Faculty Publications
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Item Numerical Study on Interference of Surface Strip Footings Resting on Stiff Clay(Springer Science and Business Media Deutschland GmbH, 2020) Hridya, P.; Anaswara, S.; Shivashankar, R.In the present study, the interference effects of two closely spaced strip footings on the surface of stiff clay were investigated. The effect of interference on characteristic behaviour like bearing pressure, settlement and tilt is observed using two-dimensional plane strain analysis. Finite element analysis software PLAXIS 2D is used for this. The behaviour of individual footing on stiff clay is first established. Parametric study is done by varying the width of footing and the spacing between the footings. The results are presented in terms of efficiency factors, which are defined as the ratio of settlement or bearing pressure of interfering footing to that of the isolated footing. The effect of interference is particularly noticeable in terms of settlement. Maximum settlement and tilt occur at a spacing 1.5B irrespective of the footing width. Effect of shear keys placed beneath the footings at different locations beneath the footing and the interference of such footings were also studied. It is found that the presence of shear keys has a significant effect on the interference between the footings, compared to without the shear keys. © 2020, Springer Nature Singapore Pte Ltd.Item A Numerical Study on Interference Effects of Closely Spaced Strip Footings on Cohesionless Soils(Springer Science and Business Media Deutschland GmbH, 2021) Anaswara, S.; Shivashankar, R.Foundations of buildings often need to be placed at close spacings to meet the various structural or functional requirements. In such cases, the combined action of adjacent footings is different from that of a single foundation. The combined effect causes interference of the stress zones. Numerical analysis is carried out on two closely spaced strip footings on sands, by varying the affecting parameters, to study the interference effects. Interference effects are analysed in terms of bearing pressure, settlement and tilt of foundations. In this study, the interference effects of closely spaced strip footings on the surface of cohesionless soils are being investigated. Parametric studies are done for two foundations by varying the clear spacing between the foundations. The results are presented in terms of interference factors. New structures near to the old construction may alter the settlement, pressure and rotational characteristics of the old footing and could lead to its distress. Above all, the load-carrying capacity of the new foundation will be very different from what it would have carried if it were independent—without the interference of the other footing. First footing representing an already existing footing is loaded with half of the estimated failure load of single independent strip footing and second adjacent footing loaded up to failure. The effect of interference of the old foundation is observed to be particularly significant in terms of the settlement and tilt. © 2021, Springer Nature Singapore Pte Ltd.Item Comparative Study of Settlement Performance of Stone Column and Vertical Drains: A Review(Springer Science and Business Media Deutschland GmbH, 2025) Kapile, P.; Sridhar, G.The process of building stone columns through weak soils, specifically soft and ultra-soft clays, is known as “vibro replacement.†An integrated foundation support system with reduced compressibility and enhanced load bearing capacity is formed by the stone column and the intervening soil. Stone columns in cohesive soils easily discharge excess pore water pressure, causing settlement to occur more rapidly than in clay without stone columns. Literature has shown that stone column has the tendency to bulge due to less in-situ lateral stress of soil which results in reduced effectiveness and increased settlement of stone column. Surcharging, a prevalent preloading method for strengthening weak ground, involves applying additional load through soil embankments. In the context of ground improvement, surcharge preloading is commonly used. Prefabricated vertical drains play a crucial role in expediting the consolidation process of soft clay deposits when employing preloading as a ground improvement technique. This paper presents a critical review of the settlement performance of stone column and preloading with prefabricated vertical drains as it is of utmost importance in ground improvement works. A case study comparing the settlement performance of stone column and preloading with prefabricated vertical drains revealed that latter technique is more suitable for extremely soft soil. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item A Review on the Design, Applications and Numerical Modeling of Geocell Reinforced Soil(Springer Science and Business Media Deutschland GmbH, 2021) Vibhoosha, M.P.; Bhasi, A.; Nayak, S.For improving the stability and load carrying capacity of weak subgrade, strengthening methods are to be followed in the field. Among the various approaches, geocells have been identified as an effective soil reinforcement technique for improving soft subgrade behaviour. The three-dimensional honeycomb structure of geocell offers more lateral confinement to the infill soil resulting in improved load carrying capacity. This led to the widespread use of geocells for different geotechnical applications like pavements, foundations, embankments, slope protection, erosion control etc. Many researchers in the past have confirmed the suitability of geocell reinforcement through their experimental, numerical and field studies. In this paper, a comprehensive review of the reinforcement mechanisms, design aspect and numerical modelling techniques of geocell reinforced soil is provided. In addition, this paper highlights the various field application scenarios where different types of geocells have been used and explores the research challenges and scope for further research in this field. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item 3-dimensional numerical modelling of sand bed reinforced with 3D geogrids of triangular form(Australian Geomechanics Society, 2019) Makkar, F.M.; Sreya, M.V.; Chandrakaran, S.; Sankar, N.In this paper, the bearing capacity improvement of a square footing resting on sand bed reinforced with 3D geogrids of triangular form is numerically studied with the help of Plaxis 3D software. The performance of 3D geogrid reinforced sand is also compared with planar geogrid reinforced sand to understand its effectiveness. In the numerical modelling, the soil behaviour is simulated by linear elastic-perfectly plastic Mohr-Coulomb model. The 3Dgeogrid and planar geogrid is modelled using geogrid structural elements available in the software. The model was validated with the experimental results and found to be in fairly good agreement with each other. The effect of various parameters on the behaviour of reinforced soil system was also investigated. It was found that the bearing capacity of multilayered planar geogrid reinforced sand bed improved by 3.68 times, while, the 3D geogrid reinforced sand bed shows 6.8 times improvement compared to the unreinforced sand bed. © 2019 Australian Geomechanics Society. All rights reserved.Item Comparative study on bearing capacity of bottom ash-stabilized soil mixed with natural and synthetic fibers(ASTM International service@astm.org, 2020) Prasannan, S.; Kolathayar, S.; Sharma, A.K.This article assesses the strength behavior of bottom ash (BA)-stabilized soil mixed with different fibers through a series of laboratory tests. Optimum BA and fiber percentage were obtained by small scale lab tests like compaction tests and unconfined compressive strength (UCS) tests. From compaction tests with varying proportions of BA (10, 20, 30, and 40 %), the optimum BA content was found to be 30 %. With this optimum BA content, UCS tests were conducted on soil-BA mix with different fibers (coir, areca, sisal, and polyvinyl alcohol) at various percentages (0.5, 1, 1.5, and 2 %) to find the optimum fiber content. A set of model footing tests were done to check the credibility of using fibers as a strengthening material beneath footing to upgrade the engineering properties of soil to make a reasonable subsoil for the foundation. A total of six model footing tests were performed on raw soil, on soil with optimum BA content, and on BA-stabilized soil mixed with different fibers in their optimum percentage (1.5 %). The bearing capacity of unstabilized unreinforced soil was found to increase significantly with the inclusion of fibers. © © 2020 by ASTM InternationalItem Performance of Footing on Clay Bed Reinforced with Coir Cell Networks(American Society of Civil Engineers (ASCE) onlinejls@asce.org 1801 Alexander Bell DriveGEO Reston VA 20191 Alabama, 2020) Kolathayar, S.; Narasimhan, S.; Kamaludeen, R.; Sitharam, T.G.Geocells are three-dimensional polymeric hexagonal pockets that provide lateral confinement to the soil, thereby increasing the bearing capacity of the soil bed. This paper briefly reviews past studies on geocell reinforcement of soil and presents a new product, cells made out of natural coir fiber, as an alternative to commercially available high-density polyethylene (HDPE) geocells. A series of model plate load tests were conducted on unreinforced soil and on soil reinforced with coir geocells to understand the soil reinforcement mechanism. It was observed that with the introduction of coir geocells, the load-bearing capacity of the soil bed increased up to three times and a significant reduction in the settlement was observed in the underlying weak soil bed. The study also presents a comparative performance evaluation of the natural coir cell-reinforced soil with conventional HDPE geocell-reinforced soil. Further, this paper analytically demonstrates the influence of the lateral resistance effect and vertical load dispersion effect incorporated by coir cells in strengthening the soil bed. © 2020 American Society of Civil Engineers.Item Study on Behaviour of Two Adjacent Strip Footings on Granular Bed Overlying Clay with a Void(Springer, 2020) Anaswara, S.; Shivashankar, R.This paper numerically examines the behaviour of two adjacent strip footings on granular bed over weak soil having a void. Voids could be formed in weak soil strata due to various reasons such as due to water leakage from the water supplying lines or sewer lines, poor drainage and erosion of soil, animal burrows, etc. A parametric study is carried out to understand the influence of granular bed thickness, width of footings, spacing between the footings, and the presence of a void beneath the footing in the weak soil, on the behaviour of footings. To understand the failure mechanism, shear strain contours, for different cases, are being studied. It is observed that there is a certain critical spacing between the two adjacent footings at which the footing/s carry the maximum load. This critical spacing depends on the type of loading, whether equal and simultaneous loading or unequal and sequential loading. The presence of voids also affects the performance of footings. Such voids tend to reduce the load carrying capacity of the footing/s and alter failure pattern. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.Item Interference Studies of Adjacent Strip Footings on Unreinforced and Reinforced Sands(Springer, 2020) Anaswara, S.; Lakshmy, G.S.; Shivashankar, R.Interference effects of two and three strip footings placed adjacent to each other on unreinforced and reinforced sands are being studied in this paper. Effects on stresses in foundation soil, bearing capacity, settlements and tilts of footings are being looked into. Parameters varied in this study are (i) the number of footings (In the case of two footings loaded simultaneously, both experimental and numerical studies are conducted. In the case of two footings loaded sequentially and three footings, numerical studies are done.), (ii) loading conditions, (iii) clear spacing between the footings and (iv) number of reinforcement layers in foundation soil. With two footings, two loading conditions are considered. In the first loading condition, both footings are loaded simultaneously up to failure. In the second loading condition, one of the footings representing an already existing foundation is loaded with half of the estimated failure load of single strip footing and adjacent footing loaded up to failure. With two adjacent strip footings on unreinforced and reinforced sands, both loaded simultaneously, some laboratory-scale experimental studies are also conducted to compare with the numerical results. It is observed that there is a certain critical spacing at which the footing/s carry the maximum load. This critical spacing depends on the loading condition. Reinforcements in the foundation soil used are in the form of hexagonal wire meshes. The effect of providing the reinforcements in layers in the foundation soil is seen in the increased bearing capacity, reduced settlements and reduced tilts of the footings under simultaneous loading condition. Tilts are also found to be influenced by the loading condition. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.Item Model Footing Tests and Analytical Studies on Clayey Soil Bed Reinforced with Coconut Shell Mat(Springer Science and Business Media Deutschland GmbH, 2022) Kolathayar, S.; Gadekari, R.S.The cellular confinement systems are becoming popular in ground improvement because of their efficiency in improving the bearing capacity of soil due to the lateral confinement effect. The commercially available geocells are made from polymer materials and they are costly. This study presents the performance evaluation of coconut shell mat as a cellular confinement system in clayey soil. It is the first of its kind application of coconut shells for soil reinforcement through a lateral confinement mechanism. This soil reinforcement system using coconut shells is termed “Geococoshell” by the authors. A series of model plate load tests were conducted on unreinforced soil, soil reinforced with High-Density Polyethylene (HDPE) geocells, and soil reinforced with coconut shell mats to evaluate the performance of coconut shell mat reinforced soil bed. The results of the experiments showed that coconut shells reinforced clayey soil improved bearing capacity up to 1.5 times compared to HDPE geocell reinforced clayey bed. The effect of different patterns of placing coconut shell mat was also studied and discussed in the paper. The analytical studies have been conducted considering the reinforcement mechanisms of coconut shell mat embedded in the soil bed. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.