Pile Stress Estimation Based on Seismic Deformation Method with Embedment Effects on Pile Caps

Abstract

A pseudostatic analysis, based on the beam on nonlinear Winkler-spring method considering the seismic earth pressure and side friction acting on embedded pile caps, was developed to estimate pile bending moments and shear forces. To verify the proposed method’s effectiveness, the authors conducted six dynamic centrifuge tests on a superstructure-footing model supported by 2×2 piles in sand deposits comprising a dry sand layer over liquefied soil. The seismic earth pressure, vertical wall friction at the active and passive sides, and friction at the sidewalls of the pile caps were separately measured by two-dimensional load cells during shaking. The seismic total earth thrust and side friction estimated by the proposed method showed good agreement with the experimental results for both the amplitude and phase difference to the superstructure and the pile cap inertia forces. The estimated bending moment and shear force in the piles also showed reasonable agreement with the experimental results; they were able to account for differences in the pile rigidity and soil relative density.