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2011年9月16日,南江县普降大暴雨,引发了大量沿基覆界面滑动的堆积层滑坡。为研究强降雨诱发沿基覆界面滑动的浅表层堆积层滑坡形成机制,利用自主研制的离心场降雨模拟设备,通过大型离心模型试验,再现了强降雨引起红层地区堆积层边坡滑动失稳的全过程,获得了边坡变形破裂的特征参量,阐明了边坡的滑动失稳机制。研究表明:(1)在0~50 g加载过程中,土压力和孔隙水压力随加速度的增加而逐渐增大,坡体的含水率缓慢降低,滑带土的含水率缓慢升高;(2)在第1次降雨过程中,SP1、SP2土压力计测值继续增大,SP3、SP4土压力计测值变化不大,说明滑体前缘及中部已承受来自滑体后部的推力。4个孔隙水压力计测值逐渐增大至最大,停雨后,4个孔隙水压力计测值均减小,说明在降雨过程中,孔隙水向基覆界面逐渐汇聚,雨停后,基覆界面的孔隙水逐渐消散。滑体中MC3含水率传感器测值逐渐变大,过20 s后,滑带中MC2含水率传感器测值也逐渐增大。(3)在第2次降雨90 s时,4个土压力计、4个孔隙水压力计测值变化大,两个含水率传感器测值迅速降低,说明此时边坡呈现整体滑动。之后,SP1、SP2和SP3土压力计测值缓慢增大到最大。SP4土压力计测值一直下降;4个孔隙水压力计测值缓慢增大至最大,第2次雨停后,4个土压力计、4个孔隙水压力计和2个含水率传感器测值逐渐减小。(4)最后,通过模型和原型的综合对比分析,该边坡的滑动失稳机制为推移式蠕滑-拉裂-整体滑动。
On September 16, 2011, the heavy rainfall in Nanjiang County caused a large number of landslides that slide along the foundation-base interface. In order to study the formation mechanism of superficial buildup landslide induced by heavy rainfall, the authors used centrifugal model rainfall simulator independently developed by large-scale centrifugal model test to reproduce the slip instability of the slope of the buildup layer in the red layer due to heavy rainfall The characteristic parameters of slope deformation and rupture are obtained, and the slip instability mechanism of the slope is clarified. The results show that: (1) During 0 ~ 50 g loading, the soil pressure and pore water pressure gradually increase with the increase of acceleration, the water content of slope body slowly decreases, and the water content of slip soil slowly increases; During the first rainfall, the measured values of earth pressure meter of SP1 and SP2 continued to increase, and the measured values of earth pressure meter of SP3 and SP4 did not change much, indicating that the front and middle of the sliding body had already received the thrust force from the rear of the sliding body. The measured values of 4 pore water pressure gradually increased to the maximum. After the rain stopped, the measured values of 4 pore water pressure decreased, indicating that during the rainfall, pore water gradually converged to the interface of the foundation and coating. After the rain stopped, The interface pore water gradually dissipated. The measured value of MC3 moisture content sensor in the sliding body gradually becomes larger. After 20 s, the measured value of MC2 moisture content sensor in the sliding zone also gradually increases. (3) At 90 s of the second rainfall, the measured values of the four earth pressure gauges and the four pore water pressure gauges changed greatly, and the measured values of the two moisture content sensors decreased rapidly, indicating that the slope showed the overall sliding at this time. After SP1, SP2, and SP3 earth pressure gauge slowly increased to the maximum. The measured value of SP4 earth pressure gauge has been decreasing. The measured values of 4 pore water pressure slowly increased to the maximum. After the 2nd rain stopped, 4 earth pressure gauges, 4 pore water pressure gauges and 2 water content sensors measured slowing shrieking. (4) Finally, through the comprehensive comparative analysis of the model and the prototype, the sliding instability mechanism of the slope is the creep-pull-slip-overall sliding.