Highway embankment fragility behaviour subjected to liquefaction-induced settlement

Abstract

The fragility curve, which specifies the likelihood that a structure would sustain damage that exceeds a certain threshold for different levels of loading intensity, is a newly developed method for the seismic risk assessment of all at-risk projects. Median and log-standard distribution are the two parameters constituting the cumulative lognormal distribution function, typically used to describe fragility curves. An investigation of the response of a road embankment geotechnical structure exposed to liquefaction-induced deformation driven by earthquakes is presented in the current work. The elasto-plastic and effective stress-based UBC3D-PLM model is used in the numerical analyses based on 2D FE analysis. A rigorous calibration process is carried out to generate the model parameters concerning laboratory test findings from past literature. With increasing intensity of ground motion (PGA), permanent embankment settlement (PES) is used to indicate the extent of the damage. A collection of 9 separate ground motions, scaled to different intensity levels, were used in the incremental dynamic analysis (IDA) that has been used to perform the fragility analyses. It has been observed that the embankment experiences more settlement even with low to moderate ground motion intensity due to the existence of the liquefiable foundation layer. To assess the vulnerability of an earthen embankment exposed to liquefiable foundation soil, different factors have been taken into account, including the relative density of the liquefiable underlying soil, the thickness of the liquefiable layer, and the geometry of the embankment (height and width). It has been noticed that liquefiable layer properties are the primary and embankment properties are the secondary parameters influencing the vulnerability of embankment supported on liquefiable soil deposit.