Model Tests and Fem Simulation of Some Factors Affecting the Bearing Capacity of a Footing on Sand

A series of model tests was carried out on a particular type of sand (Toyoura sand) with a target void ratio of 0.66 to study into the effects of the shape and depth of a footing and the load inclination on the bearing capacity of a rough and rigid footing on sand. The test results were numerically simulated by two-and three-dimensional FEM analysis using a constitutive model that has been developed for Toyoura sand based on the results from an extensive series of laboratory stress-strain tests. The effects of the following factors, among others, on the strength and deformation characteristics of sand are taken into account; a) pressure level; b) the intermediate principal stress; c) inherent anisotropy; d) non-linear strain-hardening and softening; e) non-associated dilatancy; and f) strain localisation into a shear band(s). The material model is coupled with an isotropically hardening, non-associated, elasto-plastic material description. The FEM simulation is consistent with the physical model test results. In some important aspects, the results from both the physical model tests and FEM simulation are not consistent with some of the previous proposals that have been widely used in practice: i.e., in the results of the present study, the bearing capacity of a rectangular footing is noticeably larger than that under purely plane strain conditions, and negative effects of load inclination and positive effects of footing depth on the bearing capacity are generally larger than those predicted by some previous proposals.