Kinematic Soil-Pile Interaction under Earthquake-Induced Nonlinear Soil and Pile Behavior: An Equivalent-Linear Approach

The kinematic bending and filtering potential of a fixed-head pile are explored when large shear strains are generated in the surrounding soil during the passage of seismic waves. The problem is treated numerically by employing a freely available 1D code to derive soil response at free-field conditions and an advanced 3D finite-difference (FD) model of the soil-pile system. Three idealized soil profiles with varying stiffness and strength and a real layered site are considered under earthquake excitations of increasing intensity, allowing investigation of the pile's non-linear kinematic response under shear strains exceeding the threshold of an equivalent-linear approximation. Simple analytical solutions are revisited in the context of soil response close to failure, by means of the FD solution, and an equivalent linear approach is proposed for assessing kinematic pile-head bending and filtering action in the presence of large earthquake-induced shear strains in the soil and non-linear pile behavior. A practice-oriented procedure requiring only a pertinent 1D soil response analysis is proposed to address kinematic effects in seismic design of piles.