Fragility assessment of highway embankment resting on liquefaction-susceptible soil

Abstract

Fragility curve defines the probability of a structure exceeding a damage level for various levels of loading intensity. The present study presents a vulnerability analysis of a road embankment structure exposed to liquefaction-induced deformation due to earthquake loading. The numerical simulations are based on 2D finite element analysis considering liquefaction-susceptible soil as an elasto-plastic effective stress-based UBC3D-PLM model. The model parameters are developed through a calibration procedure with respect to the laboratory test results from past literature. The level of damage is described in terms of peak embankment settlement (PES) with increasing ground motion intensity (PGA). The fragility analyses have been carried out using an incremental dynamic analysis (IDA) considering a set of 9 different ground motions, which have been scaled to 16 different intensity levels. A wide range of parameters, including the relative density of liquefiable foundation soil, the geometry of the embankment, the thickness of the liquefiable layer, and the effect of densification on embankment response, have been considered in order to evaluate the vulnerability response of embankment subjected to liquefiable foundation soil. Study envisaged the relative density and thickness of liquefiable layer as primary and embankment geometry as secondary parameters having significant effect.