PFC/FLAC 3D coupled numerical modeling of shallow foundations seated on reinforced granular fill overlying clay with square void

Abstract

This paper investigates the response of a circular shallow foundation constructed above a reinforced granular fill over clay deposit containing continuous square void. The numerical computations have been carried out employing a Finite Difference-Discrete Element (FDM-DEM) hybrid method. In the numerical simulations, the influences of the geometry and position of a square void with different dimensions and positions on the ultimate bearing capacity of the overlying shallow foundation, its load–displacement response, geogrid response and also the contact force network (CFN) underneath the footing have been rigorously examined. Moreover, the effects of the undrained shear strength of the underlying natural clayey deposit and the intervening geogrid stiffness on the behavior of surface footing have been evaluated. Results indicate that the bearing capacity of footing decreases by an increase in the width of the void while increasing the horizontal and vertical distances of void from the centerline of the surface footing suppresses its adverse effect. The negative impact of void on the bearing capacity of surface footing declines as the undrained shear strength of underlying clayey deposit increases. On the other hand, using a geogrid layer with higher stiffness leads to an increase in the ultimate bearing capacity of the overlying footing.