Seismic Analysis of Free Head Pile Under Combined Vertical and Lateral Load Embedded in Virgin and Improved Clayey Deposit

In the present study, force-based pseudo-static approach has been used to investigate the lateral behavior of pile under combined vertical and lateral load subjected to seismic motion. An attempt has also been made to consider top soil improvement to increase the lateral capacity of the pile under seismic condition. Soil nonlinearity for stiffness degradation has been taken into account by utilizing cyclic p-y curves. Finite element method has been adopted for the numerical solution, and element stiffness matrix has been proposed here in a concise form. A computer code in MATLAB environment has been developed to study the seismic response of pile embedded in homogeneous soft clayey deposit as well as improved soil. The study reveals that pile head stiffness reduces with increased normalized pile head deflection and increased vertical load on pile head, thereby reducing lateral capacity of pile. Ground improvement depth up to 4D-5D, significantly increases lateral capacity of pile. The present study also signifies that increasing vertical capacity of pile by means of increasing pile diameter or length might have an adverse effect on lateral pile capacity in seismic condition as with increased vertical load, lateral pile head stiffness reduces, and therefore, a certain depth of ground improvement around the pile might be done to keep lateral deflection within permissible limit.