatial variability, interaction with various structures at different scales.

J. F. Semblat, S. Chaillat, L. Lenti, K. Meza-Fajardo, M. P. Santisi d’Avila

Application of a Physical-Mathematical Model of Leachate Ion Diffusion Through Compacted Soils from Diffusion Tests

Molecular diffusion can transport ions from the leachate through a compacted soil barrier in landfills since it depends only on the concentration gradient. This mechanism is described by equations that depend on the effective diffusion coefficient in soils for each chemical element. Laboratory tests are necessary to estimate this coefficient, by testing a compacted soil layer subject to a contaminating solute, which results in curves of the variation of the concentration over time and along the soil thickness. The purpose of the paper is to apply the semi-analytical method called Equivalent Contaminated Layer Solution (ECL) for determining the diffusion and sorption coefficients for specific contaminants. It was adjusted a computational model that allows the calibration and visualization of diffusive tests in time and space, with a three-dimensional surface. The methodology was carried out using the software Wolfram Mathematica. The experimental data used were taken from previous studies. It was modelled the diffusion of chloride, chrome, cadmium, nickel and copper. The results of the models were validated for a hypothetical compacted clayey liner. The method applied allowed us to analyse the ion migration in compacted clayey liners from solid waste landfills.

Camilla Turon Baran, André Luís Brasil Cavalcante

A Nonlocal Elasto-Plastic Model for Structured Soils at Large Strains for the Particle Finite Element Method

This work presents a robust and mesh-independent implementation of an elasto-plastic constitutive model at large strains, appropriate for structured soils, into a Particle Finite Element code specially developed for geotechnical simulations. The constitutive response of structured soils is characterized by softening and, thus, leading to strain localization. Strain localization poses two numerical challenges: mesh dependence of the solution and computability of the solution. The former is mitigated by employing a non-local integral type regularization whereas an Implicit-Explicit integration scheme is used to enhance the computability. The good performance of these techniques is highlighted in the simulation of the cone penetration test in undrained conditions.

Lluís Monforte, Matteo Oryem Ciantia, Josep Maria Carbonell, Marcos Arroyo, Antonio Gens

Analysis of Undrained Cavity Contraction from Unloading Incorporating Different Degrees of Intermediate Principal Stresses

Cavity contraction problems exist in many engineering practices, such as wellbore engineering, pile drilling, tunnel excavation, etc. The unified strength theory considering the influence of principal stress in different degrees was applied to the unloading problem of cavity excavation. With the unloading factor and contraction coefficient introduced, the normalized similarity solution of cavity unloading-contraction was derived under undrained conditions. Compared with the solution without considering the influence of the intermediate principal stress using Mohr-Coulomb criterion, the concrete effects of different degrees of intermediate principal stresses, cohesion and friction angle on the unloading-contraction relationship are given: the larger the intermediate principal stress influence parameter b, the smaller the cavity unloading-contraction effect, and its essence is that the increase of b introduction of b makes elastoplastic boundary moving towards the cavity wall, delays the appearance of the peripheral peak hoop stress, and helps to reduce the cavity wall plastic zone. Based on the dimensionless unloading contraction similarity solution of cavity, a more reasonable quantitative prediction of the radius variation of cavity at a specified unloading degree can be performed for undrained soil.

You-Bao Wang, Cheng Zhao, Chunfeng Zhao, Yue Wu, Xin Gong

A Numerical-Analytical Method for Dynamic Analysis of Piles in Non-homogeneous Transversely Isotropic Media

This paper presents a novel numerical-analytical method for dynamics of piles embedded in non-homogeneous transversely isotropic soils. In the method proposed, the piles are modelled using beam-column elements, while a new type of elements called radiation discs are defined at the nodal points of the elements to simulate the wave propagation through the non-homogeneous soil medium. By using radiation discs, the discretisation is only required along the length of piles, while discretisation of surrounding medium, top free surface boundary, and cross sections of piles are avoided. Numerical results are presented and the effect of soil non-homogeneity on lateral compliances of piles and pile groups is particularly emphasised.

B. Shahbodagh, H. Moghaddasi, N. Khalili

DEM Modelling of Ice Filled Rock Joints

The research we present in this paper is part of a wider project about the modelling of climate change effects on the degradation of permafrost, with particular attention for the stability of rock masses. The presence of ice and/or mixtures of ice and granular materials in rock joints has a big impact on the shear resistance of joints and on the evolution of joint persistence. In previous research we modelled the mechanical behavior of ice and frozen soils with a Distinct Element model and compared the evolution of the resistance with ice content with experimental data available in the literature. In this paper, we are focusing on rock joints and we are modelling both fill material (ice and frozen soil mixtures) and rock as collections of Distinct Elements, taking advantage of the previous experience in terms of calibration of the parameters. In particular, in this preliminary study, we will focus on the shear resistance of joints as a function of the composition of the fill material. The purpose of this research is to study the mechanical behavior of joints and derive the corresponding force-displacement relationship to be assigned to the interfaces between blocks in a full scale model of rock masses.

Guodong Wang, Francesco Calvetti

Numerical Simulation of Progressive Slope Failure Using the Smoothed Particle Finite Element Method

In this paper a novel node-based explicit smoothed particle finite element method (SPFEM), is utilized to evaluate the progressive slope failure mechanisms. In the SPFEM approach, a node integration method (strain smoothing technique) is introduced into the framework of the particle finite element method (PFEM). The main advantage of SPFEM in slope stability analysis lies in its capabilities to consider the whole dynamic failure process of slope and to simulate large deformation and post-failure of soils. The progressive failure behaviour of a long clayey slope is modelled using SPFEM in conjunction with a strain-softening Tresca constitutive model. The retrogressive failure behaviour of a long clayey slope is analyzed.

Wei-Hai Yuan, Hao-Cheng Wang, Wei Zhang, Bei-Bing Dai

Granular Mechanics of the Active Lateral Pressure on Retaining Walls Rotating About the Top

In granular soils, stresses are transmitted by chains of contact forces from grain to grain. In this work, the average stresses are obtained based on two simplifying hypotheses: the linearization of the chains, and their association with bands of soil. In this way, the intersection of two conjugate bands gives rise to the definition of the basic element of the granular soil: the rhomboid, whose weight is resolved into two unitary forces of contact, which are added along an associated band to achieve the resultant force acting on the back face of a rigid retaining wall. As the kinematics of a wall rotating about its top requires that the lower grains rotate with respect to the upper grains of the backfill, the contact force against the wall follows a passive direction, whereas the conjugate force remains at the original direction, given by the at rest stress state. Because of the angle of the passive chain is greater than the failure angle, the lateral pressure becomes bilinear, with the maximum value near the top, in agreement with the experimental results of several authors. Hence, the lateral force is similar to that of Coulomb, but the point of application is higher.

Calixtro Yanqui

Tunnelling-Induced Displacements and Damage on Framed Structures: Comparison Between Numerical Models

The paper focuses on the response of framed structures to tunnel excavation in sand. Standard 3D Finite Element analyses, in which the structural elements are explicitly detailed, as well as simplified equivalent beam models were adopted to simulate the influence of the frame and that of the masonry infills. Both approaches well captured the main soil-structure interaction mechanisms. The presence of stiff masonry infills was found to reduce the angular distortions of the frame bays and, as such, to reduce the tunnelling induced damage. For the first time, insights into the efficiency of two-stage models implementing equivalent Timoshenko beams for framed buildings are given.

Daniela Boldini, Nunzio Losacco, Andrea Franza, Seyedmohsen Miraei

Numerical Modeling of 3D Site-City Effects Including Partially Embedded Buildings Using Spectral Element Methods in Medium Stiffness Soils

In recent years, seismic wave propagation analyses have become a powerful tool to evaluate the site effects in a given region. Among several approaches, the Spectral Element Method (SEM) has been widely used with that purpose because of its flexibility and computational efficiency. The multiple interactions between the soil and structures, denominated site-city effects (SCI), can play a crucial role in densely populated areas. There are many options to model this kind of interaction, especially if the buildings are partially embedded on the soil. This paper evaluates the importance of the proper SCI modeling against more standard uncoupled approaches, focusing on the local interaction between the soil and a group of buildings including inelastic soil behavior. We focus our work on the case of downtown Viña del Mar, a touristic coastal city of central Chile, where the observation of a reiterated distribution of damage in reinforced concrete buildings during two major earthquakes has motivated numerous studies. For that purpose, a realistic 3D numerical model of the area is created, considering the existing buildings. In general, the results indicate that the inclusion of the SCI reduces the maximum interstory drift in most cases, and that the SCI modeling needs to considerate the level of embedment to obtain more precise results.

Valeria Soto, Esteban Sáez

Discrete Element Modeling of Compound Rockfall Fence Nets

Compound mesh panels are structures in which two different nets geometries are employed: a main mesh that provides the bearing capacity and a weaker mesh with a thin sieve size to catch smaller blocks that can pass through otherwise. Typically, only the effect of the main mesh is investigated, and the weaker mesh is considered to provide negligible structural resistance. In this paper, after a calibration procedure, numerical simulations of quasi-static punch tests and a dynamic block impact on a composite double-twist and strand rope mesh are performed. The results show that, under dynamic conditions, the presence of the finer mesh lowers the peak force acting on the main mesh. This effect is not found under quasi-static conditions and has important repercussions on the overall structural resistance as the energy dissipation mechanism reduces the stress on the mesh fence posts.

Marco Previtali, Matteo Oryem Ciantia, Saverio Spadea, Riccardo Castellanza, Giovanni Crosta

Large Deformation Finite Element Analysis of CPT in Calcareous Sands

The tip resistance measured within the cone penetration test (CPT) can be used to predict the pile tip resistance under axial loading, due to the geometric similarity. Most of the existing correlations were established in terms of siliceous sands, while the data for calcareous sands are limited. Calcareous sands in situ are featured with higher peak internal friction angle, but the strength reduction may be significant due to particle breakage. In this paper, a large deformation finite element approach, the Abaqus finite element package utilizing the Arbitrary Lagrangian Eulerian method (ALE) is used to study cone penetration in calcareous sands. A constitutive model proposed by Yin et al. (2016) and Wu et al. (2017) is incorporated into ALE to describe calcareous sands. The CPT in silicon sands is replicated by a modified Mohr-Coulomb model as well for comparison purpose. Frequent mesh generations are conducted in ALE, to avoid distortion of soil elements around the cone tip.The numerical results of cone tip resistance agree reasonably well with the existing data from centrifuge tests. It demonstrates that the modified Mohr-Coulomb and SIMSAND-Br models have potential to capture the behaviors of silica and calcareous sands. The cone resistance in calcareous sands is found to be affected remarkably by particle breakage around the cone.

Huimin Pei, Dong Wang, Zhenyu Yin, Qingbing Liu, Jingbin Zheng

Soil-Building Interaction and Risk Assessment of Existing Structures During Mechanized Tunneling

During the planning phase of tunneling projects, in particular in urban areas, it is crucial to assess the likely extent of structural damage caused by the tunnel construction in close vicinity to existing surface structures. Tunneling inevitably causes ground movements which in turn may have an impact on deformations and stresses of the above-ground structures. For this reason, a reliable estimate of the soil-structure interactions due to tunnelling-induced settlements is essential. In this contribution, various approaches that differ in precision and complexity are employed to predict the magnitude of expected settlements and the vulnerability of structures with regard to tunneling induced damage. In addition, a three-step damage assessment concept adjustable to the necessary level of detail is suggested. Firstly, ground movements are predicted using analytical or numerical approaches. Secondly, the above-ground structures are idealized by means of surrogate beam-, slab- or 3D-models. Finally, structural damage is assessed according to the computed strain pattern or the tilt of the building. This method enables the evaluation of the potential damage to above ground structures associated with planned tunnel alignment. When developing 3D numerical models, the main focus will be to ensure that the building and the soil-structure interactions are represented with an appropriate level of detail. To this end, this paper aims to provide recommendations for a sufficient level of detail (LOD) of surface structures for the assessment of tunneling induced damage in computational simulations in mechanized tunneling.

Abdullah Alsahly, Ahmed Marwan, Markus Obel, Peter Mark, Günther Meschke

Effect of Ground Parameters on Housing Settlement Prediction by Simplified Liquefaction Analysis

Severe damages such as large settlement and tilting of detached houses have been often observed due to ground liquefaction in the Great East Japan Earthquake. Liquefaction countermeasures were not adopted for the detached houses since the house owner couldn’t understand the potential of the liquefaction damage. In order to adopt countermeasures for detached houses, the appropriate prediction of the damage is necessary. In this study, SPH simulations with different material parameters such as FL and Fc were carried out targeted for 1-g shaking table tests to understand the effect of ground parameters on housing settlement prediction.

Hiroshi Yokawa, Hideto Nonoyama, Atsushi Yashima, Shotaro Higuchi, Toshio Sugii

A New Sand Constitutive Model for Pre- and Post-liquefaction Stages

A new model, named SANISAND-MSf, is presented that is an extension of the two-surface constitutive model within the framework of bounding surface plasticity. It addresses the modeling of sand behavior under undrained cyclic loading by successful simulation of stress-strain curves, undrained stress paths and strength curves, for various cyclic stress ratios and loading conditions, at both pre- and post-liquefaction stages separately, as opposed to overall simulations of past efforts. The model incorporates a new form of a memory surface for the pre-liquefaction stage and the concept of semifluidized state for the post-liquefaction stage; both address the proper modification of stiffness and dilatancy. The formulation avoids common shortcomings of previous models related to stiffness degradation and singular analytical eventualities. The SANISAND-MSf maintains the well-known ability of the two-surface bounding surface model to simulate successfully monotonic loading at various pressures and densities with one set of model constants and be critical state compatible. This paper addresses the novel capabilities of the proposed model in capturing the challenging aspects of modeling seismic site response analysis of a soil deposit in both pre- and post-liquefaction state of response. The developed modeling framework will contribute to future applications in a realistic and thorough seismic site response analysis.

M. Yang, M. Taiebat, Y. F. Dafalias

The Simulation of Loading and Excavations as Dynamic Problem and Their Comparison with Static Solutions

Loading and excavation are fundamentally dynamic processes. However, the dynamic effects are often neglected if the overall system is stable following the transient stage. However, there are some cases such that the dynamic processes may result in some damaging effects, which may not be expected from static solutions. In this study, the author consider some typical loading and excavation situations as dynamic problem and evaluate the dynamic variations of strain and stress and compare the results with static solutions. The computed results clearly show that strain and stress states may be much higher than those from static solutions and they may have important implications in practice.

Ömer Aydan

Influence of Masonry Building Characteristics on Tunnel-Induced Building Damage

Deformations and damage induced in masonry buildings due to nearby tunnel construction activities are influenced by various factors relating to the ground conditions and the structural characteristics of the building and its foundations. The current paper draws on recently completed work at Oxford University, UK on three-dimensional (3D) finite element studies on the influence of the foundation and building characteristics on computed tunnel-induced tensile strains in a masonry building, for an idealised form of the problem. Results are presented on the influence of choices on the constitutive model employed for the masonry and the incorporation of openings (for windows and doors) in the building façade; computed damage metrics are shown to be strongly influenced by these two aspects of the model. It is shown that some of the features of these 3D finite element models can be approximately represented by a simplified model employing an elastic building and a nonlinear Winkler soil-foundation interaction model.

Harvey Burd, Wing Nam Yiu, Christopher M. Martin

Seismic Response Analysis of Liquefiable Sandy Ground Considering Inherent Anisotropy’s Influence

Consideration of inherent anisotropy is crucial to gaining an improved understanding of the behavior of granular materials. One of the authors examined inherent anisotropy’s effect on the seismic behavior of ground through dynamic centrifuge model tests and revealed that a sandy level ground deposited at a higher angle is more susceptible to liquefaction. In the present paper, seismic response analyses are performed on the liquefiable sandy ground considering inherent anisotropy and their results are compared with the experiment. For modeling the sandy ground, a strain space multiple mechanism model is used; the model has been expanded for describing sand behavior associated with inherent anisotropy, by introducing three anisotropic parameters (a1, a2, and θo). The seismic response analyses with no consideration for permeability anisotropy show that it is difficult to accurately simulate the deposition angle dependency in the experiment, even though the additional anisotropic parameters are employed. This study demonstrates that considering anisotropic permeability, which may depend on the deposition angle, is required as well as the additional three parameters for properly capturing the liquefaction behavior of sandy ground associated with inherent anisotropy.

Kyohei Ueda, Junichi Hyodo, Kyohei Sato, Yoko Sugiura

Dynamic Numerical Analysis of the Mazar Concrete Faced Rockfill Dam in Ecuador – South America

The catastrophic effects of earthquakes that frequently hit the West coast of South America has motivated this research. The country of Ecuador, situated on the subduction border of the South American and Nazca tectonic plates, has a high seismic exposure. Since the Mw = 7.8 earthquake that occurred on April 16th, 2016, the assessment of stability conditions of dams has become a high priority for the Ecuadorian government. The concrete faced rockfill dam (CFRD) of Mazar, an essential structure for the country, is classified as a large dam by the International Commission on Large Dams (ICOLD). In this research, the numerical seismic analysis of Mazar dam was carried out, including the generation of artificial earthquakes based on acceleration spectra established by Ecuadorian standards. Other aspects related to the dam behavior were also investigated, such as the static and pseudo static stability conditions and the maximum permanent displacements determined by simplified methods. An important conclusion from the 2D numerical analysis is the influence of topographic amplification, which is not taken into account when simplified methods based on 1D wave propagation are used.

D. Velez, C. Romanel

Geomechanical Evaluation of CO2 Storage in a Coal Seam with a Secondary Barrier

Geomechanical evaluation of CO2 underground disposal is complex and can be even more challenging in coal reservoirs due to natural fractures and combined effects of multi-component transport. The objective of the research work presented in this paper is to investigate the geomechanical response of the geologic system due to large-scale CO2 injection in a targeted coal reservoir. Field-scale geomechanical models were constructed to capture overall geologic response at an active site due to injection, and the results were compared with long-term field monitoring work. Coupled multiphase fluid flow and geomechanical models developed for the project site are capable to understand the CO2 transport behavior within the targeted reservoir and geologic layers above the targeted reservoir. Additionally, modeling efforts were carried out to investigate CO2 transport behavior and geomechanical response, if CO2 were to break through the seal layer into overburden formations. The combined results of geomechanical modeling and tiltmeter monitoring provide useful information on the migration of CO2. Modeling results show that a secondary coal seam above the targeted coal reservoir could potentially acts as a barrier in the presence of a CO2 leakage.

Hema Siriwardane, Raj Gondle, Zainab Jawad

Study of the Earth Pressure of the Finite Soil Layer

A planar sliding landslide with a finite soil layer is located in Anhui province. Soon after the retaining wall was built, cracks appeared in the wall. It is necessary to obtain the value and distribution of the earth pressure behind the wall. The distribution law of earth pressure behind the wall cannot be obtained by using classical Rankine and Coulomb earth pressure theories directly. Therefore, in this work, three methods were adopted to study the earth pressure of the finite soil layer on the retaining wall. 1. Graphic method. Based on the Coulomb theory of earth pressure, the vertical upward cohesion Ca is added and the earth pressure is obtained according to the force vector polygon. 2. Conversion overloading method. The soil beyond the top of the wall is converted into the overload effect on the soil, and then Rankine theory is used to calculate the earth pressure. 3. Numerical analysis method. Finite element software was used to simulate the slope under natural conditions. Based on this study, it was concluded that the value of the earth pressure calculated by the graphic method is the minimum, whereas that obtained by the overload calculation is the maximum. The distribution of earth pressure obtained by numerical simulation of the limited soil mass first increases, then decreases and then once again increases from the top to the bottom of the retaining wall.

Du Yi-han, Liu Xuan-yu, Jiang Min

Is It Possible to Build a Rock Cavern for Compressed Air Energy Storage at a Shallow Depth?

Compressed air energy storage (CAES) is considered as a promising energy storage solution to balance the energy load leveling. The previous engineering practice usually locates the air storage caverns at deep locations from the surface of the earth. This study conducts a numerical analysis to evaluate the possibility of building a rock cavern for compressed air energy storage at a shallow depth. The results show the sealing layer could stop the compressed air from leaking out and contain the heat energy in the storage cavern due to its excellent adiabatic performance. The heat transfer in the structures of the cavern had a hysteresis effect which should not be neglected in the further study. The stress and strain in the surrounding rock were both within the capabilities of the materials. The results confirmed the feasibility of CAES in the lined rock caverns at shallow depth from the aspect of the numerical simulation. It provides a theoretical basis for the following pilot cavern.

Dong Tang, Xinmin Zhang, Zhongming Jiang

Prediction of Slope Failure in Cold Regions Induced by a Rainfall During Snowmelt Period

In cold regions, soil slope failures frequently occur due to an increase in the degree of saturation of soil by snowmelt and rainfall infiltration. However, studies related to the coupled effects of snowmelt and rainfall infiltration in cold region are very limited. This paper studies a soil slope failure occured on snowmelt period at a natural cut slope of the expressway in Hokkaido, Japan. According to the disaster investigation report, the slope failure was occured by inflitration of snowmelt, rainfall and overflow water from the drainage ditch. To investigate the cause of the slope failure, reproduction analysis which includes the three-dimensional unsaturated/saturated seepage analysis and slope stability analysis was performed. The numerical simulation considers the effects of snowmelt, rainfall, overflow from drainage ditch and surface grass. It is concluded that the overflow from the drainage ditch had serious effects on this slope failure. Moreover, the numerical simulation approach can reproduce the slope failure caused by infiltration of snowmelt, rainfall and overflow from drainage ditch.

Takumi Murakami, Tatsuya Ishikawa, Nguyen Thanh Binh, Akira Mori, Seiya Yokota

The Role of Internal Characteristic Length in Slope Stability Analysis with Strain Localization

Nowadays, most slope stability analyses have been performed without considering the effects of shear band width. To improve the estimations, the shear band width was adequately modeled by introducing an internal characteristic length (lc) within the Cosserat continuum framework, and hence the recently developed second-order cone programming optimized Cosserat continuum finite element method (named CosFEM-SOCP) is employed to investigate the effects of shear band width on slope stability. Based on a homogeneous slope example, it can be recognized that neglecting the shear band width for a slope may lead to overly conservative estimations on the FOS of the slope.

Xi Chen, Dongyong Wang, Jianbin Tang, Yuzhen Yu, Yong Liu

Testing of a Novel Energy Wall System in Torino

The need of renewable energy sources is increasingly pushing the design of new and renovated buildings as a result of compelling regulation in the construction sector. On the one hand shallow geothermal energy is suitable as a sustainable and distributed energy source. On the other hand, significant installation cost related to drilling of traditional installations represent a hampering factor. Energy geostructures as piles, diaphragm wall, tunnels and anchors include these costs in the construction of primary or secondary structural elements. Major part of building heritage in urban areas present underground levels that can be equipped with heat exchangers.This paper introduces the concept of a modular very shallow geothermal exchanger as part of a Heating, Ventilation and Air Conditioning (HVAC) system. The system is conceived to externally equip with heat exchangers the earth-contact area of underground walls that are generally widely available in residential and commercial buildings. An experimental site consisting of three modules of the above mentioned technology was designed by the authors and installed in an office building in Torino (Italy). Pipes were placed externally to the basement wall in two different arrangements. A large number of sensors were placed to monitor the additional stresses and strains on the wall and the thermal regime of the partly saturated ground volume involved in heat exchange. A comprehensive view of the main components of the prototype and the related monitoring system are given together with preliminary thermal performance results.

Matteo Baralis, Marco Barla

Laboratory Tests of Fully Grouted Bolts with a Pumpable Thixotropic Resin

Rock bolting is a ground reinforcement technique broadly used not only in mining but also in civil engineering applications. A rock bolt consists of a bar inserted in a borehole that is drilled into the surrounding soil or rock mass and secured to it generally with a binder, which can be cementitious or resin based. Cementitious grouts require several hours to harden and resin cartridges might lead to shortcoming such as poor mixing, collapsed boreholes prior to insertion, and insufficient resin volume for full encapsulation due to enlarged boreholes. A novel pumpable thixotropic resin based on polyurea silicate has been developed in order to overcome the issues of conventional resin cartridges, to ensure a quick curing time within seconds and to be able to install bolts on the roof. Several mechanical pull-out tests on hollow and solid rock bolts according to DIN 21521 have been performed in order to assess the ultimate failure for the novel pumpable thixotropic resin. Results are very useful to contractors and designers to understand the mechanical response of a novel thixotropic resin.

Giovanni Spagnoli, Davide Carnelli, Uwe Wyink, Christoph Herrmann

Discontinuum Mechanics of the One-Dimensional Consolidation of Soils

This paper deals with the one-dimensional primary consolidation of saturated fine-grained soils, described as a discontinuum process. The theory is based on two foundations: the ideal discrete space-time structure of matter, and the principle of the mean value. Discontinuous matter is described by the influence domain of a point or node. Since this domain is a statistical sample of the whole discontinuous body, any associated quantity may be described properly as a point estimator, which is determined by averaging the neighboring values within the influence domain. As a consequence, a parabolic differential equation is attained. When this estimator is linear and logarithmically related to the excess porewater pressure, the settlement, or the vertical strain of a fine-grained soil subjected to the consolidometer test, the theories proposed by Terzaghi, Davis and Raymond, and Mikasa can be weighed, and the abundant reported experimental data may be used to develop deductive relationships between the consolidation parameters.

Calixtro Yanqui