Effective Stress Analysis of Pile Foundations in Liquefiable Soil
An advanced dynamic analysis based on the effective stress principle is used to evaluate the seismic performance of foundation piles of a bridge pier in Christchurch. The employed method permits accurate simulation of the ground response in liquefying soils including the process of excess pore pressure build-up and associated highly-nonlinear stress-strain behaviour of soils. In the analysis, complete liquefaction developed from 11 m to 17 m depth resulting in lateral ground displacements of about 28 cm and consequent damage to the pile at the pile head where the peak bending moment exceeded the yield level. Characteristics of the ground response and behaviour of piles are discussed using computed time histories and maximum values of accelerations, displacements, excess pore water pressures and pile bending moments. Results of the effective stress analysis are further examined through comparisons with a conventional analysis based on the pseudo-static approach.