The role of sediment composition and behavior under dynamic loading conditions on slope failure initiation: a study of a subaqueous landslide in earthquake-prone South-Central Chile
The role of sediment composition and behavior under dynamic loading conditions on slope failure initiation: a study of a subaqueous landslide in earthquake-prone South-Central Chile
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DOI：
10.1007/s00531-015-1144-8
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发表时间：
2015-01
影响因子：
2.3
通讯作者：
G. Wiemer;J. Moernaut;N. Stark;P. Kempf;M. Batist;Mario Pino;R. Urrutia;Bruno Ladrón de Guevara;M. Strasser;A. Kopf
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文献类型：
--
作者：
G. Wiemer;J. Moernaut;N. Stark;P. Kempf;M. Batist;Mario Pino;R. Urrutia;Bruno Ladrón de Guevara;M. Strasser;A. Kopf
水下滑坡的破坏机制目前仍不甚清楚，部分原因是由于海底滑坡的位置较远，研究难度较大。湖泊中的滑坡规模较小，更容易接近，因此是一种很好的替代海洋滑坡的方法。维拉里卡湖位于智利中南部，经历了严重的斜坡破坏，是构造活跃背景下水下滑坡引发机制的典范研究区。取心和CPTU测试是用部署在取心地点附近的MARUM自由落体CPTU进行的，在那里采样了涉及斜坡破坏的所有岩性单位。采用拟静力安全系数分析和循环三轴试验等岩土工程方法，分析了硅藻土、火山灰和速冻粘土三种类型的土体在边坡破坏中的作用，确定地震震动是其主要触发机制。所调查的滑坡由两个截然不同的阶段组成。在第一阶段中，坡体破坏是在一片片土层之上开始的。在第二阶段，海退导致滑崖沿位于地层更深、极敏感的岩性(即快速粘土)中的第二断层面向岸边延伸。结果表明，埋藏的陀螺层不太可能发生液化，但这样的层仍可能导致与邻近沉积物接触区域的抗剪强度降低。此外，硅藻胶泥中的周期性振动引起的孔压可能类似于颗粒土中的孔压。我们通常推断，这项研究中观察到的破坏机制对海底环境下的滑坡启动同样重要，因为活动大陆边缘可能大量存在与火山灰夹层的硅藻软泥。
Subaqueous slope failure mechanisms are still poorly understood partly because they are difficult to study due to the remote location of submarine landslides. Landslides in lakes are smaller in size and more readily accessible and therefore represent a good alternative to their marine counterparts. Lake Villarrica, located in South-Central Chile, experienced significant slope failure and serves here as an exemplary study area for subaqueous landslide initiation mechanisms in tectonically active settings. Coring and CPTU testing were undertaken with the MARUM free-fall CPTU deployed adjacent to the coring sites where all lithological units involved in the slope failure were sampled. Using geotechnical methods such as pseudo-static factor of safety analysis and cyclic triaxial testing, three types of soils (i.e., diatomaceous ooze, volcanic ash, and quick clay) were analyzed for their role in slope failure, and earthquake shaking was identified as the primary trigger mechanism. The investigated landslide consisted of two distinct phases. During the first phase, slope failure was initiated above a tephra layer. In the second phase, retrogression led to the shoreward extension of the slide scarp along a second failure plane located in a stratigraphically deeper, extremely sensitive lithology (i.e., quick clay). Results show that liquefaction of buried tephra layers was unlikely, but such layers might still have contributed to a reduction in shear strength along the contact area with the neighboring sediment. Furthermore, cyclic shaking-induced pore pressure in diatomaceous ooze may be similar to that in granular soils. We generally infer that failure mechanisms observed in this study are equally important for landslide initiation in submarine settings as diatomaceous ooze intercalated with volcanic ash may be abundantly present along active continental margins.