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Über dieses Buch

This volume comprises select papers presented during the Indian Geotechnical Conference 2018. This volume discusses construction challenges and issues in geotechnical engineering. The contents cover foundation design and analysis, issues related to geotechnical structures, including dams, retaining walls, embankments and pavements, and rock mechanics and construction in rocks and rocky environments. Many of the papers discuss live case studies related to important geotechnical engineering projects worldwide, providing useful insights into the realistic designs and constructions. This volume will be of interest to students, researchers and practitioners alike.

Inhaltsverzeichnis

Frontmatter

Increasing the Yield of Ring Wells by User Friendly Method

Inadequacy of water for the irrigation purposes is being reported as the remarkable problem from the farmers. The groundwater and well systems have to be promoted where the construction of dams, reservoirs, canals, etc. alone can’t serve the farmers. In this study, an attempt has been made to develop to draw water efficiently, to the ring wells situated along the bank of a river. A ring well was selected as the prototype along the river bank and the physical properties of the soil along the periphery of the well were determined to know the soil profile around the well. A model was simulated accordingly and the yield of the model was determined by conducting recuperation tests. Further, perforated laterals of two different lengths were inserted in eight radial directions alternatively at the bottom of the well, and yield was measured for various combinations of the laterals. Similarly, the recuperation tests are conducted even for the slotted laterals and compared with that of the perforated ones. The yield of the model without laterals and with laterals has been compared to know the efficiency of the model. The combination of laterals which gives the optimum yield in the model was selected and provided in the prototype. From the present study, it can be concluded that usage of laterals increases the permeability of the system and thereby increases the yield of the well without the need for increasing the cross section of the well and thus saving valuable time and money.

H. S. Prasanna, S. C. Harshavardhan, A. R. Chaitra, P. K. Pooja, P. Beeresha

Study on the Effect of Soil as a Filler in Foamed Concrete

The problem of concrete waste disposal poses a major challenge to the engineers working in the construction industry. In this scenario, soil can be envisaged as an eco-friendly building material. Soil-based foamed concrete is a novel lightweight construction material consisting of cement, soil, water, and foaming agent. The form of concrete with random air-voids created within the volume by the action of foaming agents is known as foamed concrete. It is characterized by its high flowability, low cement content, low aggregate usage, and excellent thermal insulation. It also possesses characteristics such as high strength-to-weight ratio and low density. Foamed concrete is considered as an economical solution in the fabrication of large-scale lightweight construction materials and components such as structural members, partitions, filling grades, and road embankment infills mainly due to its easy production process from manufacturing plants to final position of the applications. In this paper, the effect of partially replacing conventional cement with two different types of clayey soil is explored and reported. The results indicate that the strength of soil-based foamed concrete satisfies the minimal strength requirement for a building block as per Indian Standards (IS) specifications along with significant improvement of thermal characteristics. Water absorption and density properties are also reported.

K. S. Kavya, K. K. Jithiya, N. Athulya Vijay, Jiji L. Jayan, M. Karthik, Y. Sheela Evangeline, Sajan K. Jose

Effect of Variation of In Situ Moisture Content on Pullout Capacity of Grouted Soil Nail

Soil nailing has traditionally been used as a method to retain soil excavation and to stabilise soil slopes. The effectiveness of this method depends on the pullout resistance of the nail, amongst other factors. There have been instances when the shear resistance between the soil and the nail has deteriorated when the soil volume reduces or when the soil shrinks with the decrease in moisture content. This can happen during the curing period of the cement used in the grouted nails. In the present study, a number of laboratory model tests were conducted in cemented grouted nails installed within silty soils. The variation of pullout resistance with curing period of the cement grout was determined. Spatial variation of the moisture content with depth and distance away from the nail was determined after each pullout test. To support the findings, direct shear tests were performed between the cement grout and the soil at the same moisture content at which pullout tests were conducted. The results indicate a reverse behaviour of the interface friction angle due to the change in moisture content.

Avishek Ghosh, Sayantan Chakraborty, Ashish Juneja

Behavior of Instrumented Piles Under Different Loading and Soil Conditions

A pile is primarily a long container of cylindrical shape having small diameter which is made up of a strong material such as concrete, steel, wood, etc. and is placed or driven into the ground to support the structures or buildings built upon it. With increase in infrastructure development in today’s world, a lot of advanced structures are being constructed globally. But the assurance of success of these structures after construction is still hard to determine. However, nowadays with the advancement in technology in the field of instrumentation, it is possible to validate the performance of the structures periodically. It has been seen several times that the superstructures may need some changes in its architectural or structural patterns. These changes will bring some extra load over the structure, which is not considered by the developers. Hence, to study these changes, instrumentation of the piles is to be done. In the present study, a test pile of 7 cm diameter and 50 cm height was casted and was monitored while carrying out series of compression, uplift, and lateral load tests on different soil conditions. The “load versus settlement curves” as well as “load versus strain curves” were plotted and were compared for different loading and soil conditions. Finally, the amount of the load that would be taken by pile reinforcement and pile material was calculated separately and load transferred through skin friction was obtained.

Anshul Gautam, Satyendra Mittal

Effect of Piles on the Design of Raft Foundation

The combined raft, soil and pile foundation system has reached a high level of familiarity and is now being used to support a large number of structures. When the bearing capacity of the raft foundation is acceptable but the settlement value exceeds the permissible limit, raft-soil system is reinforced with piles to reduce settlement. Here, piles act as settlement reducers to the raft-soil foundation system. Different researchers have studied the effect of varying pile, raft and soil parameters on the settlement response and load-sharing behaviour of the raft and piles in a combined raft, soil and pile foundation system but less attention has been paid to the stress response behaviour of the raft. As this aspect is considered to be important from economics of raft design, a study has been performed to understand the stress response of the raft on the introduction of piles. The stress response of the raft for varying load conditions, Ec/Es ratios, thicknesses of raft and diameters of pile have been studied by performing numerical analyses on the foundation system supporting a moderately loaded 12-storeyed real-time commercial structure located in Chennai, India. An attempt has been made to study the applicability of Equivalent Pier concept. The above analyses were performed for two different layouts of piles. The behaviour of the stress and settlement responses of the raft reinforced with piles was compared with unpiled raft. Staad-Pro V8i and Ansys 16.0 have been used for the study and this paper presents observations and discussions from the study.

L. M. Malavika, V. Balakumar, S. S. Chandrasekaran

Interaction Effect on Laterally Loaded Piles in Cohesionless Deposit

Pile is the only solution to transfer the vertical and lateral loads to deeper strata in high-rise buildings. Here, an attempt has been made on laboratory model single pile and pile groups to investigate lateral resistance of the piles. However, this paper puts up the results of lateral static load tests executed on model steel and wooden single pile and pile groups, in cohesion-less deposit about 1 m deep at varying sand density and length to diameter ratio keeping the spacing constant. Load is applied using turn-buckle and measured by a spring balance. Dial gauges are installed to investigate the average displacement. The effects of embedded length to diameter ratio, sand density, configuration of piles, material of piles and group efficiency are studied and explored. The test results are substantiated theoretically by GEO5 software for both single pile and pile groups considering the properties in aligned with that of experimental studies.

Sachchidanand Kushwaha, Ashok Kumar Khan

Review of Load Test Performance of Base Grouted Concrete Piles

Bangladesh is a low-lying country crisscrossed by many rivers. Large diameter bored piles are replacing caisson foundation in Bangladesh. Bored cast in situ pile is a popular choice for heavy loaded structures due to the ability to adjust the pile length suitably in case of any variation found in the actual geological strata. Geological strata are predominantly silt in nature and N-value in this region is less than 5 up to 15 m depth. Pile design is based on field N-values and laboratory test results. Pile capacities estimated through static formula are in co-relation of N-value and laboratory test results. Two 1.5 m diameter bored cast in situ piles without base grout and two 1.5 m diameter bored cast in situ piles with base grout were casted, and initial load test was performed on these piles to finalize the pile length. This paper presents the vertical load performance of 1.5 m diameter base grouted concrete piles in comparison with ungrouted bored piles.

D. Nagarajan, K. Raja Rajan, T. Vijayakumar

Uplift Capacity of Single-Belled Anchor in Cohesionless Foundation Media

This experimental investigation describes the variation in uplift capacity of single-belled anchors due to embedment ratios of 3, 4 and 5, diameter ratios of 0.28, 0.33, 0.38 and 0.46, and bell angles of 45°, 54°, 63° and 72°. The reason for variation in uplift behaviour is explained by failure diagrams. The uplift capacities show consistently increasing trend due to higher embedment ratios and lesser diameter ratios, and are found to be effective to gain uplift capacities for bell angles of 45°, 54° and 63° compared to 72° belled anchors.

Tanaya Deb, Sujit Kumar Pal

Effect of Footing Shapes and Reinforcement on Bearing Capacity of Three Adjacent Footings

The effect of geogrid reinforcement on bearing capacity was studied on three surface square footings in series. Parameters included under the reinforcement configuration were, length of reinforcement on either side beyond center of footings (Lx), depth of first geogrid layer (u), vertical distance between geogrid layers (h) and center to center distance between three footings (S). Also influence of footing shapes was studied for square, circular and rectangular shape of same cross-sectional area for optimum reinforcement configuration. In order to evaluate these effects, laboratory model tests were conducted at 55% relative density of sand. Bearing capacity of adjacent footings has been observed to be improved by providing geogrid reinforcement layer in the foundation soil under closely spaced footings. It was observed that the reinforcement configurations play a vital role in bearing capacity improvement. It was also observed that bearing capacity of the soil varies with the shape of footings.

S. S. Saraf, S. S. Pusadkar

Analysis of Torpedo Anchors for Mooring Operations

A novel technique of dynamically installing torpedo-shaped anchors is investigated. A vast extent of uncertainties arises in pull-out capacity estimation due to the excessive tilt of a torpedo anchor during free-fall and subsequent embedment into the seafloor. This paper will investigate the issues encountered by the torpedo anchor during the vertical drop, which ultimately reduces the pull-out resistance. The pull-out resistance study offered by torpedo anchors is investigated using a finite element tool, PLAXIS 3D. A series of pull-out tests were conducted with anchors under four different ballast conditions (20, 40, 60 and 80%) with three chosen fin configurations (without fin, 3 fins and 4 fins). The anchors are tested for various inclinations (0°, 2.5°, 5°, 7.5° and 10°) and the effect of torpedo anchor tilt on pull-out resistance is studied, and the allowable range of anchor tilt was recommended. Thus, this study provides the benefit of ideal ballast and fins arrangements.

S. Keerthi Raaj, R. Sundaravadivelu, Nilanjan Saha

Ground Improvement for Foundations of Structures Using Stone Column—Case Study on Road Connectivity to ICTT, Vallarpadam Port in Cochin, Kerala, India

Vallarpadam ICTT Port in the state of Kerala was connected with NH-47 by 17.20 km long four-lane highway. Starting from the junction with NH-47, the first 8.40 km length of the project road was on land area. The rest of the project corridor was routed across reclaimed land and the last part of the road was in island of port area. Deep soft clay deposits were found along the project road. In the land area of project stretch, stone column had been adopted for the foundations of RCC retaining wall and box underpass structure as an alternative to pile foundations. The details of foundation adopted, design involving evaluation of load bearing capacity of stone columns-treated soft ground for the retaining wall and underpass structures, and results of load tests on stone columns are provided here in this paper. Details of machinery used, procedures adopted in the installation of vibratory stone columns, and different field controls adopted to ensure the proper formation of stone columns are presented here.

Avik Kumar Mandal, S. Sailesh, Pradyot Biswas

Combined Piled Raft Foundation (CPRF) System for Polymerization Loop Reactor Structure

The current practice followed in the detailed engineering of foundations for critical industrial structures ignores the contribution of the raft (pile cap) and assumes that the loads are supported entirely by the piles. This approach would result in unduly conservative and uneconomical design where the settlement is reduced smaller than necessary with the use of significantly higher numbers of piles. In a combined piled raft foundation (CPRF), the pile cap provides a significant proportion of the required load capacity with the piles strategically placed to boost the performance of foundation by acting as settlement reducers. The paper presents a detailed step-by-step procedure for the implementation of a CPRF as a cost-effective and technically competent foundation system for a polymerization loop reactor structure which represents a critical component of polymerization plant in the refinery unit. The design process consisted of an initial stage of geotechnical site characterization and computation of required parameters based on the results of soil investigation report prepared for detailed engineering. The structural analysis was then undertaken for various code-prescribed critical load combinations to compute the support reactions for foundation analysis and design. The feasibility and further preliminary assessment of CPRF layout was done using Poulos-Davis-Randolph (PDR) method. The pile numbers, length and locations were then refined using finite element-based geotechnical program, PLAXIS 2D. It was found that the implementation of a CPRF versus a conventional piled only foundation provided the required strength and serviceability performance while delivering a cost saving in the order of 30–50%.

P. Jayarajan, K. M. Kouzer

Bearing Capacity Estimation of Shallow Foundations on Dense Sand Underlain by Loose Sand Strata Using Finite Elements Limit Analysis

In the present paper, a statistical limit analysis was carried out to estimate the bearing capacity of the surface strip and the circular base resting on dense sand under the loose sand layer. The analysis was accompanied by a lower and upper bound limit analysis in combination with finite elements and second-order conic programming (SOCP). In this approach, the Mohr–Coulomb yield criterion was used to model soil behavior. Assuming an associated flow rule, rigorous lower and upper bounds on ultimate bearing capacity are obtained with the use of this technique. Comparisons were made with the available solutions from the literature wherever applicable.

Pragyan Paramita Das, Vishwas N. Khatri

Lateral and Uplift Capacities of Barrette Pile in Sandy Soil

This paper presents the results of analyses of barrette piles. For this purpose models of barrette pile were developed in MIDAS GTS software, which is based on finite element method. Soil model was developed by Mohr–Coulomb and pile as linear elastic model. Various shapes of barrette, with similar cross-section area, viz., 1.5, 3 and 4.5 m2 were considered for analysis and their lateral and uplift capacities were determined for different relative densities of soil. The capacities of barrette piles were compared with those of circular pile with the same cross-section area, and the improvement in lateral and uplift capacities of barrette piles was determined. Results indicate that the barrette piles have higher lateral and uplift capacities and percentage increase is in the range of 100–1300% as compared to circular pile. Also, cruciform shape barrette pile has higher lateral and uplift capacity among other shapes of barrette.

Anju Kumari, S. W. Thakare, A. I. Dhatrak

Analyses of Footing Resting on Confined Layered Sandy Soil

The confinement of soil is one type of technique used for improving bearing capacity of soil and reduces the settlement. This paper presents result of analyses carried out on the effect of soil confinement on the behaviour of circular footing resting on loose, medium dense, dense and layered sand bed subjected to vertical, eccentric, inclined and eccentric-inclined load. The parameter includes the confinement height, diameter and placement of confinement from base of footing, varying depth of layered sand bed. Analyses was carried out in PLAXIS 2D which is based on finite element method. From the analysis, load settlement curves were developed and ultimate bearing capacity was determined for various cases. The optimum values of diameter and height of circular confinement and its placement below the base of footing have been determined for different soil conditions.

Apoorva M. Kulkarni, S. W. Thakare, A. I. Dhatrak

Analyses of Shell Footing in Layered Sandy Soil

Shell footing is economic alternative to long-established plain shallow foundations especially where heavy superstructural loads are to be transmitted to weaker soil. There are many shapes of shell footing such as circular, triangular (inverted and upright), conical, and cylindrical. In this paper, results of shell footing are presented. Models of upright and inverted triangular shell footings were developed in PLAXIS-2D software, which is a finite element-based software. Base to rise ratio (B/d or B/h) of the footing was varied. The results of the analysis were plotted as load settlement curves and ultimate bearing capacity were determined in each case. These were then compared with UBC of flat strip footing with similar conditions. The results indicated that shell footings have higher UBC than that of flat strip footing. The analyses were carried out on loose sand, dense sand, layered sand, reinforced sand bed.

A. I. Dhatrak, P. S. Yaldarkar, S. W. Thakare

Performance of Suction Pile Anchor for Floating Offshore Structures

Offshore structures are huge concrete or steel structure used for extracting the oil and gas from earth’s crust and used for producing renewable energy. The suction pile anchor is connected to the floating structure by mooring line which is attached to the pad-eye position on the side of suction pile anchor to maintain it in position. In this paper, the results of analyses of suction pile anchor in dense sand, medium sand, and clay soil bed are presented. For this purpose model of suction pile anchor was developed in MIDAS GTS 3D software. For a suction pile anchor of a particular dimension, mooring positions and load inclination angle of mooting line were varied. From the analyses, pullout force-displacement curves were developed and pullout capacities of the suction pile anchor were evaluated. Design charts were then developed which gives the length and diameter of suction pile anchors for a given pullout force.

S. W. Thakare, Aparna H. Chavan, A. I. Dhatrak

Image-Based Measurements to Estimate Bearing Capacity of Hollow Driven Piles Under Impact Loading

Hollow driven piles are long, slender columns made of concrete or steel and have a predetermined shape and size. They are installed by driving, jetting, screwing, jacking, vibrating, drilling, and grouting, or a combination of them. When a hollow pile (open-ended) is driven into the ground, a soil plug may develop within the pile during driving, which may prevent or partially restrict additional soil from entering the pile. It is known that the driving resistance and the bearing capacity of open-ended piles are governed largely by this plugging effect. Particle Image Velocimetry (PIV) technique has been adopted to understand pile-soil interaction during the installation of piles and to determine the effect of plugging on load-carrying capacity of piles. Experimental studies have been performed in a steel tank of dimensions 600 mm × 200 mm in plan and 450 mm deep. The top central part of front side of the steel tank is made of perspex sheet to facilitate image capture. Half section hollow aluminum piles modeled using wood’s scaling law is used in the experiments. The infill material is cohesionless sand with different densities and impact load has been applied to drive the piles. Under axisymmetric conditions, the impact load is applied on the pile, and failure pattern at the interface region is captured using a high resolution digital camera that is later analyzed through Geo-PIV software. The number of blows required to drive the pile and rate of plugging induced is measured. The strain contours around pile-soil interface obtained through image analysis clearly indicated the effect of infill on pile driving. Bearing capacity of the hollow pile is estimated using three different methods, viz., IS 2911 (2010) SPT-based formula, American Petroleum Institute (API)’s design criteria, and SPT-based empirical equations proposed from literature. It is seen that SPT-based design method considering the plugging behavior gave a better estimate of bearing capacity values.

G. Sreelakshmi, Asha M. N., Divya Viswanath, Y. N. Yogesh kumar, S. Vinodini

Experimental Analysis and Validation Techniques of Piled-Raft Foundation System

Due to urbanization, the high-rise building has become a common and growing phenomenon in all over the world. If a raft foundation does not meet the design requirement by itself, then the addition of a pile (piled-raft foundation system) may be possible with the raft. In this paper, the design of piled-raft foundation system has been carried out as the approximate assessment of the required number of piles, asses where piles may be required and refine piling requirements on their locations. The design strategies for the design of piles have been shown, and it has been demonstrated with the effective and efficient foundation can be designed by utilizing the significant capacity of pile. These strategies improve both the ultimate load capacity of the pile and settlement or differential settlement of the raft. In this analysis using of pile as settlement reducer and the condition in which the approach may be successful is derived. The characteristic behavior of the piled-raft foundation system has been considered in the effect of number of piles, nature of loading, raft thickness, and effect of load level on settlement. The behavior of piled raft is determined by complex soil-structure interaction effects, and understanding of these effects is useful for the reliable design of such foundations. The study brings out the effects of number of piles, pile length, raft thickness, and pile configurations; along with the soil-structure interaction by mean of the numerical modeling validation is compared with the measured and computed results.

R. Vignesh, M. Muttharam

Prediction of Ultimate Uplift Capacity of Short Piles in Sandy Soils

Short piles which are used for supporting the structural systems need to be checked for uplift capacity. In the present study, an attempt has been made to predict the ultimate uplift capacity of short piles embedded in sandy soils even when the piles are not subjected to uplift forces till their failure loads. A total of eight piles were tested with increasing pull out load increments; however the ultimate uplift capacity of these piles was estimated by the method suggested by modified Mazurkiewicz (1998). Based on these results, a comparative assessment on the ultimate uplift capacity of the piles has been made from the previous studies by Ireland (1975), Das (1983) and Chattopadhyay and Pise (1986) and Shanker et al. (2007). The results of the present study indicate that the ultimate uplift capacity of the piles is in close agreement with the expression proposed by Shanker et al. (2007).

R. M. Thejaswini, L. Govindaraju, V. Devaraj

Experimental Investigation of Piled Raft Foundation Under Combined Vertical, Lateral and Moment Loads

Piled raft foundation is a rational and economical solution for heavy and tall structures which are typically subjected to combined vertical, lateral and moment loadings. The interaction of lateral, vertical and moment load on piled raft foundation has not been well understood due to the complex interaction of raft, soil and piles. Studies on the behaviour of piled raft foundation system under combined vertical (V)-horizontal (H) and moment (M)-vertical (V) are limited. The V-M-H interaction study using model scale test can provide an insight into the failure mechanism of pile raft foundation. Present study is an attempt to investigate the combined interaction of vertical (V), lateral (H) and moment (M) loads on response of a model piled raft foundation system embedded in sandy soil maintaining relative density in the order of 50%. First, the ultimate vertical and lateral load capacity of only raft and piled raft foundation are obtained from load-deformation behaviour of raft and piled raft foundation. In the next phase, combined loading (i.e. V-M-H) test on piled raft system is carried out and horizontal displacement of piled raft foundation system is recorded with respect to gradually applied H or M loading at a uniform rate in presence of constant vertical load. The vertical load test results indicate that the bearing capacity is significantly enhanced due to inclusion of piles to the raft as a settlement reducer. However, the combined interaction of V-M-H loading exhibits significant variation in vertical and horizontal load capacity as well as horizontal displacement and settlement of piled raft system as compared to the response obtained with independent loading.

Diptesh Chanda, Rajib Saha, Sumanta Haldar

Study on Cyclic Pile Load Test of Pile Socketed in Rock

In this study, different data of cyclic pile load test of pile resting and socketed in rock have collected and analysed to compare it with pile in sand for separating skin friction and end bearing. We all know that the transfer of load in different piles takes place differently, friction takes the load in friction piles and end bears in end bearing piles but in rock socketed piles both friction resistance and end bearing act together against the load. The load transfer is also depending on the type of soil in which the piles rest. Cyclic loading on pile is the best method to determine, how much of the total load takes up by the friction and by the point resistance. There already exists one graphical and analytical method to separate the skin friction and end bearing of pile resting on sand. In case of pile socketed in rock or resting on rock, the separation of skin friction and bearing is done with an assumption that rocks are in dense sand condition. The data of cyclic loading of pile in rock are analysed as per the IS method and found to be that the results are erroneous. So a separate method is essential to analyse the pile in rock. Initially a common trend in load versus settlement curve to be finalized for introducing a new method to separate skin friction and end bearing. The introduced new methods are worked out and that shows, graphical method gives almost acceptable results but the analytical method don’t. Further studies are required for clarifying graphical method and to modify the analytical method.

A. P. Sumisha, Arvee Sujil Johnson

Uplift Capacities of Inclined Double-Plate Circular Anchors at Shallow Depths in Sand

Inclined plate anchors are used to resist oblique loads in various civil engineering structures like the transmission towers, sheet pile walls, retaining structures, dams, etc. The use of single-plate anchors has been the interest of study from a long time by many researchers. However, the use of double-plate anchors and studies on the same has hardly been taken up. The present work discusses the uplift capacity of inclined double-plate circular anchors. The uplift capacity of 50 and 100 mm inclined circular plate anchors has been investigated. The double-plate anchors consist of two single plate anchors attached to the same tie rod at a spacing (s) equal to the size of the anchor (d). A comparison has been made between double-plate and single-plate anchors. The study summarizes the pullout load at failure for the anchor plates of different sizes and also presents the load-displacement curves of the various tests.

B. Vidya Tilak, N. K. Samadhiya

Analysis and Design of Pile Foundations for a Sewage Treatment Plant

In the present study, pile foundation underneath a single structural unit of a 90 MLD Sewage treatment plant is considered. The optimum configuration of pile arrangement with respect to number and spacing of piles for constant parameters of embedment depth of pile and subsoil characteristics and varying parameters of diameter of pile, eccentricity of loading, and pile material are investigated by using ETABS and SAFE softwares. The optimization, in terms of axial loads and slab stresses obtained, is considered for piles embedded in stratified soil with lower depths of pile shaft socketed in weathered rock, which has not been studied here to fore. Optimum pile configuration was found to be different than that which was originally provided for the considered structure. Next it was found that the endeavor to analyze pile foundation was justified in the case of provision of lesser number of piles and light-weight structural concrete but not for variation of pile diameter.

S. Samarth, S. Nethravathi, M. S. Nagakumar, G. Venugopal

Analytical and Numerical Analysis of Piled-Raft Foundation of Storage Tank

This paper focuses on the reanalysis of a piled-raft foundation used to support the primary digester of sewage treatment plant under construction in the Southern part of Iraq. Three of the constructed bored piles were failed in the pile test of working piles after applying a load of about 1.5 times the working load. The piled raft is reanalyzed considering the raft contribution. The ultimate carrying capacity of piles and raft settlement is calculated by using analytical equations and numerically by using the software SAFE 12. In order to obtain more accurate values for the required soil parameters, a further soil investigation was carried out, to amend the input data in both analytical and numerical analyses. The results obtained from numerical analysis showed the ability of designed piled raft to carry the working load of the primary digester with an acceptable factor of safety. The analysis results of the piled-raft foundation indicate a change in the load sharing and contribution of the constructed piles due to redistribution of the applied loads on the stiffer piles and the raft.

Mahdi O. Karkush, Ala N. Aljorany

Comparative Study of Methods for Analysis of Laterally Loaded Well Foundation

Well foundation is commonly used in India for road and railway bridges over rivers. It is a massive structure and hence it is generally considered to be safe under laterally loaded condition. Indian Roads Congress Codes (IRC:45-1972 and IRC:78-1983) suggests limit equilibrium approach to determine lateral load capacity of well foundation. It considers well foundation as a rigid body and surrounding soils as elastic in design state and plastic in limit state. Design procedure stated in Indian standard codes determines ultimate lateral load capacity of Well-Soil system. However, it does not yield the magnitude of lateral displacement of a well foundation at the ultimate load. Because of this, it is difficult to decide whether the lateral displacement at estimated ultimate lateral load capacity of a well foundation is allowable or not. Over the years, few methods to analyze the lateral response (both force and displacement responses) of well foundation are developed. These methods consider surrounding soil as linear elastic material which is modeled by linear elastic springs, and well foundation as a rigid body. Recently developed methods consider lateral stiffness as well as rotational stiffness of the surrounding soil and represent soil by parallel combination of lateral linear springs and rotational springs. Some of these methods also consider flexibility of well foundation and model well foundation by Euler-Bernoulli beam element. In this article, we present a comparative study of the available methods of analysis of laterally loaded well foundation. This study indicates significant differences in the response of Well-Soil system obtained from different methods. Validation of existing methods is done with two-dimensional continuum model to identify accuracy in existing models. It highlights the need for proper evaluation of available methods of analysis with realistic incorporation of foundation stiffness and interface effect in modeling the Well-Soil system for pseudo static loading conditions.

Ramyasri Rachamadugu, Gyan Vikash

Influence of Shape of Footing on Coefficient of Elastic Uniform Compression of Soils

Coefficient of elastic uniform compression (Cu) of soil used in design of vibrating bases is generally determined from cyclic plate load test conducted at the site. The value of Cu determined for test plate is correlated to the size of actual footing based on Barkan’s equation. The bases of machines may be square or circular and hence, the values of Cu are required accounting for shape of the footing. The effect of shape of footing on Cu will be different in cohesive and cohesionless soils. So, correlations between Cu values of square and circular footings are required to tackle the different field requirements. In the present study, an attempt is made to correlate the coefficients of elastic uniform compression of square and circular plates of same size in cohesive soils based on cyclic load tests conducted on specimens prepared in CBR moulds. Self straining loading frame is used in the test for application of cyclic loading as it facilitates maintenance of load with settlement, easy loading and unloading of the specimen. Cohesive soils considered in the study are clayey sand and clay of low compressibility. The results of study revealed the ratio of coefficients of elastic uniform compression of circular plate to square plate in cohesive soils under study as 1.2.

C. N. V. Satyanarayana Reddy, S. Swetha

Effective Cut Slope of Rock Slope Along NH-44

Development of national highways in the hilly terrain plays a vital role in the economic development of the country. Landslides or instability of the slopes is more common in the developing hilly terrain due to unscientific cutting of the toe of rock slope for the construction or widening of roads and/or bridges. The NH-44 in the Jaintia Hills district (Meghalaya, India) connecting Malidor to Sonapur (approx. 30 km), have experienced many landslide events causing huge loss of life and property. The two locations along the NH-44 are considered and different cut sections of slopes were studied to support the further extension of the NH-44. Kinematic analysis reveals that the possible type of failures such as wedge failure, planar failure and toppling failure occurs at the selected locations. The stability assessment of in situ rock slope and different cut slope sections were investigated to determine the effective cut slope. Potentially unsafe in situ slopes/different cut slopes were identified using PHASE2, which is a finite element method, based on shear strength reduction technique. The unstable slopes were further stabilized with the installation of shotcrete and bolt. A parametric study has been done to understand the stability of rock slope under various bolting conditions.

Promit Kumar Bhaumik, Rituraj Devrani, Apurba Das, S Sreedeep, S. B. Prasath

Raising of Ash Pond for Augmented Storage

In thermal power plants, a huge amount of ash will be generated as a result of combustion of coal in large quantities. The generated ash will generally be transported and stored in designated areas called ‘ash pond’, before finding use in cement plants or any other engineering purposes. Ash pond is generally formed by creating an earthen embankment all along the identified periphery. In primary phase, the earthen embankment is constructed to contain the ash slurry up to maximum ash fill level, which is termed as ‘starter bund’. In the secondary phase for augmenting the ash storage volume, the ash bund height will be increased by formation of bund of equal heights in stages over and above the starter bund, which is termed as ‘raisings’. This paper covers the raising of bund, construction material, design and construction aspects.

B. V. Sushma

Possible Use of High Draining Material in Core of Earth Dam with Admixtures

In construction of earthen dams, impervious materials are used in the core and pervious materials are placed in the upstream and downstream portion. Most of the construction sites of earthen dam have abundant availability of pervious materials but lacks in the availability of impervious materials. In earthen dams, impervious materials are responsible for the control of seepage loss of the dam. But due to the shortage of impervious materials, there occurs a need to meet the demand of core materials of the dam. To establish the requirement of low permeable soil, it needs to be transported from lower terrain to the construction site at high transportation charge. To minimise the construction cost of the earthen dam, there is a need to upgrade the locally available materials to the desired requirement. This can be achieved by Gradation method or by addition of foreign materials in a small ratio. In the repeated experimental programme, the permeability of locally available soil was reduced by adding industrial and agricultural wastes like fly ash or rice husk ash. Some further experiments have been performed to reduce further permeability by adding various percentages of bentonite mixed with fly ash and rice husk ash.

Saroj Kundu, Pritam Dhar, B. C. Chattopadhyay

Experimental Study on Cantilever Sheet Pile Wall

This paper presents the result of an experimental study conducted for evaluating the effect of depth and distance of adjacent footing on the behaviour of cantilever sheet pile wall. Model sheet pile wall tests have been performed in the medium dense sand. Lateral load on sheet pile wall is obtained by four proving rings attached to the sheet pile wall along with its depth, with the help of four titanium hollow pipes. The lateral load coming onto the sheet pile wall is observed decreasing with increasing depth of footing and distance of footing from the wall face. The position of footing from the sheet pile wall and depth of footing have been varied in this study. The footing is placed at 20, 40, 60 and 80 cm from the wall face at the backfill side with three different depths of footing (at surface, 7.5 cm, 15 cm) in different cases. The effect of sequential excavation has also been presented in this paper.

Aparna, N. K. Samadhiya

Effects of Geogrid and Floating Piles on Performance of Highway Embankment Constructed Over Clayey Soil

In this study, a highway embankment is modeled using 3D finite element package, for a deep medium clay soil site reinforced with piles along with a geogrid layer within the embankment. The pile length, pile spacing, and the geogrid stiffness are then varied. From the numerical analysis, settlement of the embankment surface, foundation surface, and pile cap as well as the lateral deformation of the foundation soil, and embankment toe are computed and compared. The distribution of vertical stresses among the piles and the foundation soil is also determined. The results of the numerical analysis show that inclusion of the piles has a greater influence on reducing the settlement of embankment and foundation surfaces, with the geogrid restricting the lateral deformation at the embankment toe and foundation soil due to enhanced load transfer mechanism.

Dinesh Kumar Verma, Baleshwar Singh

Dynamic Behavior of Retaining Wall Back Paneled by Waste Tire Shredded Rubber Fiber—An Experimental Study

An attempt was made in this paper to use waste tire shredded rubber (WTSR) fiber as a damping material back paneled to the Cantilever Retaining (CR) wall. WTSR fibers placed to absorb seismic-induced thrust on CR wall effectively, thus resulting in reduction of lateral displacement. A series of tests on models of cantilever retaining wall were conducted on uniaxial shaking table. A displacement of 10 mm in z-direction and frequencies of 5, 10, 15, and 20 Hz were selected for all the configurations of fiber panel widths. Four configurations were chosen based on fiber panel width, back to the CR wall which, are 0, 50, 75, and 100 mm. The deflections of the wall, with respect to frequency were measured. It is observed that inclusion of WTSR fiber effectively adsorbed the dynamic trust acting on the CR wall.

Upendra Modalavalasa, Shyam A. Hatiwala, Brijesh K. Agarwal, Swapnali Pawar, Jignesh B. Patel

Suitability of Fly ash in Raising the Embankments

The production of fly ash in India has increased tremendously due to coal-based thermal power plants. The fraction of fly ash re-used for any engineering purposes is merely 0.4–0.5. Hence, the storage and disposal of fly ash is a serious concern. The reserves for fly ash storage were built with specific capacity and needs further expansion for storage. Distinct techniques are available for construction of raising namely inward, outward and central raisings. Although being the most familiar and preferred, the inward raising, being resting on the hardened pond ash and subjected to fresh pond-ash filling, has pertinent stability and seepage concerns. The present study aims at determining safety of existing ash dyke by assessing geometric parameters of dyke, properties of ash and material used for further upraising of dyke. Using computer modelling and simulations, the factor of safety and critical slip surface of the ash dyke at various stages of construction are determined and analysed.

Teja Munaga, Pothula Sai Charan, Mathew Sai Kiran Raju, Lahir Yerra, Bilal Kothakota, Gonavaram Kalyan Kumar

Displacement-Based Analysis of Retaining Wall with Constrained Backfill

In some practical circumstances retaining structure has to stabilise the limited width of backfill which ends with a hillock or a rigid wall. A displacement-based analysis is proposed to analyse a retaining wall with narrow backfill. A retaining wall with backfill that could not mobilise full Rankine’s failure plane due to spatial constraint such geotechnical structure is considered to be a retaining wall with ‘Narrow’ backfill. A finite element modelling followed by plastic analysis is carried out to study such a practical application. Active earth pressure distribution on the wall is presented by prescribing displacement to the wall. It is observed that earth pressure reduces with an increase in the inclination of the rock face with respect to horizontal due to the constraint effect. The critical failure surface for narrow backfill wall is compared with that of an unconfined backfill wall. Results imply that conventional methods of estimation of earth pressure over-estimates in such circumstances.

Godas Srikar, Satyendra Mittal, Sumit Bisht, Ankarapu Sindhuja

Behaviour of Strip Footing Resting on Pretensioned Geogrid-Reinforced Ferrochrome Slag Subgrade

Ferrochrome slag is one of the major industrial wastes produced in huge quantities during the manufacturing of high-carbon ferrochromium alloy and it resembles the coarse dark-colored sand. The use of ferrochrome slag as a substitute for natural soil for major geotechnical projects shall not only mitigate the problems of its disposal but also reduce the problem of environmental degradation. Keeping this in view, a series of model footing tests were conducted with unreinforced ferrochrome slag subgrade, as well as subgrade reinforced with a single layer of geogrid without pretension and pretensioned geogrid. Embedment depth for the geogrid was varied corresponding to the width of the footing for both the cases. For pretensioned geogrid, pretensions in the geogrid were varied as 1, 2, and 3% of tensile strength of geogrid. It is concluded that pretensioning of the geogrid is quite beneficial in enhancing the reinforcement efficiency.

Atul Kumar, Anil Kumar Choudhary, Sanjay Kumar Shukla

Dynamic Response of Tall Chimneys on Pile–Raft Foundation Subjected to Wind Load

Tall and slender structures like chimney and towers are used generally in the power plants and telecommunication industry, respectively. For such structures with extreme heights and dynamic performance, the effect of wind load will have an important role in the design. The present paper evaluates the effect of deterministic wind load on the dynamic response of chimney. For depicting the restraint conditions of the structure in a realistic manner, soil flexibility (soil–structure interaction effect) has been considered while performing the analysis. For the wind analysis, along-wind effect has been considered. This paper explores the chimney considering nonlinear Soil–Structure Interaction (SSI) effects using Beam-On-Nonlinear-Winkler-Foundation (BNWF) approach. A 220-m-high RCC chimney of truncated hollow cone shape has been taken from the case study. The chimney is supported by a pile–raft foundation consisting of 332 bored cast in situ piles on a clayey silt deposit. The chimney has been assumed to be located in open terrain and subjected to a maximum wind speed of 50 m/s. The along-wind loads were computed according to IS: 875(Part 3) and applied along with the height of the chimney. Two-dimensional finite element (FEM) analysis is performed using OpenSees based on the direct method of SSI. Theoretical evaluation of the response considering beam elements for the chimney, pile, pile cap, and spring elements for SSI has also been a part of the study. Displacement responses of the chimney have been considered with both fixed base and flexible base conditions. The study demonstrates the influence and need for consideration of SSI which will properly estimate the response of a structure.

L. Lakshmi, Monu Lal Burnwal, Samit Ray Chaudhuri, Prishati Raychowdhury

Construction Dewatering for Underground Station in Urban Environment

Metro is seen as the only solution for mass rapid transit system in the urban areas. For an underground metro station, deep excavations in densely populated areas impose specific challenges to the contractor. Based on the type of soil or rock, excavation procedure, method, and time shall be adopted. The control of groundwater is one of the most common and complicated problems encountered on a deep excavation. The contractor selects the dewatering method, and the contractor is solely responsible for its design and operation. Many dewatering techniques like multiple wells, sump pumps, vacuum pumps, and deep wells are available to control groundwater. In this paper, the author explains the usage of MODFLOW software for dewatering analysis in the underground metro station and also about the dewatering system which has been adopted in the site. Pump out test is an accurate method of determining the safe yield of the well and also for assessing the actual site condition.

K. Raja Rajan, D. Nagarajan, T. Vijayakumar

Investigations On the Impact of Sub-Structures on Groundwater Flow

Underground structures act as impervious obstacles and modify the groundwater flow pattern. Such structures below the groundwater table affect the hydrodynamic parameters of the aquifers and they disturb the mass balance of the flow system. The main adverse effects change in groundwater level, flow path, and flow velocity. The altered flow velocity leads to re-arrangement of soil particles and variation in the groundwater table. The effect of pile foundations on the groundwater flow pattern was investigated. Numerical simulations using the finite element method were undertaken to this effect. Using the data from the laboratory tests, the finite element model was validated. With the validated finite element model, the influence of various participating parameters was studied. Remedial measures to mitigate the effect of underground structures on the groundwater flow pattern are suggested.

Rohitha P. Kamath, N. Unnikrishnan

Application of Jet Grouting for Geotechnical Challenges

Jet grouting employs the injection of a controlled amount of cement grout into the required volume of soil mass to improve the in situ ground. This ground improvement technique is applied for foundation modification and restoration works such as for waterproofing of dam foundations, confinement for excavations, underpinning of foundations, limiting subsidence over tunnels, etc. This technique can help improve the soil to support foundation loads with minimal settlement and function as excavation support or serve as both foundation and excavation support in a single operation. Such dual capability of the system increases the economic viability by saving time and cost. This paper briefly explains the limitations of various ground improvement methods, the applicability of jet grouting for various geotechnical engineering challenges, the importance of a field quality plan to achieve required design aspects. Case studies are presented that demonstrate the versatility of this emerging technology and its value as a cost-effective ground treatment tool.

Akhila Manne, P. V. S. R. Prasad, Madan Kumar Annam

Optimal Foundation Solution for Residential Projects

Ground improvement is an optimal foundation solution, especially for weak soils and it can be used as an alternative to complement deep foundations such as conventional piling methods. This paper presents a case history of a housing project located in Chennai, India, wherein the project site consists of soft silty clays underlain by loose to medium dense silty sands. To provide housing for the socio-economically poor, the owner decided to optimize the foundation cost. Ground improvement using vibro stone columns, dry bottom feed method was chosen to be the optimal solution and the solution saves construction time too. This technique helped to increase the bearing capacity and to reduce the total settlements and differential settlements within the acceptable limits. Various aspects of sub-soil conditions, design aspects, construction methodology, and quality control measures are discussed in detail, in this paper.

B. Vani, Madan Kumar Annam

Reanalysis of Failure of Soil-Nailed Shoring System and Remedial Measures

Support systems in urban areas for temporary excavations are necessary to keep the sides of excavation nearly vertical, to minimize the excavation area and to ensure that the excavation is stable from stability as well as deformation criteria and will not lead to any damages in the surrounding area. In the present study, the paper discusses the cause for the failure of excavation of 11.65 m deep supported by nailing. The serviceability requirements and factors of safety are evaluated using finite element analysis. Further, it discusses the revised design for a temporary support system. The paper highlights the importance of pull out tests in the preliminary stage as well as during execution which are useful in design and performance assessment of the shoring system. The revised system is implemented in the field and is performing well.

S. Vibha, S. P. Srinivas, G. L. Sivakumar Babu

Determination of Compacted Dense Sand Layer Thickness on Loose Sand Using Odemark’s Method for Design of Shallow Foundation

Bearing capacity of loose sand can be improved by replacing the soil with a suitable thickness of dense sand layer for laying shallow foundations. Present paper deals with a methodology for calculating the optimum depth of such compacted dense sand required for strip footing. In this paper, load on the foundation has been considered to act on a two-layered system. Primarily an imaginary depth of homogeneous loose sand has been determined at which its bearing capacity becomes equal to the vertical stress developed at the same depth using Terzaghi’s theory and stress dispersion approach. The depth of loose sand thus obtained has been transformed into a two-layered system using Odemark’s method to determine the thickness of the dense sand layer. It has been found that such depth of dense sand bed increases with the increase in foundation load and footing width but reduces with an increase in friction angle of the top layer.

Partha Pratim Biswas, Manoj Kumar Sahis, Agnimitra Sengupta

Reliability Analysis on Fatigue and Rutting Failures of Flexible Pavement with the Variation of Surrounding Atmospheric Condition and Mix Design of Bitumen

Reliability is defined as the probability that the pavement’s traffic load capacity exceeds the cumulative traffic loading on the pavement during a selected design life. Fatigue and rutting in flexible pavement are serious mode of failure in high-temperature areas including India and may lead to early failure in pavement. Performance of pavement depends upon various factors such as subgrade support, pavement composition and its thickness, traffic loading and environmental factors. So it is evident that reliability is very much affected by variation of selected temperature range which is shown in this study. The fatigue life decreases with the increase of temperature. It is noticed that slight changes in volume of air voids and volume of bitumen have huge influence on the fatigue life. Temperature variation also affect the rutting life significantly which is well proved in this study. The probability of exceeding the design value is determined and this Reliability is plotted with some parameters.

Sourav Mitra, Saurav Pal, Pritam Aitch

Application of Under Sleeper Pads to Enhance the Sleeper-Ballast Interface Behaviors

Railway industries are facing greater technical and economic challenges to increase the train speeds and hauling capacity of the trains to cope up with the growing population and increasing traffic problems. However, increasing dynamic stresses from the passage of faster and heavy haul trains progressively degrades the ballast layer and other track substructure layers which inevitably leads to excessive settlement and track instability. Nowadays, heavier concrete sleepers used in most of the ballasted tracks are subjected to even greater stresses and faster deterioration. Under Sleeper Pads (USPs) are resilient pads installed at the bottom face of concrete sleepers to increase the degree of vertical elasticity in the track structure and also with the intention of enhancing sleeper–ballast interaction to minimize dynamic stresses and subsequent track deterioration. In this study, cyclic loads from fast and heavy haul trains have been simulated using a large-scale Process Simulation Prismoidal Triaxial Apparatus (PSPTA) to investigate the performance of ballast improved by the USPs. The laboratory results indicate that the inclusion of USP at the harder interface of concrete sleeper-ballast significantly curtails the stresses transmitted and minimizes the amount of plastic deformation and degradation of ballast.

Sinniah K. Navaratnarajah, Buddhima Indraratna

Strengthening of Weak Subgrade Using Geocell

Infra structure projects require bulk quantities of construction materials to build and maintain. Use of locally available materials, which possesses very low shear strength and stiffness, suffers premature failure. Use of inferior quality of materials, in the base and sub base causes excessive lateral spreading that leads to severe distress and costly maintenance. Researchers are in search of alternative materials in order to minimize the construction cost and maintenance cost. Present work focuses on the behavior of flexible pavement reinforced with and without Geocell. Geocell is cellular confinement system made from a polymer material that enhances the stiffness of layer when it is encased. The effectiveness of a Geocell when it is used to reinforce conventional flexible pavements depends on several factors such as thickness of the Geocell, infill material, and placement depth. Reinforced flexible pavement is designed as per the IRC 37-2012 standards. Further influence of geocell is studied by placing geocell at different levels of pavement. Parameters like maximum principal stress developed, distribution, and propagation of stress through subgrade layers, deformation of layers, and maximum deformation of pavement under vehicle load are compared for both reinforced and unreinforced flexible pavement.

G. Sridevi, G. Sudarshan, A. Shivaraj

Stresses Induced on Existing Pipeline Due to Laying of New Pipeline

In recent times, increasing demand for energy has led to rapid development of subsea and offshore assets for oil and gas transportation. Cross-country pipelines are laid to connect and transport hydrocarbons from different source stations to its consumers across the countries. Case study of a new subsea pipeline proposed to be laid on seabed and routed through cross existing pipelines is discussed in this paper. Numerical modeling using Finite Element Analysis (FEA) is carried out to analyze present stress level on existing pipelines, i.e., stress due to backfill and increment in vertical stresses in the soil just above the existing pipeline due to proposed new pipeline. Different pipeline loading conditions along with methodology and assumptions of static analysis are presented. Maximum vertical stress in the soil at the top of existing pipelines due to laying of proposed pipeline is computed. These induced stresses are also compared with the initial stresses on the existing pipeline.

Seema Gurnani, Altaf Usmani, Charanjit Singh

Some Studies on Pavements on Flyash-Stabilized Expansive Subgrades

Construction of roads over expansive soils is associated with huge construction and maintenance costs. Stabilization of such subgrades with flyash is a cost-effective alternative to replacing the expansive subgrade with good quality borrow materials. Performance of stabilized pavements can be assessed and predicted on the basis of laboratory tests, full-scale field tests and numerical analyses. Numerical studies can simulate field and laboratory tests at very minimal costs and within a short duration. Hence, numerical analysis can be used for parametric studies to optimize the thickness of the stabilized subgrade. Engineering parameters of the untreated and treated expansive subgrade were found in a laboratory program. Static and dynamic analysis of axisymmetric models of pavement was conducted using Plaxis-2D. Improvement in parameters like vertical strain at top of subgrade and vertical displacement at top of pavement was found. The thickness of the granular layer and the treated subgrade layer was varied. The static analysis indicates that with the stabilization of the top 0.5 and 1.0 m thickness of subgrade layer, the design life of the pavement can be increased by 4–6 times and 30–70 times, respectively.

D. Nigade-Saha Sanjivani, B. V. S. Viswanadham

Comparison of Geostatistical Technique to Assess the Safe Zones of Water Storage

The quality of water leaching through chemically contaminated soil has affected underground storage. This study aims to find the region of permissible groundwater quality for domestic purposes existing near landfill. This was done by using ArcGIS, and different interpolation methods were used to know the area lying under permissible standards of water usage. It was found that for year 2014 IDW was the best spatial interpolation method, while for 2016 RBF was best with least Root Mean Square error (RMSE) and high value of coefficient of determination (R2). The results of the analysis were helpful in identifying safe zone of groundwater storage and also show that sampling locations are under tidal effect. While assessing zones, it has been found that certain zone has exceeded concentration compared to previous year. This may be attributed to leachate percolation or mixing of high TDS water.

Sunayana, Vikas Kumar, Komal Kalawapudi

Pullout Capacity of Ground Anchors in Non-homogeneous Cohesive–Frictional Soil

Anchors are widely applied as the foundation of structures where significant pullout load is expected. Among various kinds of anchors, plate anchors are frequently employed in practice. The vast majority of the previous works have focused on the pullout capacity of the plate anchors either in undrained homogeneous and non-homogeneous clay or in drained homogeneous sand. The present work has studied the holding capacity of a horizontal anchor plate, subjected to pure vertical pull in homogeneous as well as non-homogeneous cohesive–frictional soil for different combinations of (i) normalized cohesion (c0/γB), (ii) soil frictional angle (ϕ), and (iii) normalized increment factor of cohesion below ground level (rc), where c0 represents the cohesion of soil at the ground level, γ represents the soil unit weight, and B represents the width of the plate. The vertical pullout load (Qu) of the horizontal strip anchor plate is computed using lower bound limit analysis, in conjunction with finite element discretization. The results have been exhibited in a non-dimensional form as Qu/c0B. It has been observed that the non-dimensional pullout capacity (Qu/c0B) increases almost linearly with H/B as long as the measure of ϕ is low; whereas, in case of larger values of ϕ, the increment is non-linear. In addition, the non-dimensional pullout capacity Qu/c0B has been observed to increase considerably with an increment in rc. Although lower bound limit analysis is appropriate for associated flow rule materials, the present analysis has been extended considering non-associated flow rule materials for a few cases by utilizing reduced shear strength parameters. The non-dimensional pullout capacity has been observed to reduce slightly in the case of non-associated flow rule materials, especially for higher values of ϕ. Since the lower bound limit analysis gives the conservative estimation of the ultimate load; therefore, the results computed in this analysis can be used safely for the designing purpose.

Soumya Sadhukhan, Paramita Bhattacharya

Settlement Analysis of Single Circular Hollow Pile

Piles are designed to transfer a load of superstructure to the deep hard soil strata crossing the upper weaker strata through frictional or end bearing action. Settlement analyses for single or group of the solid pile are available in literature based on analytical or empirical approaches. The present study deals with the settlement analysis of single circular hollow and single conventional pile using Plaxis-3D foundation. Effect of diameter, length and position of hollow portion filled with different granular materials of moduli of elasticity is evaluated and studied in terms of the load settlement curve. Results of floating conventional circular pile and floating circular hollow pile are compared in terms of parameters as mentioned above by keeping the same conditions and properties of surrounding soil and pile. Floating circular hollow pile gives optimum and economical results as compared to the single circular conventional pile in respect of settlement up to a certain percentage of varying hollow portion.

Ravikant S. Sathe, Jitendra Kumar Sharma, Bharat P. Suneja

Effect of Excavation on the Settlement of Adjacent Structures

The requirement of increased infrastructure and limitation of space due to urbanization has resulted in the use of subsurface structures to meet the demands. There are many challenges in performing construction activities such as excavation adjacent to existing buildings and settlement is perhaps the most challenging among them. This paper studies the effect of excavation adjacent to existing buildings in the Delhi region for DMRC site carried out by CSIR—Central Building Research Institute. The excavation was carried out for a shaft opening of size 20 m × 20 m and the depth of excavation was around 18 m. The offset distance from the adjacent buildings varied from 4 to 15 m. The analysis was carried out using PLAXIS 3D software. The actual soil data of the site with realistic loadings of the buildings were considered. The results revealed that the settlement of the existing buildings doubled due to the adjacent construction activity as compared to the case of static load due to buildings. Post-excavation settlement was found to be more than the permissible limit indicating the need for improvement measures to be undertaken to minimize the damage to existing structures.

M. S. Aswathy, Achal Mittal, Sidharth Behera

Full-Scale Load Test on Bored Cast in situ Piles—A Case Study

This paper presents a case study on two full-scale pile load tests on the bored cast in situ piles of 800 mm diameter having 10 m length. These piles are intended to be used as foundations for a 20-storeyed residential building in Mumbai. For determining the allowable load carrying capacity of piles, it was decided to carry out initial load tests and gain insight on the behaviour of piles. Further, to verify conformity with the design load obtained from static calculations. A novel method of loading the piles has been used and introduced, as conventional static pile load testing methods require enormous temporary infrastructure for applying larger loads. In this method, a reaction system has been used that derives reaction from the rock anchors using a hydraulic jack to impose the 2–2.5 times the design load on test piles. In this paper, the reaction method was described along with the design of rock anchors. This paper presents a method to predict a safe load from the pile load test data for adopting in the design.

B. V. S. Viswanadham, Pankaj Kumar

Review of Historic Forensic Geotechnical Engineering

We need to preserve our ancient but fast disappearing culture through its structures and substructures. For instance, the ancient people notably built seismic-resistant footings and foundations as well as structures of the earth. In ancient India, engineers had already incorporated many important geotechnical techniques in embankment building as are still observed in the Bunds seen in Goa. Conservation poses an important engineering challenge. Historic Forensic Geotechnical Engineering studies play a vital role in such preservation of traditional architecture. This paper examines various types of Forensic Geotechnical Research and the rationale for further research of historic geotechnical substructures and superstructures and their building techniques and variability. It attempts to overview these important architectural remains and the need for actions. This paper explores the need to study Historic Geotechnical Structures as an important sub-branch of Forensic Geotechnical Engineering Studies by forensic review of different ancient Geotechnical structures and the possibility of making it part of mainstream studies.

Leonardo Souza, Purnanand Savoikar

Machine-Induced Vibration Isolation Using Geocell Reinforcement

The present study aims to investigate the vibration isolation efficacy of the geocell reinforcement through the numerical simulation technique. The explicit finite difference package, FLAC3D was chosen for the dynamic simulations. Initially, the developed numerical models were validated with the results of the vertical mode block resonance test. The behaviour of soil bed and concrete footing was simulated using Mohr–Coulomb and linear elastic models, respectively. The geocell was modelled using two techniques, namely Equivalent Composite Approach (ECA) and Honeycomb-Shaped Approach (HSA). The results revealed that the use of the geocells reduce the resonant displacement amplitude by 56% and increase the natural frequency of the soil–foundation system by 42% as compared to the unreinforced bed. As compared to the experimental results, the ECA modelling technique was found to overestimate the improvement in resonant frequency and the reduction in displacement amplitude by 4% and 10%, respectively, in the presence of geocells.

K. N. Ujjawal, A. Hegde
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