Vertical Dynamic Response of a Pile Embedded in Layered Transversely Isotropic Unsaturated Soils

This paper investigates the dynamic response of a pile embedded in layered transversely isotropic unsaturated soils subjected to a vertical external excitation. The quintessential Biot biphasic model for saturated media is replaced with a triphasic model for unsaturated media, which simulates more realistic terrestrial subsurface soil characteristics. With the aid of the boundary element method (BEM), the soil around the pile is divided into a series of elements and the Green's function is obtained by the extended precise integration method (EPIM), while the pile is modeled as a 1D bar based on the finite element method (FEM). Thereafter, the soil-pile interaction formulation is acquired and further solved by the coupling of the BEM-FEM. The correctness of the proposed theory is verified by a comparison example with the existing results. A series of parametric studies are further provided to discuss the influences of degree of saturation, pore size distribution, and air-entry pressure on the dynamic behavior of the pile.