复合土工膜-不同含水率垫层结构界面直剪摩擦特性试验研究

Experimental study on interface direct shear friction characteristics of composite geomembrane and cushion with different moisture content

复合土工膜-垫层防渗体作为一种刚柔混合防渗结构体系,其界面摩擦特性对工程的安全运行至关重要。为给复合土工膜防渗体在特大流量引水渠道工程中的应用提供科学合理的依据,探析复合土工膜-垫层界面摩擦特性和界面强度特性,重点考虑膜后垫层材料含水率的变化,采用室内直剪试验对复合土工膜与不同含水率0%、3%、6%、8.5%垫层材料的摩擦剪切特性进行研究,分析不同含水率工况下的界面强度特性。结果表明:复合土工膜与不同含水率垫层材料的界面剪切特性经历了弹性、弹塑性和残余强度阶段,具有明显的峰值强度和残余强度特征,剪切位移为9~11 mm时达到峰值强度。随着剪切位移的增大,界面剪应力先减小后逐渐趋于稳定,表现出稳定的残余强度,残余强度约为峰值强度的80%~90%。随着垫层材料含水率增大,界面峰值抗剪强度和残余抗剪强度呈非线性减小趋势,表明膜后垫层材料水分对界面强度具有“润滑效应”。

As a rigid and flexible composite geomembrane-cushion impervious structure,the interface friction characteristics of the composite geomembrane-cushion impervious structure are very important to the safe operation of engineering.To provide a scientific and reasonable basis for the application of composite geomembrane impermeability in the engineering of large flow diversion channel,explore the interface friction characteristics and interface strength characteristics of composite geomembrae-bedding,the change of water content of bedding material behind the membrane was mainly considered,the indoor direct shear test was conducted to study the friction shear characteristics of composite geomembrae-bedding material with different water content(0%,3%,6%,8.5%),and the interface strength characteristics under different water content conditions were discussed.The results show that the interfacial shear properties of composite geomembranes and bedding materials with different water content go through elastic,elastoplastic and residual strength stages,and have obvious peak strength and residual strength characteristics.The peak strength is reached when the shear displacement is 9~11 mm.With the increase of shear displacement,the shear stress at the interface decreases first and then tends to be stable,showing a stable residual strength,which is about 80%~90%of the peak strength.The peak shear strength and residual shear strength at the interface showed a nonlinear decreasing trend with the increase of the moisture content of the bedding material,indicating that the moisture content of the bedding material behind the film had a"lubricating effect"on the interface strength.