Load transfer mechanism of composite pile composed of jet-mixing cement and PHC pile with core concrete

The composite pile composed of jet-mixing cement and PHC pipe pile with core concrete(CPCP) is a new kind of composite pile used in soft ground treatment. For practical project, the static load test associated with fiber Bragg grating(FBG) stress tests and numerical simulations was conducted to understand the load transfer mechanism of the composite pile. With the pile tests, the side friction resistance and the tip resistance were measured in terms of axial stresses under different loads. Then the compatible deformation of pipe pile and cement-soil is obtained associated with their stress distribution. The change rule of compression of each segment is also achieved with the imposed top load. Finally, the differences between general pipe pile and CPCP in terms of resistance characteristics were compared. It shows that: (1) load-displacement(Q-s) curve of pile head varies gradually;(2) pipe pile rather than cement-soil bears a majority of structural load, whilst the bearing capacity characteristics of the composite pile are similar to those of the rigidity piles;(3) pile tip resistance takes a rather smaller percentage of the top load, suggesting the same performance as that of friction piles. Distribution of pipe pile and cement-soil friction resistance is similar, about the ratio of CPCP diameter to PHC diameter.