Analytical studies on the behaviour of underreamed piles under lateral load

Foundations of certain types of structures are subjected to high magnitudes of lateral forces in addition to compressive and uplift forces. The underreamd pile provides a solution in the above situation as these have considerable uplift resistance and can resist the lateral loads more effectively. In the present study, the ANSYS software has been used to study the behaviour of underreamed piles under lateral load in both clay and sand. 3-D half symmetric analysis was carried out by using 10-noded tetrahedron elements for both pile and soil. The interface is modelled using 8-noded quadrilateral elements with the coefficient of friction as the characterising property. On the material side, while the pile is linear, the soil and the pile-soil interface are taken as nonlinear. The nonlinear analysis is 'incremental-iterative-mixed' leading to high accuracy. Post processing of results includes deformation vectors, stress contours and contact pressures and frictional stresses at the interface. Three types of clays, viz., 'soft', 'medium' and 'stiff, and sands, viz., 'loose', 'medium' and 'dense', were used in the analyses for different stem and underrearn diameters and the results are presented along with the ultimate values of loads.