Abstract: A set of approximate analysis formulas of pile-soil system in rigid pile composite foundations is derived. The element-free method is used to simulate the raft on the composite foundations, and the finite element method to solve the cushion. A computation method of raft foundation on variable stiffness rigid pile composite foundations is established by coupled the pile-soil system and the cushion as well as the raft, based on the displacement continuity. The reasonability and reliability of the proposed method are showed by the results of a large-scale model experiment.

Key words: variable stiffness, rigid pile composite foundations, pile-soil system, element-free method, finite element method, raft foundation