黄河口粉质土海床液化过程的现场试验研究

In-situ test to study silt liquefaction at the subaqueous delta of Yellow River

在黄河口海床若干深度处埋设孔压探头,海床表面利用活塞施加水压循环荷载以模拟波浪荷载,观测土体内孔隙水压力变化过程,研究黄河口原状和重塑粉质土在波浪循环荷载作用下的液化特征。通过研究发现,原状土和重塑土的孔压激发曲线模式不同,原状土孔压经历四个阶段,即先上升、后下降、再上升和剧烈波动;而重塑土孔压只有上升和剧烈波动两个阶段,这两种模式与循环荷载作用下粉土的微结构变化有关。分析波浪荷载的特点,将孔压出现剧烈波动的时刻作为完全液化的标志。土体液化与固结程度有关,固结程度越大,越不易液化。实际波浪荷载作用下,土体液化时间比文中试验测得的要短。

An In-situ water-pressure test was performed at the subaqueous delta of Yellow River for studying the undisturbed and rebuilt silty soil liquefaction responses, by planting pore pressure probes at several depths and using pistons to put cyclic pressure on the seabed. During the test, pore water pressure variation was observed. The pore pressure variation of undisturbed and rebuilt silty soil showed different patterns. The undisturbed soil experienced four stages, namely the first rise, after the fall, then rise and volatility; however the rebuilt soil only had the last two stages, rise and volatility. These two patterns were controlled by the silt micro-structure changes under cyclic loading. The moment of volatility should be taken as an indicator of complete liquefaction induced by wave. The liquefaction was influenced by consolidation degree, the higher the degree of consolidation, the more difficult for liquefaction. The liquefaction time under actual wave was shorter than those measured at the test.