降雨与开挖作用下黄土滑坡失稳过程分析:以关中地区长武县杨厂村老庙滑坡为例

Analysis of instability process of the loess landslides under rainfall and excavation actions:A case study of Laomiao landslide at Yangchang Village in Changwu County,Guanzhong area

降雨入渗和人工开挖是诱发黄土滑坡的重要因素,为了研究在这2种诱因作用下关中地区黄土滑坡失稳过程及其对稳定性的影响,以陕西省长武县杨厂村老庙滑坡为研究对象,通过现场调查、地质测绘和钻孔勘探,查明了该滑坡变形特征,定性分析了滑坡变形演变过程;基于滑坡变形前15 d内日降雨量实测值,采用有限元软件,对坡脚开挖后连续降雨作用下滑坡形成过程进行了仿真模拟;基于强度折减法对该滑坡稳定性变化规律进行了研究。结果表明:①关中地区特殊的地层结构是滑坡变形的内因,降雨是最主要的诱发因素;②滑坡失稳演化过程表现为:坡体处于蠕滑状态,坡脚开挖后,坡体前缘失稳,牵引中后缘坡体向下错动而产生张拉裂缝,在降雨作用下,雨水沿裂缝渗入坡体深部,滑坡中部岩土体浸水后抗剪强度降低,从而导致黄土层与红黏土层接触面饱水形成贯通滑带,诱发深层滑坡;③滑坡开挖后较初始状态,稳定性系数降幅为0.102,此后受连续降雨影响,稳定性系数在前10 d以平均0.010/d的速率缓慢下降,第10~13 d以0.034/d的速率快速下降至最低,第13 d以后开始回升。研究结果可以为该类滑坡防治提供有效依据。

Rainfall infiltration and artificial excavation are important factors inducing the loess landslides.To study the deformation process of loess landslides in the Guanzhong area and its influence on stability under the two inducements,the Laomiao landslide in Yangchang Village,Changwu County,Shaanxi Province is taken as the research object.Through field investigation,geological mapping and borehole exploration,the deformation characteristics of the landslide are determined,and the deformation evolution process of the landslide is qualitatively analyzed.Based on the measured daily rainfall within 15 days before the landslide deformation,the process of landslide formation under continuous rainfall after excavation actions at the slope foot was simulated by using finite element software.Based on the strength reduction method,the stability variation law of the landslide is studied.The results show that:①the special formation structure in the Guanzhong area is the internal cause of landslide deformation,and rainfall is the most important inducing factor;②the deformation evolution process of the landslide:at first the slope was in a state of creep.After the excavation actions,the anterior edge of the slope became unstable,and then the trailing edge of the slope was drawn downward,resulting in tension cracks.Under the influence of rainfall,rainfall infiltrated along the fissures of the slope,while the shear strength of the rock and soil mass in the central part was reduced,resulting in the sliding interface between the soil layer and red clay layer.Ultimately a deep landslide was induced.③After the landslide excavation,the stability coefficient decreased by 0.102,as compared with the initial state.Then,influenced by continuous rainfall,the stability coefficient decreased slowly at an average rate of 0.010/d in the first 10 d,and rapidly decreased to the lowest rate of 0.034/d in 10-13 d,and began to rise after 13 d.The research results are expected to provide effective basis for the prevention and control of such landslides.