降雨条件下大型滑坡体渗流稳定性分析

西南高山峡谷地区，大型滑坡体分布广泛，降雨作用下极易产生失稳。古水水电站争岗特大型滑坡堆积体方量高达4 750×104 m3，存在多处厚度超过50 m 的超深层滑坡。2008年强降雨导致滑体变形再次启动并加剧，依据野外勘测，首先对地质结构和水文条件进行了分析，基于此对降雨入渗机制和稳定性现状开展了定性评价，认为降雨引起了滑体材料强度降低，整体处于沿贯通底滑面蠕滑变形的状态，须开挖加固治理。其次，运用饱和非饱和渗流理论，对降雨条件下滑体开挖治理前、后渗流特性进行了定量研究，揭示了入渗引起滑动变形的动态机制，并对稳定性和治理措施进行了评价，提出了有效的排水措施。结果显示，入渗引起土体饱和，形成浸润线并出现滞水现象；治理前滑体局部和滑带处滞水严重，雨停4 d后，滞水层厚度最高达6 m，此时稳定性最差；治理后滞水层明显减小，稳定性显著提升。其结果真实地反映了滑体稳定性现状与规律，与现场勘查相吻合。治理措施亦有显著效果，依据滞水层分布位置，提出相关排水措施，更有利于保持其稳定性。研究成果可为类似工程问题提供有意义的参考。

Analysis of seepage stability of large-scale landslide under rainfall condition

The large-scale landslides, widely distributed in southwest mountains and canyons, are prone to produce instability due to rainfall. In Gushui hydropower station，not only is the extremely large volume of Zhenggang large landslide accumulation body up to more than 4 750×104 m3, but also the thicknesses of many ultra-deep landslide are over 50 m. Under the influences of the heavy rainfall in 2008, the landslide started to deform again and even more seriously. According to the results of field engineering geological investigation and analysis of geologic structure characteristics and hydrogeology conditions, the mechanism of rainfall infiltration and stability in the current situation was qualitatively analyzed first. Then the whole landslide was transfixed slipping surface in the state of creep deformation; so it should be treated such as excavating and reinforcing. Combined with the analysis result, quantitative study of the seepage properties of landslide showed the dynamic sliding mechanism that water infiltration caused deformation, evaluated the stability and treatment, thus proposed effective drainage measures before and after the treatment under the rainfall. The results also showed that the saturation line and backwater was formed due to saturated soil by infiltration. Before the treatment, the backwater was seriously persisted in local landslide and slip surface; and the worst stability came out 4 days later after the rain stopped; and the maximum thickness of backwater increased up to 6 m. However, with backwater reduced obviously, the stability was significantly increased by the treatment. The results truly reflected the situations and laws of the stability of landslide, which were consistent with the results of field exploration. The results were significantly improved by the treatment. Drainage measures proposed would keep the landslide’s stability efficiently. The research results will be useful and meaningful in the same projects as reference.