Settlement of Shallow Foundations on Sand

A new method for estimating the settlement of shallow foundations on sand is presented. The method is based on elastic stress-strain theory and is designed for use with soil data from the Standard Penetration Test (SPT). The elastic modulus is assumed to vary with mean effective normal stress and strain level. The variations of modulus with depth and the effects of footing size and shape, depth of embedment and groundwater level are introduced through their effects on the mean effective normal stress. The non-linear nature of the stress-strain relation is based on a normalized version of the Seed-Idriss curves, which relate shear modulus to strain level and relative density. SPT data are used to estimate relative density. In the general solution, the zone of influence beneath the footing is divided into sublayers and the foundation load is applied in increments. Then the incremental load solution is used to develop a simplified procedure in which the total load may be applied in one increment. The proposed method is applied to data from published case histories. The results of the proposed method are shown to compare favorably with those from other currently used methods.