静宁县田堡调蓄水池滑坡成因及稳定性分析

2020年9月18日，甘肃省平凉市静宁县四河镇田堡村田堡调蓄水池左岸发生滑坡，滑坡长180 m，宽240 m，体积48.5×104 m3，主滑方向191°，为黄土-泥岩老滑坡的复活。滑坡破坏已开挖的边坡和公路路基，严重威胁田堡调蓄水池的正常建设。通过现场勘查、岩土试验和计算等工作，对田堡调蓄水池滑坡形成的地质条件、滑坡基本特征及滑坡成因进行了探讨，并采用简化Janbu法对滑坡稳定性进行分析。研究发现，滑坡形成条件主要为老滑坡地质基础、坡体前缘开挖、持续性强降雨三个方面，即坡脚大规模开挖和强降水的共同作用下，引发老滑坡的复活滑动。稳定性计算结果表明，在坡脚开挖后坡体滑动前，暴雨条件下坡体稳定系数小于0.98，处于失稳滑动状态，滑动后各工况稳定系数小于1.05，处于不稳定—欠稳定状态。

Causes and stability analysis of the landslide at Tianbao Reservoir in Jingning County,Gansu Province

On September 18, 2020, a landslide occurred on the left bank of Tianbao Reservoir in Tianbao Village, Sihe Town, Jingning County, Pingliang City, Gansu Province. The landslide is 180 m long, 240 m wide, 48.5×104 m3 in volume, and 191° in main sliding direction, which is the revival of the old loess-mudstone landslide. Landslide destroys the excavated slope and highway subgrade, which seriously threatens the normal construction of Tianbao Reservoir. Through field investigation, geotechnical test and calculation, the geological conditions, basic characteristics and causes of landslide formation in Tianbao Reservoir were discussed, and the stability of landslide was analyzed by simplified Janbu method. The study found that the formation conditions of the landslide are mainly three aspects : the geological foundation of the old landslide, the excavation of the front edge of the slope, and the continuous heavy rainfall. That is, the old landslide is caused by the large-scale excavation of the slope toe and the heavy rainfall. The stability calculation results show that after excavating the slope toe, the stability coefficient is less than 0.98 under the rainstorm condition, which is in the unstable sliding state. After sliding, the stability coefficient of each working condition is less than 1.05, which is in the unstable-unstable state.