Abstract: The consolidation characteristics of rigid pile composite foundation is a key factor affecting the progress of the project. To study the consolidation properties of rigid pile composite foundation under external load, the equal strain assumption was modified based on stress-strain characteristics of rigid pile and its surrounding soil. Considering the smearing effect, the consolidation behavior of surrounding soil and underlying stratum, the governing equations for the average excess pore water pressure within the surrounding soil and the underlying soil were developed. According to the boundary conditions of a time-dependent loading and additional stress varied with time and depth, the analytic solutions of consolidation degree were derived based on the consolidation theory of double-layered ground. The proposed method was validated by numerical simulation method. The factors that affect consolidation properties were systematically analyzed. It shows that the analytical solutions have great agreement with the numerical simulation results. The average consolidation rate strongly depends on the penetration ratio of the rigid pile. The average consolidation rate is slower than that of natural ground when the ratio is small. The average consolidation rate of rigid pile composite foundation with a greater penetration ratio and a smaller pile end resistance coefficient is faster than that of natural ground. With the increase of pile penetration ratio, the ratio of the constrained modulus of the pile to that of the soil and the ratio of the constrained modulus of the cushion layer to that of the soil, the overall consolidation rate of the composite foundation is accelerated. With the increase of the replacement rate, the overall consolidation rate of the composite foundation decreases.

Key words: rigid pile composite foundation, modified equal strain assumption, consolidation characteristic, stress varied with depth, underlying stratum