Evolution Process of Sand Mesostructure in Liquefaction Using Centrifuge Shaking Table Tests

Previous studies suggested that earthquake liquefaction events would change sand mesostructure, which was also a critical factor affecting the mechanical properties of the reconsolidated sand. However, few studies have directly visualized the evolution of sand mesostructure during liquefaction. In this study, an inflight micro-image acquisition system was designed, developed, and applied to obtain sand particle images of a saturated sand deposit during the whole process of seismic liquefaction based on centrifuge shaking table tests. Excess pore pressure, acceleration and ground displacement were also measured simultaneously. Experimental results show that the beginning small-amplitude shaking increased the interparticle contacts and decreased the voids among particles. The interparticle contacts were reconstructed and the voids were redistributed along with the later larger-amplitude shaking. After liquefaction, the upper seepage of the pore fluid contributed to the expansion of large voids in the approximately vertical and horizontal direction. Sand particles rotated towards vertical under the upward pore fluid seepage. The drastic changes in the sand mesostructure during liquefaction may be the intrinsic mechanism that influenced sand reliquefaction resistance.