Progressive shear-surface development in cohesive materials; implications for landslide behaviour
Progressive shear-surface development in cohesive materials; implications for landslide behaviour
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DOI：
10.1016/j.enggeo.2014.05.009
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发表时间：
2014-07
影响因子：
7.4
通讯作者：
J. Carey;D. Petley
中科院分区：
文献类型：
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作者：
J. Carey;D. Petley
本研究的目的是调查机制的渐进剪切面发展，使用一系列专门的三轴单元测试。对英格兰南部怀特岛上文特诺悬崖下的高尔特粘土的完整和重塑样品进行了三轴孔压再膨胀（PPR）试验，其中破坏是在恒定的总应力状态下通过增加孔压产生的。此外，还进行了一项新的长期（> 500天）蠕变试验，在该试验中，样品最终在低于破坏包络线的恒定应力状态下破坏。试验表明，未受扰动的高尔特粘土样品以脆性方式破坏，使用Saito技术绘制时产生线性趋势。另一方面，重塑样品表现出韧性行为，如由非线性斋藤趋势所示。进行了一些其他相同的PPR试验，其中孔隙水压力的增加率是不同的。这些试验表明，在PPR试验中任何点产生的应变速率取决于有效应力和有效应力的变化率。后者很重要，因为应力的变化会产生应变的变化。因此，虽然在不同有效应力变化率下的试验在q-p′空间和应变-p ′空间中绘制时相似，但它们在应变率-p ′空间中明显不同。当应力状态保持恒定超过80天时，长期蠕变试验失败。这种机制是让人想起蠕变断裂，发生以下的故障包络线定义在常规experiments.We得出结论，第一次失败的高尔特粘土是一个渐进的机制为主的发展微裂纹，导致应变局部化和发展的一个或多个剪切面在故障。虽然这种机制通常可能会发生在压力变化的反应中，但研究表明，失败可以逐步发展。在重塑高尔特粘土剪切应变不能本地化沿着一个奇异的剪切surfaces.The结果提供了新的见解滑坡运动的机制内运作的文特诺滑坡复杂，并表明，目前的运动很可能发生在一个预先存在的剪切面。实验室测试表明，这种材料不太可能发生灾难性的故障。
The aim of this study was to investigate mechanisms of progressive shear surface development using a series of specialised triaxial cell tests. Intact and remoulded samples of Gault Clay from the Ventnor Undercliff on the Isle of Wight in southern England were subjected to pore pressure reinflation (PPR) testing in a triaxial cell, in which failure is generated by increasing pore pressure under a constant total stress state. In addition, a novel very long term (> 500 days) creep test was undertaken, in which the sample eventually failed at a constant stress state below the failure envelope.The experiments showed that undisturbed samples of the Gault Clay failed in a brittle manner, generating a linear trend when plotted using the Saito technique. On the other hand, remoulded samples showed ductile behaviour, as indicated by a non-linear Saito trend. A number of otherwise identical PPR tests were conducted in which the rate of increase in pore water pressure was varied. These tests showed that strain rate generated at any point in the PPR tests depended on both the effective stress and the rate of change of effective stress. The latter is important because a change in stress generates a change in strain. Thus, whilst tests at different rates of change of effective stress are similar when plotted in q–p′ space and in strain–p′ space, they are markedly different in strain rate–p′ space.The long term creep test failed when the stress state had been constant for over 80 days. This mechanism was reminiscent of creep rupture, occurring below the failure envelope defined in the conventional experiments.We conclude that first time failure in the Gault Clay is a progressive mechanism dominated by the development of micro-cracking, which leads to strain localisation and the development of one or more shear surfaces at failure. Whilst this mechanism may usually occur in response to a change in stress, the study indicates that failure can develop progressively. In the remoulded Gault Clay shear strains cannot localise along a singular shear surface.The results provide new insight into the mechanisms of landslide movement operating within the Ventnor landslide complex and indicate that present movements are likely to be occurring on a pre-existing shear surface. The lab tests suggest that this material is unlikely to undergo catastrophic failure.