降雨诱发滑坡阶跃型变形的预测分析及应用

滑坡进入蠕动变形阶段之后，往往难以及时开展勘察治理工作，合理的临灾预警是有效减少滑坡灾害损失的重要手段。首先确定降雨诱发“阶跃型”滑坡的预警关键判据为前期降雨、当次降雨、位移速率，并引入“一个降雨过程”定义滑坡监测的降雨区间，将预警过程分为当次降雨和前期降雨+当次降雨两种模式。然后运用最小二乘法确定滑坡“阶跃”变形曲线上的“破坏拐点”和“稳定拐点”用以确定变形加速区间，以此求解前期降雨、当次降雨以及移速率阈值。最后以王家坡滑坡为例，设计了两种模式下的5级递进式分级预警模型。研究表明：（1）前期降雨与当次降雨组成“一个降雨过程”的时间间隔为7 d；（2）王家坡滑坡的位移速率阈值为20 mm/d；（3）前期降雨+当次降雨模式下王家坡滑坡的前期降雨、当次降雨阈值分别为10、15 mm，当次降雨模式下王家坡滑坡的降雨阈值为25 mm。

Forecast analysis and application of stepwise deformation of landslide induced by rainfall

After the landslide enters the creep deformation stage, it is usually difficult to carry out the investigation and management of the landslide in a timely manner. A reasonable early warning system becomes an important means for effectively reducing landslide hazards. This paper first determined that the key early warning criteria for stepwise landslide induced by rainfall: previous rainfall, current rainfall, and displacement rate. Moreover, one rainfall process is introduced to define the rainfall interval for landslide monitoring, and the warning process is divided into two modes of the previous-current rainfall and the current rainfall. Then the least squares method is used to define the failure inflection point and the stability inflection point on the displacement deformation curve of the stepwise landslide. Thus, the deformation acceleration interval of the landslide is determined to solve the previous rainfall, the current rainfall and the displacement rate threshold. Finally, taking the Wangjiapo landslide as an example, this paper designs the five-level progressive early warning system under two modes. The results show that: (1) the time interval of a rainfall process constituted by the previous rainfall and the current rainfall is 7 days; (2) the displacement rate threshold of Wangjiapo landslide is 20 mm/d; (3) in the mode of the previous-current rainfall, the previous rainfall threshold and the current rainfall threshold of the Wangjiapo landslide are 10 mm and 15 mm, respectively, and the rainfall threshold of the Wangjiapo landslide under the current rainfall mode is 25 mm.