Abstract: Considering the annular drainage section of concrete-cored sand-gravel pile composite foundation, both radial and vertical flows within the sand-gravel pile and soil construction disturbance, using the initial condition of load beared by soil and pile, the governing equations of consolidation problem of composite foundation with concrete-cored sand-gravel piles are derived; the analytical solution to the governing equations is obtained; the overall average degree of consolidation defined in terms of stress and deformation is given; and the influences of several factors, such as the permeability coefficient of sand-gravel piles, diameter ratio of concrete-cored pile and sand-gravel pile on the consolidation of composite foundation are analyzed. The results show that the solution of overall average degree of consolidation in terms of stress is not equal to that in terms of deformation; the greater the permeability coefficient of sand-gravel piles is, the faster the consolidation rate is; under the condition of a certain diameter size of sand-gravel piles, with diameter of concrete-cored pile increasing, the consolidation rate is increased at first and then decreased. Finally, a comparison between the present solution and two previous solutions is made. Compared with two previous solutions，the present solution considers the influences of annular drainage section and load beared by soil and pile together, the overall average degree of consolidation calculated by the present solution is between two previous solutions.

Key words: composite foundation with concrete-cored sand-gravel piles, radial flow, consolidation, annular drainage section