A simplified nonlinear settlement prediction model for foundations on sand

Abstract

This paper presents a simple method for predicting the settlement of spread foundations on sand operating under typical working loads. The method accounts for the well known effects on soil stiffness of strain, stress level, and density dependence, but adopts the simplifying assumption that the stress distribution beneath a loaded foundation can be obtained from Boussinesq's equations for an elastic half space. Despite this simplification, the method is shown to predict foundation responses that closely match those computed using more sophisticated finite element (FE) analyses and those measured in laboratory footing tests, where the stiffness characteristics in triaxial compression were well defined. The method is also seen to predict general variations of foundation settlement with bearing pressure, foundation width, and degree of preloading that are entirely consistent with empirically observed trends. It is concluded that satisfactory settlement predictions for shallow foundations on cohesionless soil may be obtained using Boussinesq's equations if the soil's vertical stiffness characteristics, as inferred from triaxial compression data, can be specified with some degree of precision.Key words: stiffness, settlement, cohesionless soil.