Equivalent Linear Model for Predicting Settlements of Sand Bases

There are at least seven methods for estimating settlement of sand bases employing the Standard Penetration Resistance (SPT) N. A new method is presented. The new method is quasi-elastic. The modulus of deformation is calculated in terms of the SPT N values corrected for overburden. The modulus is dependent on effective vertical stress and vertical strain induced by foundation loads. A conventional analysis is then made using an equivalent linear model. The method was applied to reasonably documented case histories from three sites and the calculated settlements were in good agreement with recorded ones. The main features of the new method are that it accounts for increase in sand stiffness with increasing confining pressure due to in-situ stresses and foundation loads, and nonlinear load-settlement relationships of sand bases.