STIFFENING EFFECT ON END BEARING GRANULAR PILES

The performance of ground improvement using granular piles (GP) is limited by its low strength and stiffness. If GPs are partially strengthened and stiffened near the ground surface, their overall performance gets enhanced several fold. Stiffening of GP can be achieved by replacing partially the upper portion of GPs with material having higher strength and deformation modulus, e.g. by geo-synthetic encased columns, SDCM (stiffened deep cement mixing), etc. Analyses of a single and group of two partially stiffened end bearing GPs is presented in terms of top settlement influence factor, settlement interaction factor for two-pile group, settlement reduction factor, percentage load transferred to the base, variation of normalized shear stress distribution along the length of the pile. Settlement influence factor decreases while the percentage load transferred to the base of increases with increase in the relative stiffness factor and the relative length of stiffening from top of the partially stiffened GP, both for single as well as for two pile group.