Lateral Inertial Pile–Soil Interaction Using an Analytical Model

The lateral inertial response of a single laterally loaded flexible pile embedded in soil with different depth-wise stiffness profiles is investigated using a recently developed two-parameter foundation model that explicitly incorporates shear interaction. This standalone model, calibrated against three-dimensional finite-element analysis, offers a simplified yet sufficiently accurate representation of pile–soil interaction. For soils with a constant stiffness profile, pile-head impedance functions are derived analytically, yielding closed-form expressions for stiffness and damping. For nonhomogeneous profiles, an energy-based approach is used to obtain curve-fit expressions. The model’s accuracy is comparable to rigorous numerical methods while maintaining the simplicity of subgrade reaction approaches. The influence of shear interaction on impedance functions is also examined. Neglecting shear interaction leads to an average underestimation of swaying and rocking stiffness by 6.75% and an overestimation of pile-head damping by 9.45% for free-head piles in soil with homogenous profile. For nonhomogenous profile, the pile-head stiffness is overestimated by an average of 9.3%, and the damping is underestimated by an average of 4.9%. Similar trends are also observed for fixed-head piles.