Mechanisms of rainfall-induced landslides in gently inclined red beds in the eastern Sichuan Basin, SW China
Mechanisms of rainfall-induced landslides in gently inclined red beds in the eastern Sichuan Basin, SW China
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DOI：
10.1007/s10346-015-0611-4
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发表时间：
2015-07
期刊：
影响因子：
6.7
通讯作者：
Ming Zhang;Yue-ping Yin;Bolin Huang
中科院分区：
文献类型：
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作者：
Ming Zhang;Yue-ping Yin;Bolin Huang
红层在四川盆地东部广泛分布，常被称为“滑坡易发层”。这些红层的倾角一般小于10°，远小于层面间的内摩擦角。因此，在理论上，破坏不会发生沿着层面在这样的地层。以西南地区的青宁滑坡为例，采用野外调查、数值模拟和环剪试验相结合的方法，研究了降雨对浅倾红层滑坡的影响。研究结果表明，滑坡体破坏的可能机制是：（1）降雨通过滑坡体后部裂隙的渗透，增加了静水压力，增加了滑动应力，降低了滑动面上的有效应力，使滑坡体逐渐失稳。在庆宁滑坡中，滑坡破坏前最大水压力高达21.8m。当安全系数显著下降到1.015时，滑体开始缓慢滑动。(2)滑动发生时，滑带土处于不排水剪切状态，其抗剪强度急剧下降到临界值，从而促进了快速滑动。在庆宁滑坡中，当孔隙水压力增加到118.3kPa时，滑带土的抗剪强度显著下降到25.9kPa。该研究可为四川盆地东部缓倾斜红层滑坡的预测预报提供理论依据。
Red beds are widespread in the eastern Sichuan Basin, SW China, and are often called “landslide prone strata”. The dip angle of these red beds is commonly less than 10°, which is much less than the angle of internal friction between the bedding planes. Thus, in theory, failure will not occur along the bedding planes in such strata. We used field methods, numerical modeling, and ring shear tests to investigate the effects of rainfall on landslides in shallow-dipping red beds, using the Qingning landslide in SW China as an example. Our results suggest that the probable mechanisms leading to failure are (1) permeation of rainfall through the cracks at the back of the landslide site that increases the hydrostatic water pressure, which adds to the sliding stress and reduces the effective stress on the failure surface, gradually destabilizing the mass. In the Qingning landslide, the maximum water pressure was as high as 21.8 m before failure. When the factor of safety decreased markedly to 1.015, the sliding mass started to slowly slide. (2) As sliding takes place, the sliding zone soil is under undrained shear and its shear strength decreases sharply to a critical value, which promotes rapid sliding. In the Qingning landslide, the shear resistance of the sliding zone soil decreased markedly to 25.9 kPa as the pore water pressure increased to 118.3 kPa. This study may provide a theoretical basis for landslide forecasting in gently inclined red beds of the eastern Sichuan Basin as well as in similar geological settings worldwide.