Abstract: A low-grade concrete-cored sand-gravel pile composite foundation was a new soft ground improvement method. A consolidation calculation model considering impeded boundary conditions was presented. While considering the hole pressure continuous problem of an overlying soil layer and a reinforce field, according to consolidation theory of double-layered soft clay composite ground, the consolidation problem of a low-grade concrete-cored sand-gravel pile composite foundation is translated into a consolidation problem of an equivalent double-layered foundation, and corresponding analytical solutions are solved.The comparison between the calculated results and the filed measured data showed that the calculated excess pore water pressure, the consolidation degree and the settlement-time relationship were consistent with those of filed data respectively.