End bearing encased stone columns and finite element modeling of floating encased stone columns in soft clay


Laboratory model tests were performed on end bearing stone columns confined with bamboo made partial and full length encasements in very soft Marin clay. Effectiveness of the natural bamboo encasement was checked in comparison to a full length polyester geogrid encasement. Experimental results indicated improved footing capacity over column treated clay bed with increase in the length of bamboo encasement. Maximum footing capacity was achieved with full length bamboo encasement. The proposed bamboo encasement was found effective to produce significant improvement in footing capacity. An analytical study was performed with some simplified assumptions. It was observed from the analytical study that with increasing applied pressure, lesser hoop strain developed in the full length bamboo encasement as compared to the full length polyester geogrid encasement. To simulate the real life applications of stone column technique especially in extremely soft soil in coastal areas, large scale numerical studies were performed on floating encased stone columns in very soft clay using the finite element program ‘Plaxis 3D’. The effect of length and stiffness of the encasement on the floating column behavior was studied.