金沙江白格滑坡残留体失稳堵江风险分析

2018年10月10日和11月3日，金沙江上游白格滑坡两次滑动形成堰塞湖，对下游造成了巨大破坏。目前其滑源区边界外仍存在K1、K2和K3等3处规模较大的残留体，有再次失稳堵江的可能性，对下游4座在建水电站构成威胁。受滑坡区自然地理地质条件制约，对白格滑坡残留体的规模、可能的失稳模式、一次失稳体积等方面的研究工作较少，不能为金沙江上游相关建设风险管理提供支撑。针对上述问题，2019年对滑坡残留体开展了精细地形测量、变形现象详细调查、深部结构探测等工作，系统分析了三处残留体的体积、失稳方式、可能的失稳组合；在考虑失稳体的铲刮效应、运动轨迹、松方系数等基础上对残留体入江规模进行了分析；根据河谷地形数据，基于PFC3D软件模拟和“10·10”、“11·3”两次白格堰塞体的形态特征，对不同失稳规模进行了堰塞体堆积形态预测。结果表明，三处残留变形体体积分别为159.3×104m3、460×104m3、142×104m3；滑坡残留体存在小规模坍塌、大范围卸荷变形、一定规模岩土滑移失稳三种变形破坏形式；最危险失稳工况以1-4、2-1、3-1、3-2四个亚区同时失稳可能性最大，失稳总体积达271×104m3；白格滑坡残留体不同失稳工况下，沿主滑槽入江堆积最大堆积高度47.5m，堆积高程2937.5m。沿白格滑坡凹槽上游斜坡入江堆积最大堆积高度28.7m，堆积高程2923.7m。

River Blocking Risk Analysis for the Residual Unstable Masses of the Baige Landslide at the Jinsha River

On October 10 and November 3, 2018, the Baige landslide blocked the Jinsha River twice, causing huge damage to the downstream. there are still three large-scale residual deformation bodies K1, K2, and K3 around the previous sliding source area, which may be slide again and block the river. Restricted by the natural geological conditions of the landslide area, there is little research work on the residual Baige landslide, which cannot provide support for the risk management of the Jinsha River hydropower project construction. Based on the topographic survey, deformation measurement, and deep structure detection in the deformation area, the volume, destabilization mode, and possible sliding combinations of the three residual bodies were analyzed. The scale of the unstable body entering the river was evaluated on the basis of scraping effect, motion trajectory, loose factor, etc.. Based on the current valley topographic data, the previous barrier body morphology analysis and PFC3D software simulation, the future barrier body parameters were predicted for different sliding modes. It shows, the volume of three unstable areas reaches separately 159.3×104m3, 460×104m3, and 142×104m3; there are three types of destabilization in the residual body of Baige landslide, namely, small-scale collapse, large-scale unloading deformation, and sliding; the possible and the most dangerous combination is that the four sub-zones 1-4, 2-1, 3-1, and 3-2 slide at the same time with the volume of 271×104m3; under different sliding conditions of the deformable rock, the maximum height of barrier body is 47.5m with the ground elevation 2937.5m when sliding along the main chute into the river, and 28.7m with the ground elevation 2923.7m when sliding along the upstream slope of the Baige landslide groove.