Conference Papers
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Item Experimental investigation on the stabilization of soft clay using granulated blast furnace slag(Institute of Physics Publishing helen.craven@iop.org, 2019) Preetham, H.K.; Nayak, S.; Surya, E.V.Soft clay is associated with a soft consistency and poor shear strength. High percentage fines lead to higher liquid limit and lower plasticity index. Low bearing capacity and excessive settlement lead to uneconomic engineering structure constructed over it. There is a serious need to mitigate this problem and hence soil stabilization is the need of the hour. In the present study, Granulated Blast Furnace Slag (GBFS) which is an industrial waste/by-product of steel industry is used as a stabilizer to improve the geotechnical property of the soft clay. Soft clay is replaced by granulated blast furnace slag in various percentages by weight (10%, 20%, 30%, 40% and 50%) and examined for its plasticity, compaction and strength properties of the mix. From the experimental investigation, it is shown that the plasticity index decreases and unconfined compressive strength (UCS) increases upon addition of slag to the soil. With the curing age, UCS value increased indicating the chemical reaction between free lime and soil. 40% slag replacing the soft clay is recommended as stabilizer as it gave the maximum increase in UCS value compared to the rest mix. Based on the laboratory work, it can be concluded that granulated blast furnace slag can be used as a potential stabilizer for soft clay and also largely solves the problem of disposal of slag. © 2019 IOP Publishing Ltd. All rights reserved.Item Numerical Modeling of Centrifuge Experiment on Vacuum Consolidation of Soft Clay(Springer Science and Business Media Deutschland GmbH, 2022) Sridhar, S.This paper presents the finite element (FE) modeling of centrifuge experiments on vacuum consolidation of soft clay deposits. FE analysis of centrifuge tests as a model scale was performed, and the comparison is made with the centrifuge tests modeled as a prototype. The effect of different material parameters namely unit weight of water and density, initial void ratio and permeability of clay at model and prototype were studied. FE analysis confirmed that the use of unit weight of pore water at 1-g as an input parameter results in an incorrect distribution of vertical effective stress. To correctly compute vertical effective stress, unit weight of water at N-g should be used. In order to model the centrifuge test exactly it would be appropriate to give the values of initial dry density, initial void ratio and the initial vertical stress corresponding to those at 1-g so that the final conditions after self-weight consolidation results in proper distribution of void ratio and other field variables. To correctly model the increase in seepage velocity with gravity in centrifuge tests, permeability must be increased by the same factor as the gravity. Four pore water pressure boundary conditions to model the vacuum pressure were analyzed through numerical runs. The numerical model at the model scale considering all factors analyzed earlier were used in modeling vacuum consolidation of soft clay. It was found that to accurately model the vacuum pressure, the vacuum pressure should be applied only at the top of the soil layer for accurate prediction of the field variables. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Finite Element Modelling of Foundation on Soft Clay Improved by Geocell and Boulder-Sand Layer: A Comparative Study(Springer Science and Business Media Deutschland GmbH, 2025) Rao, M.S.; Sridhar, G.Rapid infrastructure development urges for sufficient competent ground, which is currently scarce. Thus, the major focus of geotechnical engineers is the development of techniques for improving poor soil. A variety of strategies are used to reduce post-construction settlement, increase the shear strength of the soil, enhance the bearing capacity of the soil system, and improve the stability of superstructures. Among these, soil replacement is the simplest and most widely used method, while geocell reinforcement has been found to be an effective methodology. The three-dimensional structure of geocell provides better lateral confinement to the infill soil, improving its ability to support loads. However, because of its intricate honeycomb structure, numerical modelling of geocell has always proven difficult. Thus, an attempt has been made to generate a three-dimensional model of geocell using PLAXIS 3D. Finite element model was validated using laboratory model test results. A numerical analysis of footing resting over unimproved soft soil and soft soil improved by boulder-sand replacement and geocell reinforcement has been carried out. It was found that by replacement and reinforcement techniques, the performance of the footing can be doubled. The influence of width and depth of the boulder-sand layer and depth of the first geocell layer on bearing capacity improvement has been studied. The effect of the depth of boulder-sand bed on the influence factor was found to be higher compared to the effect of width. Maximum improvement by the inclusion of geocell was observed when it was placed in the middle of the sand layer with an improvement factor of 2.25. Further, using soil investigation data from in situ and laboratory tests, the concept has been extended to a field problem. © Deep Foundations Institute 2025.Item Critical Review and Finite Element Analysis of Smear Zone in Soft Clay Improved by Prefabricated Vertical Drains(Springer Science and Business Media Deutschland GmbH, 2025) Mahesh, D.; Sridhar, G.Structures built on soft soils are often affected by settlement problems. Over the past decades, one of the best methods to accelerate the consolidation process is preloading technique with pre-fabricated vertical drains. However, while installing these drains the soil around the drain gets disturbed, which in turn reduces the permeability of soil in radial direction. This disturbance is known to be smear effect and the region of this disturbed soil is the smear zone. This paper presents a state-art-of-the review on analytical, laboratory, field and numerical studies on the smear zone behaviour. Pore pressure variation, water content and permeability in the smear and undisturbed zone are compared. Finite element modeling carried out for better understanding of consolidation behaviour of soft clay improved with PVD is also presented in this paper. The effect of smear is considered in the finite element model and the results from the finite element model are compared with laboratory test results. The soil behaviour is modelled using the modified cam-clay model and the ABAQUS finite element application is used for numerical modelling. Based on the results, the time-settlement data and pore pressure dissipation predicted by the numerical model were comparable with the laboratory results reported in the literature with a variation of upto 10%. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.