Changes in Sand Mesostructure During Sand Reliquefaction Using Centrifuge Tests

Previous studies demonstrated that the sand reliquefaction resistance may decrease though the sand deposits were densified after reconsolidation, and attributed this counterintuitive phenomenon to the changes in sand mesostructure after liquefaction. However, no previous studies visualized how sand mesostructure evolved during the whole process of a liquefaction event. In this study, a centrifuge model of the saturated sand deposit liquefied successively under the same input seismic motion. Excess pore pressure at the upper and lower deposit were measured for assessing the sand liquefaction resistance. Besides, sand mesoscopic images during the whole process of each liquefaction event were recorded for analyzing the sand particle behaviors under multiple liquefaction events. The experimental results show that large voids formed under the upward seepage effects during sand reconsolidation, and the long-axes of the sand particles neighboring the large voids rotated vertically. The sand mesostructure after reconsolidation caused the quick contraction of the sand deposit under the subsequent shaking event.