Behavior of Granular Pile and Granular Piled Raft

Granular pile, also popularly known as stone column, is an economical and efficient ground improvement technique to treat variety of soils. Depending on loading, geometry and spacing pattern, granular pile may fail individually or as a group. Bulging failure of granular pile is the most common failure criterion among the possible failure mechanisms – punching failure, shear failure and bulging failure. In this study, Finite Element analyses have been performed using commercially available software PLAXIS 2D to understand the bulging and the load-settlement behavior of both single floating granular pile and granular piled raft embedded in a soft clay deposit. Elastic-perfectly plastic response (Mohr-Coulomb criterion) is used to model both the granular pile and the soft clay. Parametric study is carried out by varying the properties of clay and granular pile to understand and quantify (a) the bulging along the depth of the pile with and without raft, and (b) the load-carrying capacity of granular pile and piled raft. Critical length of granular pile is also proposed for the cases considered in the study