大型斜面剪切仪的研制和试验

Development and tests of large-scale inclined direct shear apparatus

位于垃圾填埋场斜坡上的衬垫结构在垂直应力作用下沿斜坡滑移的剪切状态与底坡上衬垫结构的不同,为了模拟斜坡上衬垫结构间剪切特性,研制了斜面剪切仪。通过对标准砂和黏土的大型斜面和普通直剪剪切试验,发现两种试验得到的标准砂和黏土剪切应力位移特性基本相同,强度指标也相同。在此基础上,进行了光面HDPE土工膜与黏土复合衬垫界面斜面剪切试验,得到的剪应力与正应力比–位移曲线均有峰值和峰值后的软化现象。斜面剪切试验的特点是能够得到剪切面上法向应力和剪切应力同时增加的变化规律,可以揭示更详细的剪切特征,这有利于分析剪切过程中剪切面上法向应力和剪切应力的特性,如剪切面上法向应力和剪切应力变化规律以及剪切面上法向应力和剪切应力比的变化规律。

The shearing status for the landfill liner system located on the slope is different from that located on the bottom floor. A large-diameter inclined direct shear apparatus is designed to simulate liner shearing on various slopes. The comparative tests between the inclined and traditional direct shear apparatuses are conducted using the standard sand and the selected clay. It is found that both the displacement behavior and the shear strength of the standard sand and the selected clay obtained fi-om the inclined and traditional direct shear tests are basically the same. More inclined shear tests are conducted for a composite liner interface between smooth HDPE geomembrane and compacted clay. All curves of the ratio of shear to normal stresses vs. the displacement under various vertical pressures show strain-softening behavior in the inclined shear test. The advantage of the inclined shear test is that more detailed shearing characteristics regarding changes of the normal and shear stresses on the shearing plane and the ratio of the shear to normal stresses can be investigated.