冲击作用下饱和土性状的试验研究

在三轴条件下,对饱和土（砂土和黏土）进行排水与不排水条件下的冲击试验及冲击后再固结试验,对比研究了不同渗透性土在不同排水条件下的冲击动力响应和冲击后再固结性状。结果表明：饱和黏土不排水冲击时的孔隙水压力随冲击击数增加而升高并逐渐稳定,排水冲击时的孔隙水压力则是先达到峰值然后有所下降;砂土不排水冲击时的冲击能量对孔隙水压力影响最明显;饱和砂土不排水冲击时的轴向应变与冲击击数呈近似线性关系,饱和黏土冲击及饱和砂土排水冲击则呈近二次曲线关系;饱和砂土不排水冲击后再固结阶段的孔隙水压力立即消散为0,同时体变迅速增大到一定值;饱和黏土在冲击后再固结阶段的孔隙水压力在一定时间内逐渐消散完毕,同时体变逐渐增大;饱和黏土排水冲击时,冲击阶段产生的体变占冲击引起总体变的39%～49%,冲击后再固结阶段产生的体变占51%～61%;砂土和黏土的总体变均表现为排水冲击明显大于不排水冲击,改善冲击时的排水条件有利于提高加固效果。

Laboratory Research on the Saturated Soil Behavior Under Impact

Under the triaxial condition, tests of impact and reconsolidation after impact were conducted on saturated sand and clay with the drained and undrained conditions respectively; the dynamic response to impact and behavior of reconsolidation after impact under different drainage conditions for the soils with different penetrability were comparatively investigated. The results showed that the pore water pressure of saturated clay increased with blow number, and then gradually trended to be stable under undrained condition, while it dropped after reaching a peak under drained condition; impact energy had most significant influence on pore water pressure for sand under undrained condition; relationship between axial strain and blow number of saturated sand was approximately linear under undrained condition, while it was nearly quadratic for saturated sand under drained condition and saturated clay; pore water pressure immediately decreased to zero for saturated sand during reconsolidation after impact under undrained condition, and volumetric change instantly increased to a certain value; pore water pressure gradually decreased to zero within a given period for saturated clay during reconsolidation after impact under undrained condition, and volumetric change gradually increased; the volumetric changes of saturated clay during impact were 39%-49% of total volumetric changes, and the volumetric changes during reconsolidation after impact were 51%-61%; total volumetric changes for sand and clay under drained condition were larger significantly than that under undrained condition, and improving the drainage condition was favorable to increase reinforcement effect.