水化针刺GCL剪切破坏机理的试验研究

土工膨润土防水毯(GCL)的内部剪切强度是影响复合防渗衬里边坡稳定性的关键因素,加筋纤维的存在使针刺GCL的内部剪切强度明显高于非加筋GCL。含水化GCL的复合防渗衬里结构剪切试验会发生应力小峰值现象,但大都被研究人员忽视;加筋纤维对GCL峰值剪切强度的贡献处于定性阶段。通过开展GCL内夹钠基膨润土的饱和剪切试验和理论分析,证实应力小峰值现象为水化针刺GCL应力位移曲线的固有特征,并且小峰值应力代表了GCL内夹膨润土的抗剪强度贡献。以应力位移曲线上的应力小峰值现象为基础,将加筋纤维对GCL峰值剪切强度的贡献定量化,结合破坏机理分析了针刺GCL内部剪切破坏和应力位移发展过程。考虑针刺GCL剪切强度各部分贡献,提出了一种能反映针刺GCL破坏机理的峰值强度准则。

Experimental research on shear failure mechanism of hydrated needle-punched GCLs

The internal face of GCLs is one of the weak interfaces within the composite impermeable liners. Their internal shear strength is enhanced by the reinforced needle-punched fiber. Through comprehensive analysis of the existing internal shear test results of needle-punched GCLs and large simple shear test results of GCL+GM composite liners, small peak stress is found to appear at small displacements in internal shear stress-displacement curves of hydrated GCLs. By conducting shear tests on hydrated GCLs-encased sodium bentonite, combined with theoretical analysis, the occurrence of the small peak stress at small displacements is confirmed to be the inherent feature in the stress-displacement curve of hydrated GCLs, and the small peak stress represents the shear strength contribution from GCL-encased bentonite. On the basis of the small peak stress phenomenon in the stress-displacement curves of needle-punched GCLs, the contribution of the reinforced fiber to the shear strength is obtained quantitatively, and the whole process of internal shear failure and stress-displacement development of GCLs is analyzed based on the failure mechanism. Considering the contribution of each part of needle-punched GCLs to the shear strength, a peak shear strength criterion model which can reflect the failure mechanism of needle-punched GCLs is proposed.