Based on the principle of semi-analytical method and the assumption of transversely isotropic material of composite foundation

a semi-analytical element method has been presented to calculate the settlement of composite foundation. Vertical displacement is discretized as polynomial expressions

and horizontal displacements are modeled by means of displacement functions in two directions to simulate infinite field. For one direction discrete and two directions analytical

this method can simplify 3-dimensional computation of displacements into one dimension

it can save computation time dramatically for its quick convergence. Furthermore it can simulate infinite soil field and acquire precise results for avoiding introduce redundant boundary condition compared with FEM

An example has been calculated with semi-analytical element method by changing substitution ratio

improved depth and modulus ratio of pile to soil of composite foundation. The results indicate that the substitution ratio and the modulus ratio of pile to soil have little effect on reducing displacement; while increasing improved depth can affect settlement obviously. So it is reasonable to increase improved depth to reduce composite foundation settlement under the circumstance that the optimum design is controlled by ground settlement.