长江三峡库区谭家湾滑坡基本变形特征及机理分析

三峡库区谭家湾滑坡自2006年实施专业监测以来,一直持续变形,尤其是自2015年以来,变形趋势逐年增大,对库区村民的生命、财产安全造成巨大威胁。根据长期的野外地质调查、宏观巡查、滑坡地表裂缝位移自动监测数据以及12余年的人工GPS监测数据等,分析了该滑坡在强降雨和库水位变化条件下的基本变形特征和变形机理。结果表明:谭家湾滑坡属于中厚层圈椅状的降雨型牵引式土质滑坡,强降雨和持续性降雨是影响滑坡变形的主要外因,库水位变动对谭家湾滑坡影响较小。谭家湾滑坡在持续性降雨和强降雨条件下会产生明显响应,当日降雨量>90 mm或前3 d累计降雨量达到50 mm,并且当日和前1 d降雨量均>15 mm,地表裂缝位移-时间曲线、累计位移-时间曲线会出现明显的阶跃现象。目前,谭家湾滑坡变形趋势逐年增大,边界裂缝基本形成,在强降雨等极端条件下产生滑动的可能性很大,必须进一步加强监测。

Basic Deformation Characteristics and Mechanism of Tanjiawan Landslide in the Three Gorges Reservoir Area

Since the implementation of professional monitoring in 2006, the Tanjiawan landslide in the Three Gorges reservoir area has seen a continuously increasing displacement. Especially since 2015, the deformation trend has intensified, posing a great threat to the lives and property safety of villagers in the reservoir area. According to long-term field geological survey, macroscopic inspection, automatic monitoring data of landslide surface crack displacement and artificial GPS monitoring data for over 12 years, we examined the basic deformation characteristics and deformation mechanism of the landslide under heavy rainfall and reservoir water level fluctuation. Results suggest that the Tanjiawan landslide is a rainfall-triggered retrogressive landslide with medium-thick layer chair-shaped groove shape. Heavy rainfall and continuous rainfall are major external factors affecting landslide deformation, while water level fluctuation has little effect. Heavy rainfall and continuous rainfall led to evident response: when daily rainfall exceeds 90 mm or the accumulated rainfall of previous three days reaches 50 mm while rainfall on the same day and the previous day exceeds 15 mm, the surface crack width-time curve and the cumulative displacement-time curve will witness an apparent step upward. At present, the deformation of Tanjiawan landslide is increasing year by year, with boundary cracks basically formed. It is highly probable that sliding will occur under extreme conditions such as heavy rainfall. Automatic monitoring equipment and detail inspection must be strengthened.