An investigation of repeated liquefaction resistance of clayey sand by element test

Soil liquefaction poses a significant risk to both human lives and property security. Recent in-situ cases have shown that clayey sand can experience multiple liquefaction events during mainshock-aftershock sequences, known as repeated liquefaction. While existing studies have focused on the cyclic behavior of initial liquefaction events, there is a lack of research on the mechanisms and cyclic response of repeated liquefaction in clayey sand. The factors that control repeated liquefaction in clayey sand are still not fully understood. In this study, a series of cyclic triaxial tests were conducted on sand with varying clay content (0 %, 5 %, 10 %, 15 %, and 20 %) under earthquake sequences. The test results showed that the liquefaction resistance initially decreased significantly and then increased with the number of liquefaction events. Sands with higher clay content exhibited earlier recovery of resistance during continuous liquefaction events. The analysis of the test results revealed that the repeated liquefaction resistance of clayey sand was quite intricate. Sands with a relative density (after reconsolidation) below 80 % were primarily influenced by the degree of stress-induced anisotropy, while sands with a relative density above 80 % were mainly affected by relative density.