地震历史对砂土抗液化性能影响的试验研究

为探讨地震历史对饱和砂土抗液化性能的影响，通过离心机动力模型试验，观测了遭受过不同强度地震的饱和砂土水平场地在再次地震荷载作用下的响应，包括超静孔隙水压力的发展和土体的变形。研究表明，小地震有利于增强砂土颗粒之间的咬合及结构的稳定性，极大地提高了其抗液化能力，而遭受强地震并且发生液化的砂土，由于在沉积过程中形成的不稳定结构，则可能在将来强度相对较小的地震中再次液化。试验结果说明了地震历史对砂土液化性能有重大影响及进一步开展砂土细观结构研究的重要性。

Centrifuge investigation on effect of seismic history on resistance of sand to liquefaction

To investigate the effect of seismic history on the liquefaction resistance of sand, two groups of centrifuge dynamic tests have been performed on models of saturated sand deposit. The response of excess pore pressure as well as deformation of soil column were monitored and recorded during testing. It was found that small earthquake could bring beneficial effect on the sand resistance to liquefaction by strengthening interlocking between particles and forming a more stable structures. On the other hand, re-liquefaction may occur on a once liquefied site when it is subjected to an earthquake with magnitude less than that causes the first liquefaction, due to the unstable structure formed in the re-sedimentation process. The experimental finding indicates the impact of seismic history on the liquefaction characteristics of sand, as well as the significance of study on microstructure of sand.