General non-axisymmetric 3D model for vertical vibration of large-diameter concrete-cored cement-soil mixing piles in low-strain tests

Concrete-cored cement-soil mixing (CCM) piles are widely used to improve the bearing capacity of soft coastal soils. Obviously, in the low-strain test, when the core-pile is a pipe pile and the excitation load is eccentric, the large-diameter CCM pile-soil system exhibits radial heterogeneity and non-axisymmetry. Thus, the existing traditional “pile-in-pile” model is not suitable anymore. In this paper, a general non-axisymmetric 3D model is established to simulate the vertical dynamic characteristics of large-diameter CCM piles during the low-strain test. In this model, both the “radial invariability assumption” and “pile-in-pile” model are introduced, which makes this model suitable for the large-diameter CCM pile with equal-pipe-core and equal-solid-core under eccentric load. First, the general non-axisymmetric 3D model presented in this paper is simplified for comparison with other existing axisymmetric and non-axisymmetric 3D pile models to verify its rationality, respectively. Then comparing with the finite element model (FEM) to verify the rationality of the general non-axisymmetric 3D model for large-diameter CCM piles with equal-pipe-core and equal-solid-core. Finally, the interface reflection interference mechanism and the vertical vibration characteristics of large-diameter CCM piles are investigated.