Proceedings of GeoMandu 2024 Volume 3

Table of Contents

1. Frontmatter

2. Benefits of Including CPTu in Geotechnical Investigation Program—A Case Study

   Sorabh Gupta, Ravi Sundaram, Sanjay Gupta

   Abstract

   Modern testing technologies such as electric cone penetration test with pore water pressure measurement and SPT energy transfer measurements can generate reliable geotechnical parameters for foundation design that is usually somewhat higher than that justified from conventional borehole data only. A case study of an industrial grain silo project is presented here that illustrates the savings that can be achieved by including electric cone penetration test with pore pressure measurement (CPTu) and SPT energy transfer measurement in the scope. Various engineering parameters, such as undrained shear strength of cohesive soils, angle of internal friction of granular soils, bulk density, over-consolidation ratio, modulus of elasticity, constrained modulus, etc., have been computed from the cone tip resistance values using published correlations developed by Robertson which are proven and used worldwide. Detailed foundation analysis was performed to determine the safe bearing capacity and settlement of foundations by conventional analysis using borehole data and compared with the safe bearing pressures that can be justified by use of CPTu results. The significantly higher safe bearing pressures justified resulted in considerable economy in foundation cost. The need for ground improvement by stone columns for the silo raft could be eliminated resulting in substantial savings in the foundation cost.

3. GPR Mobile Mapping System 3D (GMS3)—A Unified Surface and Subsurface Spatial Information System

   Jun Shinohara, José Maria dos Santos Rodrigues Neto

   Abstract

   GPR mobile mapping system 3D (GMS3) is a system that combines three-dimensional ground-penetrating radar (GPR) subsurface data synchronized with 360° camera surface mobile mapping system (MMS) imagery to provide an integrated surface–subsurface spatial information database where subsurface features are easily localizable from surface imagery. The MMS system also provides correction of raw Global Navigation Satellite System (GNSS) data through camera vector (CV) processing of surface imagery, allowing for high-precision localization of the database. The system’s main applications are road subsurface cavity detection and mapping for prevention of sinkholes and mapping of buried pipes and other underground infrastructure. Both applications are in high demand in Japan, in part due to the country’s high susceptibility to earthquakes, as well as its delay in undergrounding of overhead cables. It is expected that GMS3 can be a valuable spatial information system in subsurface and surface mapping.

4. Strength and Durability Characteristics of Reclaimed Pavement Material Using Full Depth Reclamation (FDR) Technique

   Shilpa Mary Sam, P. Seethalakshmi, Prateek Negi

   Abstract

   The flexible pavements in the lateritic terrain of Kerala, India, are often affected by the heavy monsoon rains, leading to the deterioration of roads. For such vulnerable low-volume roads, the application of the full depth reclamation (FDR) technique was noticed to be a cost-effective and environment-friendly technique that can improve the bearing capacity and reduce cracking in pavements. This technique stabilizes the deteriorated pavement with cement and chemical admixtures by reusing the existing pavement section material. In the current experimental study, an attempt was made to adopt FDR utilizing the Lateritic Reclaimed Pavement Material (RPM) collected from rural roads in Kerala to create a cement-treated base layer along with suitable accelerating admixture to acquire the target strength parameters and durability properties of the flexible pavement. The percentage of the admixture was fixed at 4% of cement, and the cement percentage was varied from 4 to 5% by weight of the RPM. The gradation, Atterberg limits, maximum dry density, and optimal moisture content of RPM were determined as per IS Codal provisions. Further, the RPM was mixed with varying cement percentages and admixtures to understand the improvement in strength and durability characteristics. The stabilized RPM was subjected to unconfined compressive strength, flexural strength, and durability test procedures under 7- and 28-day curing times. The results showed an improvement in compressive and flexural strength with curing time and were found to be highly durable with merely ~ 5% material loss at the end of the test.

5. Design of Tunnel Support System, Shotcrete Versus Rock Bolts in Middle Modi Hydroelectric Project (MMoHP)

   Milan Paudel, Akal Bahadur Singh, Mohan Raj Panta

   Abstract

   Middle Modi Hydropower Project (MMoHP) is located in Himalayan geology with tectonically youngest geological formations in Nepal and seems challenging for the construction of underground structure like tunnels. Although tunnel support system designs are explained in literature and previous studies, the limitations are mostly attributable to the specific geological conditions and conventional methods of shotcrete and rock bolts, which created the necessity of this research. This research aimed to assess the benefits of the shotcrete tunnel lining method over the other conventional methods in terms of time and economy by conducting the empirical, numerical modeling method. The parameters from rock support system using rock tunneling quality index (Q-value) were used in numerical analysis for conventional rock bolts and shotcrete versus steel fiber reinforced shotcrete (SFRS) support system which was performed by Phase² Software in two chainages 1 + 000 m and 2 + 400 m. The maximum displacement around tunnel contour was found less than 3 mm in first section and 50 mm in second section. Furthermore, the change in thickness of the shotcrete in case of shotcrete and rock bolts and in case of shotcrete only was found 150 mm and 200 mm for first and second sections, respectively. After economic analysis, this study concludes that steel fiber reinforced shotcrete (SFRS) will be more cost- and time-effective than conventional wire mesh shotcrete and rock bolts.

6. Understanding the Effect of Soil Types in Bearing Capacity for Shallow Square Footings

   Ujjwal Niraula, Shreya Shrestha, Upendra Shrestha, Meera Neupane, Suresh Raj Joshi

   Abstract

   The common issue in foundation design is how the bearing capacity of a soil varies with variation in soil types and how the presumptive estimation of bearing capacity of soil may lead to unsafe designs. The factors that most significantly influence the bearing capacity of soil are friction angle, cohesion, unit weight, and depth and width of foundation. This study explores the soil behavior in shallow foundation, through an analysis of 40 distinct soil types and variations of all these parameters, which are derived from literature surveys. The goal of the study is to clarify how several soil characteristics interact with bearing capacity. However, presuming the bearing capacity of soil without analyzing the soil is a common practice among foundation designers in most of the cases. The results of this study, however, suggest that clay and high plastic silt soils commonly have reduced bearing capabilities and fall below the presumptive barrier. These findings cast doubt on the widely held design presumptions and highlight how crucial it is for engineers and designers to make well-informed decisions. Additionally, this investigation identifies the soil with the lowest bearing capacity and examines the impact of shallow footing depth (from 4 to 7 feet) and breadth (from 4 to 7 feet) changes in these soil types. For instance, in such soil, modest increase in the footing depth feet resulted in better increment in bearing capacity. In regions with poor soil profiles, practitioners can improve the safety and dependability of structure designs by emphasizing these linkages. This study explores on various ways by which soil properties impact the soil bearing capacity in shallow foundations, and it aims to provide information which may be used to make better judgements especially in regions with lower soil properties.

7. Stress and Deformation in Twin Tunnel and Support Design Optimization at Sanga Pass—Nepal Using Numerical Modeling

   Susmita Aryal, Satyam Yadav, Swostika Dhakal, Tanuj Bhatt, Sudarshan Gautam

   Abstract

   Stress and deformation behavior are essential for ensuring structural stability and safety of tunneling projects. Numerical modeling has emerged as the most reliable approach for precisely evaluating stress and deformation, enabling more informed decision-making in tunnel design and support systems. This study proposes a tunnel alignment in the Lesser Himalayan Region of Nepal at Sanga Pass based on field-acquired rock joint data. It utilizes RMR and Q values from line geological mapping to characterize the rock mass. The support is then designed for horseshoe-shaped twin tunnels using an empirical approach, and a detailed 2D finite element continuum model is employed to predict stresses and deformation using Phase2 software. The results from this numerical simulation provide valuable insights for designing and optimizing appropriate tunnel support systems.

8. Finite Element Analysis of Piled Raft Foundation System

   Kamalika Das, Akhileshwar Kumar Singh, Yadavendra Pratap

   Abstract

   The piled raft foundation system, which combines raft and pile foundations, addresses potential excessive settlement despite sufficient bearing capacity by having piles control settlement. In contrast, the raft bears the superstructure's load. Settlement behaviors of these foundations were analyzed using a 15-noded plane strain model in PLAXIS 3D. Factors such as raft thickness, length of pile, spacing between piles, and number of piles were studied to determine optimal design parameters, including the best pile location. The soil and piles were modeled with solid finite elements, and the raft was represented using first-order shell components. Nonlinear soil behavior was modeled using a cap model with three yield surface segments. Contact zones between soil and raft, and soil and high-diameter drilled piles, were represented using thin solid continuum elements. The raft and piles have been assumed to act linearly and elastically. In-situ subsoil conditions comprised Frankfurt clay overlain by Frankfurt limestone, simulated using an elastoplastic cap model. Young's modulus distribution of Frankfurt clay with depth has been considered nonlinear in PLAXIS modeling, with parameters chosen from stacked raft system elements. It has been observed that increasing the concentration of piles around the center of a uniformly loaded piled raft foundation of a rectangular plan reduced differential settlement. While adding piles reduced settlement, increasing their number beyond a certain threshold had no effect in further settlement reduction. Stiffnesses of both raft and pile group elements significantly influenced total and differential settlement in piled raft systems. Additionally, increasing the raft thickness up to 2 m substantially reduced settlement compared to shallow raft foundations.

9. Impact of Multilayered Fibre Reinforced Shotcrete on Structural Integrity: A Study in Underground Mining

   Greg You, Thomas Hocking

   Abstract

   Fibre reinforced shotcrete (FRS) is commonly used in underground mining, tunnelling, and many other applications to support the stability of the substrate structure. Thick shotcrete must be sprayed in multiple layers due to either the constructional need of the composite structure or operational need of preventing shotcrete fall or wet decohesion. The purpose of this study is twofold. The first one is to conduct a systematic review of shotcrete, fibre reinforced shotcrete, typical tests and strength values, and failure modes of shotcrete. The second one aims to investigate the effect of multilayered FRS on the uniaxial compressive strength and flexural toughness. The study was conducted in an underground mine in Australia and the test results were compared with the data of quality control and quality assurance (QCQA) in the mine. Rectangular and round panels were sprayed with a pause of 12 h between layers. The rectangular panel was used to core samples for compressive tests and round panels were for flexural toughness tests at 28 days age. It is found that it is impossible to distinguish the layer boundaries on the crosscut of the rectangular panel, or no cold joint on the interface of multilayered fibre reinforced shotcrete. Furthermore, both the compressive strength and flexural toughness meet the QCQA criteria applied in the underground mine, and there is no reduction in the compressive strength of multilayered fibre reinforced shotcrete and an insignificant difference in the flexural toughness.

10. A Case Study on Stability and Economic Analysis of Earthen Dam

    Milan Paudel, Bikash Devkota

    Abstract

    The selection of dam types and their stability is influenced by various factors such as material availability, financial resources, environmental and geographical constraints, and societal concerns. Nepal has a great variation in geological formation ranging from plain areas in the southern part to high hills/mountains in the northern part. Embankment and earth-fill dams can represent predominant choices in contemporary development projects in the southern region of Nepal. This study focuses on the design and stability assessment of an earth-fill dam using GeoStudio software to retain a required height of water. Numerical simulations were performed for optimizing dam’s cross-section. Besides, the cost of the earth-fill dam was compared to the rock-filled dam so that the scarcity of rock/stones in the low land area could be evaluated. The findings of this research can be useful for policymakers, local governmental bodies, and implementing agencies for the cost optimization of dam construction considering the local resources.

11. Assessment of Underground Powerhouse for Seti Nadi-3 Hydroelectric Project

    Darshan Babu Adhikari, Mohan Prasad Acharya, Gyanendra Lal Shrestha

    Abstract

    Selection of underground powerhouse location is crucial for the success of hydroelectric projects. This study presents the assessment of underground powerhouse for the Seti Nadi-3 Hydroelectric Project-87 MW in western Nepal. Geological assessments identified the dolomite rock band as favorable, leading to detailed investigations involving short drill holes to gather rock samples for laboratory testing. Numerical modeling was employed to evaluate location based on in situ stress conditions, validate rock support adequacy provided by Q-system, and ascertain sufficient vertical and lateral rock cover. The study also involved optimizing cavern orientation through rock mass joint analysis, assessing potential wedge block movements, and cross-referencing data from the World Stress Map. These analyses led to the finalization of the underground powerhouse location and confirmed that the proposed rock support system is sufficient to ensure cavern stability, with adequate vertical and lateral coverage. The findings of this study provided valuable insights into the assessment process for underground powerhouse in challenging geological environments. The results obtained were useful for optimizing the design and construction phases of the Seti Nadi-3 Hydroelectric Project, ensuring its long-term reliability and effectiveness in harnessing hydropower resources. The methodology used may provide guidance to other similar projects.

12. Behavior of Axially and Laterally Loaded Pile in Layered Soil

    Sushil Acharya, N. P. Kaushik, Bhashkar Pathak

    Abstract

    Pile foundations are crucial for structures such as bridges, high-rise buildings, and wharves in weak soil, where fine-grained soils exhibit high shaft friction and low-end-bearing resistance, while coarse soils exhibit the opposite characteristics. Determining both lateral and axial capacities is vital due to various sources of lateral loads alongside axial loads. This paper investigates the behavior of vertical single pile subjected to both axial and lateral loads in layered soil conditions, utilizing GEO5 software alongside field data. It aims to correlate the lateral and axial load capacities of vertical piles according to IS code IS2911 Part 1 (Sec 2), comparing the results with software analyses. The study considers various length-to-diameter ratios (L/D) and fixed-head pile conditions, examining both cohesive and cohesionless soil scenarios. Increasing pile diameter with constant length enhances load capacities and lateral deflection, highlighting differences between IS 2911 Part 1 (Sec 2) and Geo5 software, while altering pile length with constant diameter affects axial load capacity and maintains consistent lateral load capacity on sand and clay.

13. Analysis of Roadside Landslides in Nepal: A Case Study of the Inarpani Landslide on the Midhill Highway

    Kalpana Adhikari, Kiran Kumar Maharjan, K. C. Rajan, Susmita Timalsina, Biraj Ojha

    Abstract

    The introduction of roads in mountainous regions often induces instability, demanding site-specific knowledge for effective mitigation. This study examines a case of slope failure at Inarpani in Baglung along the Midhill Highway, revealing critical instability issues. Three Electrical Resistivity Tomography (ERT) profile surveys were conducted to uncover the lithology of the landslide area, followed by drilling of two boreholes for subsurface inspections and sample extraction for laboratory tests. Using the collected data, a GEOSTUDIO model was prepared for the critical section, with SEEP/W and SLOPE/W employed for slope analysis. The SLOPE/W analysis resulted in a very low factor of safety, on both the hillside (0.791) and valley side (0.799) of the road. The investigations and SEEP/W analysis identified the high groundwater table on the sand-dominant slope as the primary cause of failure. These findings highlight the need for effective water management to improve stability. Proper investigations and resolution of critical concerns in potential failure zones can significantly reduce roadside slope disasters in Nepal.

14. Soil Structure Interaction Effect in Foundations

    Khemraj Pokharel, Sushan Prajapati, Kundan Sharma, Unisha Ghimire, Ramesh Karki, Prem Nath Maskey

    Abstract

    A foundation transfers a portion of a structure's weight to the earth. The traditional method of isolated and eccentric footing has been replaced by mat foundation in recent trends. Nevertheless, the concept of soil structure interaction (SSI), which refers to the qualities of the soil in contact with the foundation, has not been implemented in detail in reality. Research has shown that integrating soil structure interaction (SSI) has a major impact on a structure's performance. Winkler's approach was employed in our work to mimic the spring-like foundation soil. This study details how several foundation types, including combined footing, strap footing, and eccentric isolated footing, affect the RC-frame structure's dynamic properties, including base shear, roof displacement, and natural time period. For all foundation types, the SSI impact revealed an increase in the structure's roof displacement; however, the effect is more pronounced in the case of an eccentric isolated foundation. Roof displacement was used as a performance criterion to assess the constructions’ performance. This research analyses changes in base shear, roof displacement, and natural time period as a result of taking SSI into consideration. It ends with a call for SSI to be taken into account in structural analysis and design.

15. Stability Analysis of Gabion Revetment for River Bank Protection Based on Field Investigation

    Suresh Laudari, Tadashi Hara, Hiroshi Nakazawa

    Abstract

    Gabion structures are wire cages or baskets filled with rocks, stacked in rows, and commonly used in Nepal for roadside construction, river flood management, and landslide control. Flood events in Nepal cause significant property damage and loss of life annually, and gabions are highly effective for flood control and riverbank protection. This study conducted field investigation in different gabions such as Japanese gabion practices, and a mixed version combining both methods. The goal was to assess the stability and effectiveness of different gabion types. Findings indicated that while the improved mixed gabion method showed slightly more deformation than the Japanese method, it remained stable under external forces like river flow and earth pressure, making it suitable for riverbank protection in developing countries. The study also emphasized the importance of proper design and installation practices, such as correct base foundation installation, standardized gabion design, launching aprons, and use of geotextiles. These elements are particularly crucial following flood events, as soft foundations and bed scouring can undermine gabion stability. Properly implementing these components can significantly enhance gabion structures’ long-term durability and effectiveness.

16. Pile Tests in Nepal: Current Practice and Enhancements

    Arun Kumar Pandit, Anand Gupta

    Abstract

    Pile foundation is the most common type of foundation adopted for major bridges and buildings. According to the information collected by various researchers and available databases, 90% of the major bridges and high-rise buildings have pile foundation. Bored cast-in-situ reinforced concrete piles are currently in practice in Nepal. Unstable ground conditions, lack for good construction technology and tools, unavailability of experienced construction team, lack of insights and professional ethics, etc. leads to construction of poor pile foundation. Recently, many cases of bridge failures building pile failures have been noticed, in Nepal. Hence, quality control measures during construction of piles along with post-construction quality assurance tests are most essential for the pile foundation and especially for bored cast-in-situ reinforced concrete pile foundation. Pile Integrity Tests can assure the quality of constructed piles and Pile Load Tests can help to verify the load carrying capacity of the piles. This paper emphasizes on the integrity tests available in Nepal and Pile Dynamic Test which has been introduced recently in Nepal and being used in few major highway projects of the nation.

17. Tunnelling for Metro Rail in the Ground Conditions of the Kathmandu Valley-Patan Line (Bhrikutimandap to Satdobato Section)

    Pawan Babu Bastola, Binod Lal Amatya, Abinash Aryal

    Abstract

    Growing traffic calls for a shift from private modes of transport to a sustainable Mass Rapid Transit (MRT) system in the core area of the Kathmandu Valley. A study on tunnelling for the urban rail of the Kathmandu Metro-Patan Line-South section (Bhrikuti Mandap to Satdobato Section) in the ground conditions of the Kathmandu Valley is presented. Underground twin tunnels with in internal diameter of 5.4 m at a tunnel axis depth ranging from 11 to 35 m below ground level are proposed adopting major road alignments wherever feasible. The geometric parameters of the 6.2 km proposed alignment were adopted in accordance with the Standard Urban Railway System for Asia (STRASYA). Based on the archived ground investigation reports, the Earth Pressure Balance (EPB) type of Tunnel Boring Machine (TBM) is found to be most appropriate for the tunnel passing predominantly within the Kalimati Formation of the Valley. Ground movement assessment at the surface due to tunnelling and station box construction is followed by the establishment of 5 and 10 mm settlement contours along the route. Tunnel lining design is performed using a closed-form solution such as the Curtis-Muir Wood Method. A six-segmented precast concrete lining (M40 Concrete grade) of 300 mm thickness is proposed. Such a lining is found adequate for the seismic condition anticipated in the Valley. Major heritage sites along the routes are tabulated to highlight the need for conservation of such sites during metro construction. Spoil generated from the tunnelling activity is estimated to highlight a need for spoil management.

18. Seismic Bearing Capacity Analysis of Skirted Footing on Cohesive-Frictional Soil Slopes

    Neelagiri Vallaba Datta, Sunil Khuntia

    Abstract

    Soil reinforced with the help of skirted footing enhances the bearing capacity of a footing placed on the slope with cohesive-frictional (c-ϕ) soil. The present study investigates to find the seismic bearing capacity (N_cγs) of skirted footing resting on slope with c-ϕ soil using lower bound finite element limit analysis (LB-FELA) and pseudo-static approach. An adaptive meshing provides concentrated finite elements around the skirted footing and gives better results compared to the uniform mesh. While performing the analysis, the present study considers the various parameters like angle of internal friction (ϕ), slope angle (β), cohesion factor (c/γB), depth of the skirt (D/B), and edge distance from the slope crest (e/B) and horizontal seismic coefficient (k_h). This type of analysis provides valuable insights into the behavior of the seismic bearing capacity factor (N_cγs) of a skirted footing resting on slope with c-ϕ soil for various parameters. The stress proximities are generated to understand the yielding nature of a soil under various loading conditions.

19. Integration of Adaptive Design, Construction and Instrumentation for Underground Structure: A Case Study of Surge Tank of Tanahu Hydropower Project, Nepal

    Raja Bhai Shilpakar

    Abstract

    A 3-Dimensional numerical modeling (FLAC^3D) was used to design Surge Tank (ST) (of THP) located in thinly foliated dark gray to black Slates and Phyllitic Slates. ST was oriented, located, designed and constructed as per pre-scribed Method Statement (MS). MS is prepared considering overburden > 250 m, weak & anisotropic rock mass, i.e., susceptible to sliding along foliation planes, and rock mass with weak layers bands, i.e., prone to failure. Due to very weak zone with shear bands encountered during excavation, rigorous exploration/testing was done via. Pilot tunnel and borehole scanning. ST was finally designed (with reduced dia. of 23.5 m) by shifting of 21 m southward based on the test result. Pilot hole drilling (dia. 0.25 m) and reaming (dia. 1.40 m) was conducted by RBM. Then shaft sinking method was implemented to excavate the shaft in 3 radial slices and 4 circumferential parts. ST has been excavated even by mechanical means in the weak rock mass. ST excavation (44,220 m³) was started on 01 Aug 2021 and finished on 21 Nov 2023 along with support measures consisting of pre-consolidation grouting, steel ribs/lattice girder, DCP anchor in addition to rock-bolts & shotcrete. The real-time monitoring data was used for continuous evaluation of underground stability, which enhanced the recursive and diligent design optimization in conjunction with a well-structured/professional MS thereby restrained stability. The integration of adaptive design, a well-defined construction strategy & MS along with continuous instrumentational monitoring and timely responses, has resulted the successful construction of ST.

20. Finite Element Based Design of Unreinforced Unpaved Roads Resting on Deformable Marginal Soil Subgrade

    Nayan Jyoti Sarma, Anu Tamang, Arindam Dey

    Abstract

    Unpaved road comprises around 80 to 85% of global road network, and has to pass over marginalized subgrades in many instances. Traditional design practices of unpaved roads consider the road structure to be in rigid condition with a subgrade layer purely cohesive in nature. The strength characteristics of such subgrade is represented by the undrained cohesion of the subgrade. However, a large portion of Indian unpaved road network rest on marginalized subgrade soil. Under quasi-static vehicular loading condition, it is idealistically assumed that the individual components (aggregate and subgrade) would not undergo failure under the transfer of stress generated by surface loads. However, such design approach results in conservativism that ultimately increases the overall cost of the construction. To overcome these constraints, a finite-element (FE) based study is conducted to model unreinforced unpaved road resting on c-φ soil subjected to a typical combination of axle loads and tire pressures. The study considers the individual failure of the subgrade and aggregate under construction and vehicular load respectively. Step-by-step design philosophy is developed to assess the least shear strength parameters of the individual components required to prevent failure considering coupled stress-deformation effects.

21. Bearing Capacity of Bored Pile Using Semi-analytical and Numerical Modeling

    Amit Kumar Varma, Sanjay Kumar Jha

    Abstract

    Pile foundations are one of the most common types of foundations used for civil engineering structures such as bridges, high-rise buildings, etc. In the case of pile foundations, there are several semi-analytical/empirical relationships proposed to estimate pile tip and skin friction capacities. Different design codes and methods result in a significant difference in pile capacities. So, the pile load test, a reliable but expensive method has to be conducted. However, the number of pile load tests at a site is generally limited. In situations where pile load tests are limited or not performed, numerical methods can be a powerful tool to predict the pile behavior. In this study, a 2-D model of a bored pile with the surrounding soil under a vertical load is simulated in the commercial general finite element software, ABAQUS. The predictive ability of the models is verified by comparing them with data obtained from the pile load test. The numerical results are also compared with semi-empirical correlations available. The results show that the 2-D FEM model of a bored pile is more conservative than the conventional result, but it can be used to simulate the pile load test efficiently. The output of this study will be very useful for the determination of the bearing capacity of axially loaded piles supplementing the semi-analytical approach and avoiding/supplementing expensive pile load test.

22. Review of D Wall Trench Stability for an Underground Metro Shaft Based on Analytical, 2D and 3D Numerical Methods

    V. S. Sowmiyaa, Doraswamy Raju

    Abstract

    To facilitate underground metro excavation Diaphragm Walls (also called as D walls) are generally constructed as a temporary or permanent earth retaining system. After guide wall construction the first stage of D Wall construction involves excavation and simultaneous filling of slurry fluid. Several D Wall trench instability issues are quite common at this stage which may lead to cave in or collapse of D Wall trench. Several analysis methods are available to study this stability mechanism of D Wall trench. The trench parameters such as required slurry height above the ground water table, required slurry unit weight can be estimated by these methods. Also, trench stability can be ensured by determining the factor of safety from these methods. In this current study, the design of D Wall Trench is carried out by analytical and numerical methods. D Wall construction for an underground metro shaft is considered for the study. The shaft is in challenging geological condition such as presence of thick deep clay deposits and high ground water table. The D wall trench design is carried out by various analytical methods and is compared with two dimensional (2D) and three dimensional (3D) finite element methods. Plaxis 2D and Plaxis 3D, finite element-based software, are used for this purpose. Based on the results from both analytical and numerical methods, an optimistic trench parameter such as slurry height and slurry unit weight can be determined which can be compared with field observations.

23. Design and Case Studies of Polymeric Strip Reinforced Soil True Abutment

    P. S. Harshith, Ratnakar Mahajan, Manab Rijal

    Abstract

    Reinforced soil (RS) walls with vertical faced segmental concrete panels as facia element and polymeric strips ParaWeb as soil reinforcement is extensively used globally over the last four decades as an alternative to the conventional concrete retaining walls due to its economy, speed of construction, stability, flexibility, and long-term performance. The first geosynthetic-reinforced soil walls were built in France in 1970 and 1971.The first ever Reinforced Soil (RS) Wall with Paraweb as soil reinforcement in India was constructed in 1988 in Sherpur (Ludhiana) and Phagwara section on National Highway (NH)-1. Also, in Nepal Reinforced Soil (RS) Wall technology with Paraweb™ and concrete panels was first adopted for soil retention works on Bhaktapur road, Katmandu in 2010. Reinforced Soil (RS) Wall technology as bridge abutment (true abutment) supporting the superstructure of the bridges have been used on several bridge projects over the past few decades in foreign countries, but still it is not used extensively in India and Nepal. The usage of Reinforced Soil wall technology for bridge abutment results in saving time and money and help in progress of the developing nations like Nepal. It is also an ecofriendly system as it reduces the carbon footprint. The current paper discusses the concept, components, design methodology along with advantages and case references of true abutments globally which can be adopted for Nepal and India also.

24. Curtain Grouting in the Himalayan Rockmass—The Upper Tamakoshi Dam Case Study, Nepal

    Sanjib Sapkota

    Abstract

    Ensuring stability to the dam foundation of a hydropower plant involves understanding geological conditions, adhering to quality standards, and implementing regular maintenance. The economic performance of the plant depends on both construction and long-term operational costs. Curtain grouting is an effective method for enhancing dam stability by injecting grout to fill voids and fractures, reducing seepage, and increasing the foundation's strength and impermeability. After drilling holes to the designed depth, grouting was conducted in an upward sequence, with intervals of 3–5 m at the maximum pressure of 10 bars. Employing a stage-wise approach, encompassing primary, secondary, and tertiary stages, this study demonstrates a notable reduction in permeability values and a gradual decrease in grout injection rate across successive stages, indicative of a successful intervention. Through this case study, we underscore the significance of targeted grouting techniques in the Himalayan rock masses. The findings offer valuable insights for future dam construction and infrastructure projects in similar geologic contexts, emphasizing the importance of proactive mitigation strategies in ensuring the safety and longevity of critical infrastructure in the Himalayan rock mass.

25. Parametric Optimization of Design Factors for Driven Soil Nail Structure Using Finite Element Method Framework

    R. C. Tiwari, P. K. Jha, N. Chapagain, S. Shrestha, P. Bist, M. Khanal, M. B. Miya, M. Mukhiya, A. Tiwari

    Abstract

    This paper investigates driven soil nail structures for roadside slopes, focusing on parametric analysis. It aims to identify the most influential factors based on the factor of safety (FOS) and permissible slope deformation. This paper optimizes design factors such as face slope, nail inclination, nail length etc., to improve their efficiency and safety. Automation techniques were utilized to manage 38,880 models, facilitating model generation and selection for result analysis. Heuristic-based artificial intelligence algorithms were integrated with a Finite Element Method (FEM) program, reducing the number of models to 17,587. The study also examines the limiting criteria for driven soil nails. Among the simulated models, 1642 failed, with displacement criterion being more critical than FOS criterion. Specifically, 169 models failed both criteria, 344 failed only the FOS criterion, and 1129 failed only the displacement criterion. Additionally, it is found that milder face slope and flat backfill are ideal for fulfilling displacement criterion.

26. Deep Excavation Support in Soft Ground with Parametric Variations for Adjacent Structures

    Madan Puri, Ujjwal Niraula, Bhim Kumar Dahal

    Abstract

    During the construction of a high-rise structure, a deep excavation is required which is subjected to lateral earth pressure from the area surrounding the existing adjacent structures. So, a construction of a cantilever pile wall is necessary to resist and confine this lateral earth pressure. This paper examines cantilever pile walls, an earth support structure to transfer load, minimize deformation, stabilize soil, and maintain structural stability during soft ground excavation. Three distinct foundation conditions—isolated, strip, and mat foundations—are taken into consideration with adjacent structure base load each subjected to loads of 100 and 200 kPa. The focus of this study is the soft soil at the Teku location in the Kathmandu Valley, Nepal, which has an undrained cohesion of 27 kN/m². The study uses finite element analysis and 3D modeling techniques to assess the performance of cantilever piles with diameters ranging from 0.3 to 0.5 m. Numerical modeling is done using Plaxis 3D software for evaluation of the soil-structure interaction. Even though cantilever pile walls and their behavior in different soil conditions have been thoroughly studied, there are still several gaps in our understanding, especially regarding soft ground conditions like those in Kathmandu Valley. There is not enough research incorporating several variables, including supporting pile size, adjacent base loads, and adjacent foundation types. This study makes use of finite element analyses to provide an understanding of the pile wall behavior and deformation of the surrounding soil. The results of this investigation are expected to contribute to the use of efficient support systems for deep excavations in soft ground.

27. A Review on Geothermal Energy Piles—An Alternative Geotechnical Solution for Sustainable Infrastructure

    Sai Venkata Bharath Puppala, Hari Krishna Padavala

    Abstract

    This paper explores the increasing consideration toward geothermal energy piles (GEPs) in the construction industry as an environmentally friendly and economically viable approach for building temperature regulation. The geothermal energy piles leverage stable ground temperatures below shallow depths to function as a heat sink or heat source for ground source heat pump (GSHP) systems. The GSHP system, comprising of a heat pump unit, heat exchanger, and heat transfer pipes, makes these GEPs extract or transfer heat between the ground and the building. This reduces our dependency on conventional cooling and heating methods, thereby minimizing harmful greenhouse gas emissions. This paper delves into the two primary GEP types: driven (displacement) piles and bored (non-displacement) piles. It aims to provide a wide-ranging review of the available literature on the practical application and implementation of GEPs, encompassing their various types, designs, construction methods, benefits, and challenges. Furthermore, the paper summarizes case studies from around the world showcasing the use, advantages, and limitations of GEP implementation. It also compares different types of GEPs to highlight their relative merits. By compiling existing research on GEP foundations, this paper aims to promote the extensive adoption of GEPs as a feasible alternative energy source within the Indian construction industry, fostering a reduction in the sector’s carbon footprint.

28. Numerical Analysis of Highway Embankment Constructed Using a Lightweight Fill: A Case Study

    Vaibhav Vilasrao Butle, G. S. Parvathi, Anirban Mandal, V. Srinivasan

    Abstract

    This study investigates the application of lightweight fill materials, specifically Expanded Polystyrene (EPS) geofoam, in the construction of highway embankments, focusing on the I-15 Reconstruction Project in Utah. Traditional embankment construction methods often face challenges with soft or loose soils, leading to significant settlement issues. Utilizing geofoam addresses these challenges by providing a highly compressive-resistant, lightweight, and easy- to-handle solution, which prevents excessive loading on underlying soils and structures. This paper presents a comprehensive numerical analysis using PLAXIS 2D to model the stress–strain behaviour and settlement characteristics of the geofoam embankment, comparing the results with field measurements and previous studies. The findings indicate that geofoam significantly reduces settlement and maintains long-term stability, although numerical models sometimes underestimate settlement at greater depths due to complex soil-structure interactions not fully captured in simulations. Additionally, the study highlights the importance of accurate subsoil characterization in predicting vertical stresses. Overall, the research supports the viability of EPS geofoam as an effective material for highway embankment construction, offering insights into its practical benefits, limitations, and potential for broader application in infrastructure projects.

29. Effect of Pile Diameter on the Response of Combined Pile Raft Foundation

    Shailja Gupta, V. A. Sawant, P. K. Gupta

    Abstract

    In recent times, there has been a notable increase in the demand of high-rise buildings. Pile raft foundation has been recognized as the most economical and efficient foundation for high-rise buildings. By using pile raft foundations, the risk of sudden collapse in these buildings is also mitigated. Moreover, both total and differential settlement are decreased compared to traditional pile group and unpiled raft foundations. However, in practical designs, the contribution of the raft is often disregarded and the foundation is typically designed solely as a pile foundation. Therefore, the present study aims to determine the CPRF coefficient of a pile raft subjected to axial load. Further parametric study is performed to examine the effect of pile diameter on the response of pile raft. Piles share maximum proportion of axial load. With increase in pile diameter CPRF coefficient of pile increases and that of raft decreases. Also, settlement of pile raft decreases with increase in pile diameter.

30. Numerical Investigation of Suction Profiles Under Cracked Soil Conditions

    Bikash Devkota, Md Rajibul Karim, Md Mizanur Rahman, Hoang Bao Khoi Nguyen, Donald A. Cameron

    Abstract

    The soil’s behavior is significantly affected by the interactions at the soil-atmosphere-vegetation boundary. For some soils, near vertical drying shrinkage cracking is common and can extend to a significant depth. Such cracks influence the overall moisture dynamics between seasons and affect the behavior of soil and structures built on/in them. In areas with expansive soils, moisture change-related ground movement can be magnified due to the presence of cracks. Some examples of vulnerable structures include soil slopes, pavements and lightweight structures like residential building footings, water mains, and sewer lines. Using numerical tools, this study examines the changes in moisture distribution and resulting suction profiles due to the presence of cracks of different geometries and dimensions. The crack geometries were selected based on field observations. A finite element program, SEEP/W was used to simulate the saturated–unsaturated flow behavior. Numerical analyses showed significant changes in suction profiles and as a result ground movement is likely due to the presence of cracks.

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