Evaluation of dynamic behavior of shallow foundation through soil-foundation-structure-interaction in liquefied soil using centrifuge modeling

Abstract

Liquefaction can occur in saturated and loose soils and cause catastrophic damage accompanied with ground settlement and rotation of superstructures. Structures on liquefied soils are exposed to the volumetric-induced settlement, deviatoric-induced settlement, and soil ejecta (sand boil). However, ground deformation mechanisms associated with soil-foundation-structure interaction (SFSI) remains poorly understood. Therefore, this dissertation aims to observe the dynamic and settlement behaviors of liquefiable soils during earthquake loading, to evaluate the effect of structural load and earthquake duration on dynamic behavior of a shallow foundation and associated ground settlement, and to examine the effect of sequential liquefaction triggers on dynamic behavior of a shallow foundation and associated ground settlement, through dynamic centrifuge modelling. The centrifuge experiment results show clear evidences of liquefaction and associated ground settlement in free-field ground without a foundation. By contrast, the ground under a foundation shows the ratio of pore water pressure (Ru) less than unity, but with a more significant deformation due to its overlying structural weight. It is found that the earthquake duration has a profound effect on the settlement of an overlying structure rather than the peak amplitude of earthquake. As the first earthquake induces a small rotation of a structure, the after-shock earthquake exacerbates and causes more severe rotations of the structure though it causes less settlement due to the reduced void ratio and the foundation embedment effect. Among the intensity measures, the cumulative absolute velocity (CAV) shows a good correlation with the settlement. The presented study provides clear physical modeling result that advances our understanding on the dynamic characteristics of the soil-foundation-structure interaction (SFSI) during earthquakes in the liquefied ground through centrifuge experiment.