面膜堆石坝不同品种土工膜力学特性

Mechanical properties of different geomembranes in membrane-faced rockfill dam

针对面膜堆石坝主体防渗材料常用的几个品种土工膜力学性能,展开了土工膜单向拉伸、液胀、耐局部划痕损伤和适应颗粒垫层变形能力的试验性研究。试验分析成果表明:1.0 mm厚的膜材中PVC-HX膜的杨氏模量、应力应变线弹性区间和适应变形能力方面具有一定优越性;划痕长度、方向和深度占膜厚比值相同的条件下,TPO膜耐局部划痕损伤能力较强,PVC-HX膜仍展现良好的耐损伤极限强度和极限延伸率,能够满足膜防渗结构力学性能要求;厚度大于0.8mm的HDPE/PE膜刚度偏大,适应变形和耐局部划痕损伤能力偏低,不适用于高水头压力下多孔隙介质垫层的膜防渗结构。试验成果分析表明膜厚大于1.0mm的PVC-HX膜和TPO膜在高面膜堆石坝膜防渗结构中应用具有潜在优势,工程设计厚度不大于0.8 mm的土工膜可优先选择HDPE/PE膜。

Aiming at the mechanical properties of several geomembranes(GMs)commonly used as the main impervious materials of membrane-faced rockfill dam(MFRD),the uniaxial tensile tests,liquid expansion tests,local scratch resistance tests and capability to accommodate deformation tests are carried out.The test results show that compared to other GMs,the PVC-HX with the thickness of 1.0 mm is superior in the Young's modulus,linear elastic range of stress-strain and capability to accommodate deformation.Under the same scratch length,direction and ratio of depth to thickness,the TPO has strong resistance to the local scratch damage.However,the PVC-HX behaves satisfactorily in the ultimate strength against damage and the ultimate elongation,which can meet the mechanical performance requirements of impervious structures of the GMs.The HDPE/PE with thickness greater than 0.8 mm has high stiffness,low capability to accommodate deformation and local scratch damage,therefore,it is not suitable for the impervious structures of the GMs under high pressure and porous medium cushion.The comprehensive results indicate that the PVC-HX and TPO with thickness greater than 1.0 mm have potential advantages in the impervious structures of high MFRDs,and the HDPE/PE is recommended when the thickness is less than 0.8 mm required in engineering design.