Centrifuge and Numerical Models to Investigate Liquefaction-Induced Response of Shallow Foundations with Different Contact Pressures

Abstract

Currently, there is no reliable design procedure which considers all aspects of liquefaction effects on shallow foundations. There are many light and heavy structures resting on saturated sand with high liquefaction potential in seismic areas. The aim of this experimental and numerical study is to evaluate the performance of two shallow foundations with different contact pressures in liquefaction. The results of the centrifuge experiment of shallow foundations with surcharges of three-story and nine-story buildings on liquefiable sand are presented in detail. Although entire soil profile is liquefied, no liquefaction is observed under the foundations. There is a clear difference in settlement mechanisms observed beneath the shallow foundation and in the free-field. The heavy foundation fluctuated more strongly compared with the lighter one. The effect of soil permeability and contact pressure on foundation response is investigated during numerical study. Subsequently, the experiment is simulated two dimensionally using a fully coupled nonlinear constitutive model (UBCSAND) implemented in a finite-difference program, FLAC-2D. The results show that settlement of foundations increased with the increase of soil permeability. Trends of excess pore water pressure are captured reasonably by the soil model, but the settlement mechanisms are different. The soil model underestimates total liquefaction-induced settlement of shallow foundation, especially for light foundation.