Determination of Depth Factors for the Bearing Capacity of Shallow Foundations in Sand

Abstract

The bearing capacity of shallow foundations is a traditional problem in geotechnical engineering. Many authors have contributed to the solution of this problem using an equation valid under ideal conditions, such as strip foundation under vertical and centred loading and assuming the superposition of the separate effects of self-weight and surcharge. Successive corrections are made to this equation using factors which take into account conditions different from the ideal ones. Among these corrections are the depth factors, which consider the resistance of the soil above the foundation level. In this work, the shallow foundation is considered in sand, and its strength is modelled by an associated Mohr-Coulomb criterion. Approximations to the depth factors are determined using a finite element formulation based on a strict implementation of the upper bound limit analysis theorem, which allows to obtain an optimal failure mechanism and to determine the limit loads. A comparison with previously published solutions is presented, and values for the depth factors are proposed. Following proposals by other authors, depth factors which take into account the superposition of effects of the bearing capacity equation are presented.