Field and 3D numerical investigation on bearing characteristics of the long-core SDCM piles under vertical load in sandy soil

The stiffened deep cement mixing (SDCM) pile is a new composite pile type, which is a stiffened core inserted into the cemented soil, compared to the DCM pile structure. The SDCM pile not only combines the advantages of DCM piles, but also improves the corresponding bearing capacity. In this paper, the bearing characteristics (the ultimate bearing capacity, the pile end resistance and the pile side friction) of PHC pipe pile and the long-core SDCM piles with number of different piles are investigated through field tests. The ultimate bearing capacities of PHC pipe pile, the long-core SDCM pile and the double long-core SDCM pile are 5.82, 8.23 and 14.67 MN. Combined with finite element analysis, it was found that the long-core SDCM pile is a friction pile in sandy soil, the cemented soil can provide lateral friction resistance and its role in bearing the vertical load is cannot be ignored. Parametric analyses were carried out for parameters: the length ratio of the cemented soil and PHC pipe pile (LC/LP), the radius ratio of the cemented soil and PHC pipe pile (RC/RP) and the modulus of elasticity of PHC pipe pile (EP) on the long-core SDCM pile with the objective of ultimate bearing capacity. The ultimate bearing capacity will be increased with increasing in LC/LP and RC/RP, and changes in EP will not affect the ultimate bearing capacity. Finally, the bearing capacity equations of the long-core SDCM pile were adjusted with the results of the study.