Centrifuge Testing to Evaluate and Mitigate Liquefaction-Induced Building Settlement Mechanisms

TLDR

Understanding liquefaction development and consequences is essential for effective mitigation. Centrifuge tests on rigid‑mat foundations over thin liquefiable sand examined dominant settlement mechanisms and evaluated how mitigation measures reduce their contributions. Settlement importance varies with earthquake motion, soil, and building, with shaking rate strongly controlling initiation, rate, and amount; design should use shaking intensity rate, and stiff perimeter walls cut settlements by ~50%, while flexible barriers provide smaller reductions.

Abstract

The effective application of liquefaction mitigation techniques requires an improved understanding of the development and consequences of liquefaction. Centrifuge experiments were performed to study the dominant mechanisms of seismically induced settlement of buildings with rigid mat foundations on thin deposits of liquefiable sand. The relative importance of key settlement mechanisms was evaluated by using mitigation techniques to minimize some of their respective contributions. The relative importance of settlement mechanisms was shown to depend on the characteristics of the earthquake motion, liquefiable soil, and building. The initiation, rate, and amount of liquefaction-induced building settlement depended greatly on the rate of ground shaking. Engineering design procedures should incorporate this important feature of earthquake shaking, which may be represented by the time rate of Arias intensity (i.e., the shaking intensity rate). In these experiments, installation of an independent, in-ground, perimetrical, stiff structural wall minimized deviatoric soil deformations under the building and reduced total building settlements by approximately 50%. Use of a flexible impermeable barrier that inhibited horizontal water flow without preventing shear deformation also reduced permanent building settlements but less significantly.