Abstract This study investigates how the shear rate can affect the geomembrane – protective geotextile friction angle. Four types of geomembranes (GMB) were considered (EPDM, HPDE, PP, and PVC) and a single nonwoven needle-punched geotextile (GTXnw) was used to make the interfaces with the geomembrane. Three shear devices were used: a large-scale inclined plane (IP), a shear box (SB), and a small-scale shear device (ssSD). The ssSD allows two shear modes to be compared: one mode involves incrementally increasing the shear stress, and the other involves imposing a constant tangential velocity at the interface. Only the PP GMB- GTXnw was tested with the SB and the ssSD. Inclined plane standardised tests show that for the three interfaces that undergoes gradual sliding (EPDM, PP and PVC GMB- GTXnw), it is shown that a step-by-step experimental procedure gives significantly lower interface friction angle than that given by the procedure from the current international standard, which is explained by the increase of interface shear stress with sliding speed. These observations are confirmed by shear box tests. One major practical result is that, following the nature of geosynthetics, the shear rate applied in large-scale shear box tests should be adapted to assess a safety value of a geosynthetic - geosynthetic interface friction angle.

中文翻译：

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土工膜的测定 - 保护性土工布摩擦角：对剪切速率效应的洞察

摘要 本研究研究了剪切速率如何影响土工膜-保护土工布摩擦角。考虑了四种类型的土工膜 (GMB)（EPDM、HPDE、PP 和 PVC），并使用一种非织造针刺土工布 (GTXnw) 来制作与土工膜的界面。使用了三种剪切装置：大型斜面 (IP)、剪切箱 (SB) 和小型剪切装置 (ssSD)。ssSD 允许比较两种剪切模式：一种模式涉及逐步增加剪切应力，另一种涉及在界面处施加恒定的切向速度。只有 PP GMB-GTXnw 与 SB 和 ssSD 一起进行了测试。斜面标准化试验表明，对于逐渐滑动的三个界面（EPDM、PP和PVC GMB-GTXnw），结果表明，分步实验程序给出的界面摩擦角明显低于当前国际标准程序给出的界面摩擦角，这可以通过界面剪切应力随滑动速度的增加来解释。这些观察结果通过剪切盒试验得到证实。一个主要的实际结果是，根据土工合成材料的性质，应调整在大型剪切箱试验中应用的剪切速率，以评估土工合成材料-土工合成材料界面摩擦角的安全值。