S. R. Gandhi

Bio: S. R. Gandhi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Pile & Expansive clay. The author has an hindex of 11, co-authored 21 publications receiving 612 citations. Previous affiliations of S. R. Gandhi include Sardar Vallabhbhai National Institute of Technology, Surat.

Behavior of Stone Columns Based on Experimental and FEM Analysis

Abstract: A detailed experimental study on behavior of single column and group of seven columns is carried out by varying parameters like spacing between the columns, shear strength of soft clay, and loading condition Laboratory tests are carried out on a column of 100 mm diameter surrounded by soft clay of different consistency The tests are carried out either with an entire equivalent area loaded to estimate the stiffness of improved ground or only a column loaded to estimate the limiting axial capacity During the group experi- ments, the actual stress on column and clay were measured by fixing pressure cells in the loading plate Finite-element analyses have also been performed using 15-noded triangular elements with the software package PLAXIS A drained analysis was carried out using Mohr-Coulomb's criterion for soft clay, stones, and sand The numerical results from the FEM are compared with the experimental results which showed good agreement between the results Columns arranged with spacings more than 3 times the diameter of the column does not give any significant improvement Based on the results, design charts are developed and a design procedure is suggested

Densification of Pond Ash by Blasting

Abstract: Fly ash from thermal power plants is disposed, in huge quantities in ash ponds, which occupy large land areas otherwise useful for agriculture, housing, or other development. For effective rehabilitation of ash ponds, densification of the slurry deposit is essential to increase the bearing capacity and to improve its resistance to liquefication. Extensive field trials were carried out to evaluate the effectiveness of deep blasting for densification of deposited fly ash. Ninety explosions comprising 15 single blasts, with varying depths and quantities of charges, and 3 group blasts, each having 25 charges placed at various spacings, were carried out. The compaction achieved in terms of an increase in relative density was evaluated from surface settlement measurements. Extensive field monitoring was undertaken through pore-water pressure measurements, vibration measurements, penetration tests, and block vibration tests. For the average charge of 2–4 g of explosive per cubic meter of untreated deposit, the average relative density was found to improve from 50% to 56–58%. Analysis of the test results indicates that deep blasting may be an effective technique for modest compaction of loose fly ash deposits. The field testing program presented in this paper provides valuable information that can be used for planning blast densification of fly ash deposits.

Group effect on driven piles under lateral load

Abstract: The behavior of a pile group under lateral load is studied through laboratory experiments on aluminum pipe piles with outer diameters of 18.2 mm. Piles were driven in medium to fine sand with 60% relative density in different configurations and were subjected to lateral load under fixed head conditions. Some of the piles were instrumented with strain gauges to measure bending moments at varying depths. To quantify the effect of pile driving, the behavior of a single driven pile is compared with that of a bored pile. Test data are analyzed to arrive at the group effect for various spacings. The results are presented in a nondimensional form and a method for the prediction of field group behavior is illustrated. The predictions are compared with the field results from the literature and are found to be in favorable agreement.

Behaviour of Lime Treated Cured Expansive Soil Composites

Abstract: Expansive soils have the tendency to undergo volume change behavior and cause large uplift pressures and upheaval of structures built on them. Avoiding expansive soil in most of the cases is not practically possible, hence stabilization practices are undertaken to treat them. Chemical stabilization through lime is the most sought after treating method. In this study, soil from an expansive soil site, Siruseri near Chennai, was treated with lime to understand the microstructural changes taking place and its influence on the macro structural properties. X-ray diffraction, SEM and microporosimetry were the techniques used to understand the microstructural properties of lime treated soils. The expansive soil was treated with different percentage of lime, 2, 4, 6, and 8 % and cured for 3, 7, 14, and 28 days. The concept of lime modification optimum (LMO) was used as a reference to understand the progression of lime reactions. The change in the physical properties of the soil was determined through UCC, chemical batch testing, pH and chemical conductivity. The lime addition higher than the LMO brings about more permanent pozzolanic reactions which cause tremendous increase in strength. The time dependency of the reactions was observed through the change in pH values, conductivity and batch test results. At the microstructural level, lime addition reduces the specific surface area and increases the pore size. The SEM results also revealed larger clusters and aggregation of the clay particles.

Pile Foundation Analysis And Design

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Stabilization of a Clayey Soil with Fly Ash and Lime: A Micro Level Investigation

Abstract: Pavement structures on poor soil sub grades show early distresses causing the premature failure of the pavement. Clayey soils usually have the potential to demonstrate undesirable engineering behavior, such as low bearing capacity, high shrinkage and swell characteristics and high moisture susceptibility. Stabilization of these soils is a usual practice for improving the strength. This study reports the improvement in the strength of a locally available cohesive soil by addition of both fly ash and lime. Analysis using X-ray diffraction, scanning electron microscopy, coupled with energy dispersive spectroscopy, thermal gravimetric analysis, zeta potential and pH value test was carried out in order to elucidate the stabilization mechanism. The micro level analysis confirmed the breaking of montmorrillonite structure present in the untreated clay after stabilization. In the analysis, it was also confirmed that in the stabilization process, pozzolanic reaction dominated over the cation exchange capacity.