Dynamic Interactions of Inclined Piles and Pile Groups in Nonhomogeneous Anisotropic Soils

This study aims to advance the understanding of the dynamic response of inclined pile groups embedded in nonhomogeneous anisotropic soils through a hybrid analytical–numerical approach. The dynamic pile–soil–pile interaction under both vertical and lateral loading conditions is modeled using radiation elements defined along the piles, fully satisfying the radiation conditions at infinity. The dynamic response of the radiation elements buried in exponentially graded transversely isotropic soils subjected to vertical and lateral vibration modes is analytically derived in the frequency domain using a set of complete potential functions for nonhomogeneous anisotropic materials. Numerical results, along with comparisons to existing analytical and numerical solutions, are provided, highlighting the validity and capabilities of the hybrid method. The lateral and vertical dynamic impedance functions of inclined piles and pile groups are obtained, and the influence of soil nonhomogeneity, pile inclination angle, soil anisotropy, pile group configuration, partial embedment of piles, and excitation frequency on the dynamic pile–soil–pile interaction is particularly emphasized. The results demonstrate a strong sensitivity of response to both degrees of nonhomogeneity and anisotropy, with the extent of the sensitivity influenced by the loading conditions and the pile inclination angle. The benefit of inclined piles in enhancing lateral stiffness depends on the pile arrangement, with maximum horizontal impedance values achieved when the piles are excited in the direction of their inclination. A nonhomogeneity-dependent cutoff frequency is identified in the impedance functions, below which elastic waves from the vibration of inclined piles cannot propagate through nonhomogeneous soils.