Evolutionary Intensity Measures for More Accurate and Informative Evaluation of Liquefaction Triggering

Abstract

Soil liquefaction is a seismic hazard that can have a devastating effect on the stability of buildings, bridges, dams, and other critical infrastructure elements. Accurate evaluation of liquefaction hazards requires accurate evaluation of the potential for triggering of liquefaction, and its effects. A recently developed framework for evaluation of liquefaction hazards considers the timing of the liquefaction process, and requires consideration of the response of liquefiable soils to transient loading histories – an aspect of behavior of liquefiable soils that has not previously been quantified. The development of this framework served as the motivation for the current study. Specifically, the goal of this study was to evaluate evolutionary intensity measures, or measures of the earthquake loading that build up with time over the duration of the ground motion, for prediction of the initiation of liquefaction. This represents the critical first step in the timing-based framework. This study used both cyclic simple shear and centrifuge testing to systematically investigate the response of liquefiable soils to fully transient earthquake loading histories. The results of these tests were used to evaluate the efficiency of evolutionary intensity measures that are typically associated with the initiation of liquefaction. In addition, observations from these tests identified key aspects of an earthquake loading history that are closely related to the generation of excess pore pressure and the initiation of liquefaction. These observations were used to develop a new evolutionary intensity measure that was able to predict the pore pressure response from the laboratory test programs more efficiently than existing intensity measures. The insights that were generated by this study offer the potential to dramatically reduce the uncertainty in the prediction of the initiation of liquefaction as compared to the conventional procedures used in current design practice.