Faculty Publications
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Item Shear Response of Pervious Concrete Column Improved Ground(Springer, 2021) Rashma, R.S.V.; Shivashankar, R.; Jayalekshmi, B.R.This study deals with numerical analysis of the shearing resistances of pervious concrete column improved ground vis-à-vis ordinary stone column improved ground. Analysis is done by numerically simulating a large shear test model, representing pervious concrete column improved ground. The parameters varied in this study are the depth of pervious concrete column/pile, floating and end-bearing piles, diameter, single pile and two-pile group and distance from the edge of loading area in the model. The shear response of improved ground is quantified by the applied strain controlled vertical load to the entire width of large shear test model that induces shear movements within the tank model. It is observed that the pervious concrete column improved ground shows better shear performance than ordinary stone column improved ground. It is also found that the pervious concrete column undergoes very small lateral deflections. It is also observed that more number of pervious concrete columns, and closer they are to the loaded area, better is the shear performance. © 2020, Indian Geotechnical Society.Item Liquefaction Mitigation Potential of Improved Ground Using Pervious Concrete Columns(Springer, 2022) Rashma, R.S.V.; Jayalekshmi, B.R.; Shivashankar, R.In this study, liquefaction mitigation potential of improved ground using pervious concrete column is being investigated. The seismic performance of pervious concrete column improved ground is compared with conventional stone column improved ground. Three-dimensional finite element analysis using OpenSeesPL software is conducted to study the ground lateral deformation and excess pore water pressure generation of pervious concrete column improved ground on a mildly sloping soil strata of infinite extent under seismic loading. The soil strata considered is fully saturated sand with an inclination of 4°. The parameters influencing seismic performance of improved ground like area ratio, founding depth of columns, diameter of columns and hydraulic conductivity of columns are considered. It is found from various response parameters that the pervious concrete column improved ground has better seismic performance than conventional stone column improved ground. The lateral deformation profile of pervious concrete column is found to be similar to that of concrete pile, allowing excess pore water pressure to dissipate through the pores of pervious concrete column. It is also concluded that pervious concrete columns could be used as an alternative to conventional stone columns to mitigate liquefaction to a larger extent. © 2021, Indian Geotechnical Society.Item Influence of Earthquake Characteristics on Pervious Concrete Column Improved Ground(Springer Science and Business Media Deutschland GmbH, 2022) Rashma, R.S.V.; Jayalekshmi, B.R.; Shivashankar, R.In this paper, the influence of earthquake characteristics on the seismic performance of ground improved with pervious concrete columns in place of conventional stone columns is presented. Two scaled earthquake ground motions with different seismic characteristics are applied to the finite element models of ground with and without column inclusions. Total stress analysis is also conducted and compared with effective stress analysis on maximum response profile along the depth of column improved ground. The study is further extended to sandwiched liquefiable soil deposits of varying thickness. It is noted that the average lateral displacement reduction of the pervious concrete column improved ground is 90% when compared to unimproved sand strata when subjected to two different earthquake excitations. It is found that the generation of excess pore pressure reaches near zero values when the permeability of pervious concrete column is greater than 0.3 m/s irrespective of the characteristics of the earthquake events. From total stress analysis and effective stress analysis, it is observed that for column improved ground, in addition to pore pressure build-up, the maximum response profile is highly influenced by significant duration and frequency of seismic excitation. The pervious concrete column performed better in homogeneous sand deposit as well as sandwiched liquefiable soil of varying thickness when subjected to different seismic excitations with different characteristics. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.Item Geofoam integrated separation layer for enhancing seismic resilience in modified piled raft foundations(Springer Science and Business Media B.V., 2024) Amalu, P.A.; Jayalekshmi, B.R.Modified Piled Raft (MPR) foundations have the potential to reduce seismic force transmission to the superstructure compared to connected piled raft foundations. However, the responses of the separation layer in improving the seismic resilience of the structure were not extensively parameterized before. To address this gap, the investigation explores the potential for enhancing the seismic resilience of MPR foundations in seismically active regions by integrating sustainable materials in the separation layer between the raft and pile group. A novel separation layer is proposed by integrating geofoams with different types of soils. The performance of this novel separation layer is explored through a comprehensive 3D finite element analysis under both static and dynamic loading conditions. Using the OpenSees software platform, an extensive numerical analysis was undertaken to examine the influence of various key parameters on the system's behaviour. A comprehensive analysis of these parameters was conducted to evaluate the responses of MPR foundations with and without geofoam in the separation layer, specifically in the context of ground motion analysis. Raft thickness, pile configuration, separation layer thickness, and the materials used in the separation layer were all considered. The findings indicate that raft thickness and pile length are crucial influencing factors on the dynamic response of the MPR system. Furthermore, the inclusion of EPS geofoam in the separation layer demonstrated its effectiveness in reducing the acceleration amplitude at the top of the raft by 44.25% and lateral displacement by 47.84%, effectively mitigating the impact of seismic waves reaching the upper surface of the raft. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Item Influence of Separation Layer Properties on Seismic Response of Modified Piled Raft Foundations(Springer, 2025) Amalu, P.A.; Jayalekshmi, B.R.Conventional piled raft foundations, with the raft and piles interconnected, severely restrict lateral movement, especially during seismic events. These constraints result in substantial stresses at the connection, posing a risk of potential breakage. Therefore, in seismic-prone areas, where transient lateral loadings of larger magnitudes are expected, conventional piled raft foundations are not feasible. Providing a separation layer between the raft and pile foundations is a viable solution to improve the performance of conventional piled raft foundations. The performance of such a modified piled raft system depends largely on the properties of the separation layer introduced. However, limited studies have been conducted to evaluate the seismic performance of these separation layers by considering the effect of soil–structure interactions. The present study thus aims to investigate the performance of modified piled raft systems by comparing them with their conventional counterpart. The existing conventional piled raft foundation of the Treptower building has been chosen as the prototype and is numerically analysed for static and dynamic loading conditions. Further, a separation layer has been introduced between the pile and raft, and the performance of the modified piled raft foundation is analysed under similar loadings. The results of these analyses are comprehensively compared to ascertain the performance of modified piled rafts under seismic excitation. It is found that the modified piled raft foundation with PE foam in the separation layer is advantageous in damping the propagation of seismic waves to the superstructure, reducing settlement and lateral displacements, and thereby decreasing the potential risk of failure of superstructures in seismic-prone areas. © The Author(s), under exclusive licence to Indian Geotechnical Society 2024.