The horizontal displacement of the composite ground improved by rigid piles is negligibly small

thus the only remaining component is vertical settlement. Equilibrium equations

geometry equations and physical equations are used to derive the governing equation of the problem. Boundary condition at the soil-pile interface is accounted at two different states: the displacements of the pile and the surrounding soil are compatible or slippage is developed at the interface. The displacements of the pile and soil can be solved by finite difference method from the governing equation. Then skin friction on the pile can be predicted. By comparing with finite element analysis and the measured data in site

the simplified method is verified and is convenient to be used in engineering design.