北川县白什乡老街后山滑坡监测及失稳机制分析

北川县白什乡老街后山滑坡位于四川省绵阳市北川县城以西, 该滑坡发现时已处于变形发展较快的状态, 前缘多处崩塌, 坡面张拉裂缝密布。为了准确地判断滑坡的稳定性现状, 预测预报滑坡的下滑时间指导避险, 对滑坡开展了专业监测, 专业监测工作持续到了滑坡失稳下滑。本文对滑坡从监测到下滑的变形演化阶段进行了划分, 对各变形阶段滑坡的监测成果及变形破坏特征进行了分析研究。随后在此基础上分析滑坡形成演变过程及失稳机制, 通过分析认为白什乡滑坡形成演变模式为弯曲-拉裂(倾倒)变形模式, 滑坡形成后失稳机制为推移式和牵引式复合型。根据监测成果及宏观变形迹象对滑坡进行了分区, 判断出滑坡失稳下滑的关键控制部位是滑坡前缘Ⅰ-3区, 因此Ⅰ-3区监测数据是准确预测预报滑坡下滑时间的关键数据。

DEFORMATION MONITORING AND FAILURE MECHANISM ANALYSISOF BAISHI LANDSLIDE IN BEICHUAN COUNTY

The Baishi landslide is located at the west of Beichuan county, Mianyang, Sichuan Province. The landslide was detected due to fast deformation that caused several small collapses and falls in the front of the unstable slope as well as densely distributed tensile cracks in the slope. In order to better understand the stability status and estimate the failure time of the unstable slope, a comprehensive monitoring system was carried out after the deformation was reported. The monitoring was continued till the slope failed. This study analyzes the landslide deformation phases and failure mechanism using the monitoring data. The result shows that the failure mode of the Baishi landslide is bending-tensile(toppling).The failure has both the retrogressive and advancing features. The landslide is divided into several zones according to the spatial variation of deformation characteristics over the slope. The monitoring results indicate that the front part of the slope(Zone I-3)plays a key role in controlling landslide stability. Therefore, the monitoring data of this zone is significantly important for predicting the failure time of the whole landslide.