Bearing capacity of circular footings under surcharge using state-dependent finite element analysis

Footings are often used to support structures at sites where the soils near the surface are sufficiently strong to serve as a bearing layer. In this study, estimation of the bearing capacity of footings resting on a soil mass acted upon by a surcharge is investigated and related to the cone resistance qc. Non-linear finite element analyses based on a state-dependent stress-strain model were performed to obtain the load-settlement responses of axially loaded circular footings. Various values of relative density, lateral earth pressure ratio, depth of embedment and footing diameter were considered in the analyses. Based on the finite element results, load-settlement curves were obtained and used to determine the unit limit bearing capacity of the footings in terms of the cone resistance qc. Values of the unit bearing capacity for different values of surcharge were in a narrow range, while considerable variation in unit bearing capacity was observed with relative density DR. It was observed that the unit limit bearing capacity for a given surcharge, normalized with respect to qc, decreases as DR increases, with rates of change depending on the lateral earth pressure ratio K0. The effect of K0 was greater for lower DR values.