压实粘性土三轴拉伸试验研究

对于岩土材料而言,在相同的压力下(应力张量第一不变量I1)的三轴拉伸强度与三轴压缩强度相比,在较低的偏应力下发生破坏,这说明岩土材料的强度明显依赖于偏应力张量第三不变量J3,而常用莫尔-库仑准则虽然能够反映在相同的压力下三轴拉伸与压缩强度的差异性,但其比值Q2与压力无关.通过三轴压缩和三轴拉伸试验,对主应力差和比值Q2随压力的变化进行了研究,结果表明:在一定压力范围内,主应力差与围压的关系为线性关系；在低围压(指使试样发生剪切破坏的最小围压),测试获得的主应力差值与摩尔-库伦公式计算值相当,但随着围压的增加,两者差值增加,且计算所得的主应力差均大于测试值；在一定范围内,比值Q2随压力(应力张量第一不变量I1)呈线性指数递减变化；同时在较低压力下,三轴拉压强度比值与利用莫尔-库仑准则计算的数值相当.

Experimental research on triaxial extension of compacted clay

For geo-materials,under the same pressure failure occurs at lower deviator stress in TXE than in TXC,which indicates that the strength of soils strongly depends on the third invariant of stress deviatorJ3.Although the traditional Mohr-Coulomb criterion can differentiate the strength of TXE from that of TXC under the same pressure,the pressure is irrelevant to the strength ratio Q2.In this paper,changes of deviator stresses and ratio Q2 with pressures were studied by means of TXC and TXE.It is found: Within certain range,the deviator stresses increase with confining pressures in linear manner,under lower confining pressures(the minimum pressure which causes sample to fails in TXE),the deviator stresses measured are close to those by Mohr-Coulomb equation,but difference between them increases with increasing confining pressure and the calculated values by Mohr-Coulomb equation are always larger than the measured ones;Within certain range ratio Q2 with pressures decrease in linear-Exponential manner;and concurrently,in the lower pressure the strength ratios Q2 of TXE and TXC are comparable with those obtained by Mohr-Coulomb equation.