Simplified method for analysis of piles undergoing lateral spreading in liquefied soils

The analysis of piles subjected to lateral spreading is burdened by the uncertainties associated with the spreading of liquefied soils. Namely, it is very difficult to reliably predict the magnitude and spatial distribution of post-liquefaction ground displacements and also there are uncertainties regarding the stiffness and strength of liquefied soils undergoing lateral spreading. In view of the unknowns involved, there is a need for a sufficiently accurate, yet simple and rational method of analysis that will permit to efficiently evaluate the pile response for various magnitudes of ground displacements and stiffness properties of the spreading soils. In this paper a simple analytical solution is presented for evaluating the pile response to lateral spreading with due consideration of the kinematic mechanism associated with spreading of liquefied soils and the need to estimate the inelastic response and damage to piles. Particular attention is given to the loads arising from a non-liquefied crust layer at the ground surface and to the kinematic effects at the interface between the liquefied layer and underlying non-liquefied layer. A closed-form solution for linear behavior is first derived based on the classical equation for beam on elastic foundation. The method is then extended over the range of nonlinear behavior using the equivalent linear approach for simplified modeling of the deformational behavior of the pile and soil. Key parameters influencing the pile response and. being associated with intrinsic uncertainties are identified and discussed. The proposed method permits to estimate the inelastic response of piles, yet it is a simple analytical solution that requires a few conventional engineering parameters as input. The method is envisioned as a rational tool that will be of practical use in the preliminary assessment of piles and uncertainties involved.