Abstract: A new composite pile consists of a Prestressed Highstrength Concrete (HPC) pipe pile inserts into a fresh soilcement mixed column before it is hardened. This new composite pile can be applied for the soil soft improvement projects. The paper presents the numerical analysis results by using ABAQUS software as well as the static loading test results. The numerical analysis studies the influence of various factors on the axial resistance of the composite pile. These factors include: the length of PHC pile; ratio of pile diameter to the tributary diameter of the composite pile; diameter of the soil cement mixed column and its stiffness; etc. The optimized PHC pile and the soil cement mixed column relationship are obtained. The analysis results indicate that the key factors that are impacting the axial resistance of the composite pile are the length of PHC pile and the ratio of pile diameter to the tributary diameter of the composite pile. The impact of the stiffness of the soil cement mixed column on the axial resistance of the composite pile is relatively small. The ratio of the PHC pile and to the soil cement mixed column should be between 3∶5 and 4∶5. The ratio of the PHC pile to the tributary diameter of the composite pile should be ranging from 0.19 to 0.25. The minimum diameter of the soil cement mixed column should be 300 mm greater than that of the PHC pile.

Key words: PHC Pile and soil Cement Mixed Column Composite Piles, The bearing performance, Influencing Factors, Numerical Analysis, Optimized Design