NONLINEAR LATERAL RESPONSE OF PILE GROUP IN CLAY USING THE MODIFIED CAM CLAY SOIL MODEL

Abstract

Lateral pile response of the 3 × 3 square pile group has been investigated in terms of lateral displacement and maximum bending moment using three-dimensional finite element analysis. Soil is represented using 8-node isoparametric elements. Piles and pile cap are modelled using 20-node isoparametric elements. The 16-node isoparametric interface elements are used to establish the continuity between the pile and surrounding soil. Soil is represented by the modified Cam clay criterion. The entire code has been developed in FORTRAN 90. The parametric study has been performed to investigate the effect of yield criteria, soil modulus, pile spacing, pile diameter and pile length-to-diameter ratio on the response of the 3 × 3 pile group embedded in clay. A considerable effect of these parameters is observed. It is found that the maximum bending moment in the middle row of the pile group is higher than the front and rear rows for all cases considered in the study. The pile displacement and bending moments in the pile group reduce with an increase in soil modulus, pile spacing and pile diameter. As pile slenderness is increased, it causes an increase in displacement of the pile and a decrease in the maximum bending moment. The modified Cam clay model predicts greater displacements as compared to the Mohr-Coulomb model highlighting the impact of p0 on the yield surface. From the results obtained, the ultimate loads are predicted at a displacement of 5 mm, 10 % of diameter and 20% of diameter.