Abstract The internal shear strength of a geosynthetic clay liner (GCL) within composite liner systems is crucial for the stability of landfills and should be carefully considered in the design. To explore the shear strength and failure mechanism of the extensively used needle-punched GCL, a series of displacement-controlled direct shear tests with five normal stress levels (250–1000 kPa) and eight displacement rates (1–200 mm/min) were conducted. The shear stress to horizontal displacement relationships exhibit well-defined peak shear strengths and significant post-peak strength reductions. The monitoring results of the thickness change indicate that the degree of volumetric contraction is related to the reorientation of fibers and dissipation of pore water pressure. Furthermore, the peak and residual shear strengths both depend on the displacement rate because of the rate-dependent tensile stiffness of needle-punched fibers and shear strength of the soil/geosynthetic interface. Through additional tests and lateral comparison, it was discovered that the shear behavior of sodium bentonite, degree of hydration, and pore water pressures all affect the shear mechanisms of the NP GCL. In particular, the failure mode transfers from fiber pullout to fiber rupture with the increase in water content as the hydrated bentonite particles facilitate the stretching of needle-punched fibers.

中文翻译：

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针刺土工合成粘土衬垫的抗剪强度及破坏机理

摘要 复合衬垫系统中土工合成粘土衬垫 (GCL) 的内部剪切强度对垃圾填埋场的稳定性至关重要，在设计时应仔细考虑。为了探索广泛使用的针刺 GCL 的剪切强度和破坏机制，进行了一系列具有五个法向应力水平 (250–1000 kPa) 和八个位移速率 (1–200 mm/min) 的位移控制直剪试验。实施。剪切应力与水平位移的关系表现出明确的峰值剪切强度和峰值后强度的显着降低。厚度变化的监测结果表明，体积收缩的程度与纤维的重新定向和孔隙水压力的消散有关。此外，由于针刺纤维的拉伸刚度和土壤/土工合成材料界面的剪切强度与速率有关，因此峰值和残余剪切强度都取决于位移速率。通过额外的测试和横向比较，发现钠基膨润土的剪切行为、水化程度和孔隙水压力都会影响 NP GCL 的剪切机制。特别是，随着含水量的增加，失效模式从纤维拉出转变为纤维断裂，因为水合膨润土颗粒促进了针刺纤维的拉伸。水化程度和孔隙水压力都会影响 NP GCL 的剪切机制。特别是，随着含水量的增加，失效模式从纤维拉出转变为纤维断裂，因为水合膨润土颗粒促进了针刺纤维的拉伸。水化程度和孔隙水压力都会影响 NP GCL 的剪切机制。特别是，随着含水量的增加，失效模式从纤维拉出转变为纤维断裂，因为水合膨润土颗粒促进了针刺纤维的拉伸。