Numerical study of contact stresses under foundations resting on cohesionless soil: Effects of foundation rigidity and applied stress level

Abstract

The effects of foundation rigidity and applied stress on the distributions of contact stresses beneath circular foundations resting on sandy soil were investigated in this paper. Three foundation cases were considered in this study; one case considered rigid foundations behavior with Kr value of 1 (Kr is the relative soil/foundation stiffness index) and two cases considered non-rigid foundations behavior with Kr values of 0.05 and 0.005. The built-in material models of the Finite Element (FE) program ABAQUS were used to capture the stresses at the contact surfaces between the soil and the foundation at different applied loading levels (from 5%-100% of the ultimate bearing capacity of the foundation) for the three foundation cases. The FE analysis results indicated that the contact stresses (qc) are strongly dependent on the relative soil/foundation stiffness index (Kr) and the ratio (q*) of the applied stress on the foundation (q) relative to the ultimate bearing capacity of the foundation (qu). For a rigid foundation, the contact stress distribution was found to have either a parabolic shape at the ultimate (q* = 1) with peak contact stress of 1.4q or a saddle shape for q* < 1 with peak contact stress that ranges from 1.3–1.5 q. For a non-rigid foundation, contact stresses distribution has a saddle shape at all q* values with a non-zero stresses at the edges and peak stress that ranges from 1.1–1.38 q. The numerical simulations results were then interpreted and presented in form of dimensionless charts, which in turn, will enable the estimation of the contact stress at any point within the contact area between the foundation and the soil.