Load carrying capacity of stone columns embedded in compacted pond ash

Abstract

Pond ash deposits possess high compressibility, low bearing capacity so acres of land get wasted. Improvement of load carrying capacity of ash ponds will make them suitable for residential or commercial use. Stone or compacted stone columns is a technique of soil reinforcement that is frequently implemented in soft cohesive soils to increase the bearing capacity of the foundation soil, to reduce the settlement, and to accelerate the consolidation of surrounding saturated soft soil. The stress-strain behavior of the granular column is governed mainly by the lateral confining pressure mobilized in the native soft soil to restrain bulging collapse of the granular column. The purpose of this work is to assess the suitability of reinforcing technique by stone columns to improve the load carrying capacity of pond ash deposits through several laboratory model tests. This objective is achieved in two parts. In the first stage the characterization of pond ash is made along with the evaluation of the mechanical properties like compaction characteristics under different loading conditions, evaluation of shear strength parameters using Direct shear test, Unconfined compression test, Triaxial test at different testing conditions. This is done basically to find out the inherent strength of the pond ash compacted to different densities and at different degree of saturation. In the second series of tests the shear parameters of the compacted pond ash samples reinforced with stone columns of varying area ratios and length ratios are evaluated from triaxial compression test. In addition to this stone columns having different area ratios and length ratios are introduced in compacted pond ash beds and the bearing capacity of the composite system is evaluated through a series of footing loading tests. For this a circular footing of 75mm in diameter is used.