A nonlinear elastoplastic constitutive model is proposed
the elastic matrix can be calculated according to Duncen-Chang model and the plastic parts can be determined with the modified Cam-model. A new theory of modified layer-summation based on elastoplastic principle is presented; the theory has the advantage of layer-summation and can consider the character of nonlinearity and plasticity of soil
The effect of 3-D stress on deformation can be determined also. The new theory will provide a more perfect method to predict the settlement of foundation.