Bearing Capacity of Shallow Foundations on Sand: A Relative Density Approach

An accurate prediction of bearing capacity of shallow foundations on granular soils has been historically complicated by effects due to scale of the foundation. These effects are due to the nonlinear strength behavior of the granular soil and the phenomenon of progressive failure. The former can be conveniently accounted for by strength-dilatancy relationships. It is proposed that the effect of progressive failure on ultimate bearing capacity can be described in terms of the relative dilatancy index inherent in strength-dilatancy relationships. A design approach to bearing capacity based on these considerations is presented. The approach is calibrated using bearing capacity results from studies spanning the past 20 years. The solution is shown to work well for the sands examined and is useful in that the proposed process by which strength parameters are determined reduces, or may eliminate, the need for laboratory or in situ shear testing, while increasing the accuracy of the predictions made when compared to conventional methods.