垃圾填埋场复合衬垫剪切特性单剪试验研究

Shearing behavior of landfill composite liner by simple shear test

针对垃圾填埋工程中复合衬垫的界面抗剪特性,利用改进的叠环式单剪仪,对由砂土-无纺型土工布-土工网格-土工膜-夯实粘土组成复合衬垫进行了整体剪切试验研究。重点讨论了复合衬垫整体单剪试验的应力-位移曲线、相同剪切应力下各个界面的位移大小与变化特征和强度特性。研究结果表明:复合衬垫整体单剪试验的应力-位移曲线在低法向应力试验中没有呈现明显的软化特征,在高法向应力试验中有硬化现象;随法向应力增加剪切破坏面会发生转移;目前常用的把复合衬垫拆分为单个界面进行研究来确定最危险界面的方法不能够正确地反映填埋场中的复合衬垫在加载过程中的衬垫单元的实际受压变形情况和在剪切变形过程中最危险破坏面转移的情况;复合衬垫界面的抗剪强度包线呈现双曲线性质。

The scope of this paper is to investigate shearing behavior of landfill composite liner by using ring simple shear apparatus to conduct integrated shearing test for the composite liner system. The composite liner used in the tests consists of sand layer, nonwoven geotextile, geonet, HDPE geomembrane and compacted clay. From the test results, it can be found that the relationship between shear stress and displacement of a composite liner does not show a softening behavior under a low normal pressure and however, it shows a hardening behavior under a high normal pressure. The critical failure interface with the largest displacement in a composite liner is not fixed at a single interface, and it can shift from one to another with changes of normal pressure. Thus, the conventional research method for the composite liner systems, which is to conduct liner interface test separately to find a single weakest interface, cannot simulate the true shearing behavior for a composite liner system in landfill. The strength envelop of a composite liner can be simulated by a hyperbolic model.