Centrifuge study of bending response of pile foundation to a lateral spread including restraining effect of superstructure

Centrifuge modeling was used as main tool to study the restraining effect of the superstructure above ground on the response of a single pile to lateral spreading. Two- and three-layer soil profiles were used with free and fixed head conditions for the pile. The superstructural horizontal stiffness was modeled by a horizontal spring attached to the top of the pile having stiffhess, k, with the value of k varying between tests from very flexible to very stiff. Pile bending moments and displacements were monitored, as well as displacement of the restraint and accelerations, displacements and excess pore pressures in the soil. Consistent results were obtained in the experiments, which provided considerably insight on the factors controlling pile response to lateral spreading in the presence of significant superstructural lateral or rotational stiffness. Analyses and interpretations of the centrifuge experiments using both Limit Equilibrium and Beam-on-Winkler Springs approaches showed reasonable good agreement, with some overprediction of moments for cases of large k. These analyses also showed changes in the direction of the lateral pressures applied by the top nonliquefiable layer to the pile, depending on the value of k, and they indicated the need to introduce kinematic soil-pile considerations to determine the signs of these pressures prior to any limit equilibrium analysis.