Seismic response of an end-bearing pile in a transversely isotropic elastic medium under vertical S-waves

Anisotropy is an inherent characteristic of subgrade soils, causing significant variations in the dynamic behavior of the pile embedded in them under different loading conditions. This research develops a novel model to examine, for the first time, the dynamic behavior of an end-bearing pile embedded in an anisotropic elastic medium subjected to vertical S-waves. The pile is modeled as a Euler-Bernoulli beam, while the surrounding soil is treated as a transversely isotropic (TI) elastic material. The one-dimensional free-field and three-dimensional scattered-field motions in the TI elastic medium under S-waves are obtained within the frame of dynamic continuum model. The developed model is checked for accuracy against established analytical solution. Key parameters, such as the anisotropic modulus ratio of the TI soil, pile radius, are systematically studied to assess their effects on the kinematic behavior of the system. Results reveal that the soil anisotropy would significantly alter the kinematic behavior of the pile and surrounding soil system, notably impacting the amplification factors for pile displacement and rotation and the horizontal movement of the soil. These findings highlight the necessity of considering soil anisotropy in the seismic design and analysis of pile foundations to ensure structural safety and performance under earthquake.