SOIL-PILE INTERACTION DURING LIQUEFACTION-INDUCED LATERAL SPREAD

Abstract

This paper describes a numerical model for the analysis of foundation piles subjected to large lateral ground deformation triggered by liquefaction. The model involves the use of p-y curves, but avoids the empiricism associated with the selection of degradation coefficients or reduction factors. To obtain a proper p-y characterization of the reaction between laterally deformed liquefied soil and an embedded pile, triaxial extension is recognized as the most appropriate analogue for the loading conditions. A suite of undrained triaxial extension tests was carried out using Nevada sand to establish the relevant strength and deformation parameters. Using the material parameters obtained from these tests, 2D FLAC analyses were performed to develop strain-softening p-y curves. Application of these p-y curves to the analyses of centrifuge experiments involving lateral spread effects on piles yields good agreement between the computed and measured responses. The strain-softening model provides excellent predictions of the measured peak and residual moments. Furthermore, the computed soil pressure diagrams agree well with the recommendations made by the Japan Road Association, which were calibrated using case histories from the 1995 Kobe earthquake. The same p-y curves were applied to the analysis of a field problem involving an actual pile foundation subjected to lateral spread effects during the 1964 Niigata earthquake.