Abstract：Based on Geddes stress solution and considering 3 dimensional stress of soil，a new theory on settlement calculation of single pile is presented according to Duncan-Chang constitutive model and modified layer summation. Compared with general method based on Geddes stress solution，three improvements are made，that is，(1) adopting Geddes 3D stress solution，its effect on settlement of single pile can been calculated，(2) Duncan-Chang model is used to study the settlement of pile and the nonlinear character is tics of soil can been considered，and (3) using modified layer summation，the layer character is tics and lateral deformation of soil can been computed. Therefore，the proposed method is more perfect in theory，and calculation amount is moderate to practical application.
