Previous studies have revealed that past shaking can substantially affect sand reliquefaction resistance. Researchers have attributed these effects to the formation of stable or vulnerable sand mesostructures during previous shaking events. However, no experiment has been performed to directly visualize how sand particles evolve into stable or vulnerable mesostructures. In this study, a sand deposit was shaken by four repeated seismic motions in centrifuge model tests, and simultaneously, mesoscopic images of sand particles were recorded by a newly developed microimage acquisition system. The mesoscopic images showed that pore fluid seepage caused particles previously in contact to be separated and form large voids during sand reconsolidation stages. The sand with large voids quickly contracted during the subsequent shaking event, exhibiting a decreasing sand reliquefaction resistance. The sand reliquefaction resistance gradually increased as the seepage damage effects attenuated, and the number of sand particle contacts increased with sand densification under multiple shaking events. The testing results suggested that influences of the excess pore pressure dissipation on the sand mesostructure should be considered in assessing sand reliquefaction resistance.

先前的研究表明，过去的震动会显着影响沙子的再液化阻力。研究人员将这些影响归因于之前的震动事件中稳定或脆弱的沙子细观结构的形成。然而，尚未进行任何实验来直接可视化沙粒如何演变成稳定或脆弱的细观结构。在这项研究中，在离心机模型测试中，砂层被四次重复的地震运动震动，同时，砂粒的细观图像由新开发的显微图像采集系统记录。细观图像显示，孔隙流体渗漏导致先前接触的颗粒在砂岩再固结阶段分离并形成大空隙。大空隙的沙子在随后的震动事件中迅速收缩，表现出降低的砂再液化阻力。砂土再液化阻力随着渗流损伤效应的减弱而逐渐增加，砂粒接触次数随着多次震动作用下砂土的致密化而增加。试验结果表明，在评估砂土再液化阻力时，应考虑超孔隙压力消散对砂土细观结构的影响。