The role of cohesion and overconsolidation in submarine slope failure
The role of cohesion and overconsolidation in submarine slope failure
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DOI：
10.1016/j.margeo.2015.08.012
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发表时间：
2015-11-01
期刊：
影响因子：
2.9
通讯作者：
Kopf, Achim J.
中科院分区：
文献类型：
--
作者：
Ikari, Matt J.;Kopf, Achim J.
海底边坡破坏的安全系数分析主要取决于边坡材料的剪切强度，通常用剩余强度值和正常固结的沉积物来评估剪切强度。在这里，我们报告了在各种超固结比 (OCR) 下对石英粘土混合物的剪切强度和内聚力的直接测量。对于低应力下通常固结的沉积物，与摩擦相比，内聚力是剪切强度的主要来源。当 OCR > 4 时，峰值剪切强度显着增加，这种强度增加的主要原因是内聚力增加，而不是摩擦力增加。由于内聚力而增加的剪切强度的比例与 OCR 成对数线性关系。我们表明，在 OCR 值较高的浅层深度，超固结粘土可能比纯或近乎纯的石英沉积物更强，后者在近地表条件下是无粘性的。我们的数据还表明，由于先前的质量运动而经历过严重脱顶的区域，由于峰值强度增加，不太可能在浅深度发生后续故障，并且如果发生故障，预计 OCR 较低的地方会更深。在地震活跃地区，与当地地震引发的预期触发率相比，这是对普遍观察到的斜坡失稳复发率较低的一种可能解释。 (C) 2015 Elsevier B.V. 保留所有权利。
Factor-of-safety analyses of submarine slope failure depend critically on the shear strength of the slope material, which is often evaluated with residual strength values and for normally consolidated sediments. Here, we report on direct measurements of both shear strength and cohesion for a quartz-clay mixture over a wide range of overconsolidation ratios (OCRs). For normally consolidated sediment at low stresses, cohesion is the dominant source of shear strength compared to friction. Significant increases in peak shear strength occur for OCR > 4, and the primary source of this strength increase is due to increased cohesion, rather than friction. The proportion of added shear strength due to cohesion depends log-linearly on the OCR. We show that at shallow depths where OCR values can be high, overconsolidated clays can be stronger than pure or nearly pure quartz sediments, which are cohesionless under near-surface conditions. Our data also suggest that areas which have experienced significant unroofing due to previous mass movements are less likely to experience subsequent failure at shallow depths due to increased peak strength, and if failure occurs it is expected to be deeper where the OCR is lower. In seismically active areas, this is one potential explanation for the general observation of lower slope failure recurrence compared to rates expected from triggering due to local earthquakes. (C) 2015 Elsevier B.V. All rights reserved.