滑坡动力失稳定量分析

Quantitative Analysis of Dynamic Instability of Landslide

采用FLAC3D软件进行滑坡动力时程数值分析,对滑带单元的瞬时应力进行分解,得到滑带单元上垂直滑带的正应力和平行滑动方向的剪应力,据此定义滑带点安全系数以及滑坡整体安全系数。通过滑带点安全系数的动态空间分布特征以及滑坡整体安全系数的动力时程演化特征,定量分析滑坡的动力失稳。青海玉树结古镇至巴塘机场公路2#滑坡实例分析结果表明:地震作用下滑坡的动力失稳机理为推动式,与自重作用时一致;但地震作用明显降低滑坡的稳定性,且以滑坡中前部最为明显,最大降幅约30%;计算结果与滑坡的宏观变形特征相吻合,滑体中前部西杭引水渠附近震后出现密集的裂缝带,正是由于地震作用导致该部位滑带稳定性快速衰减所致。

The dynamic time history of landslide was analyzed by the FLAC 3D software, and the instantaneous stress of sliding zone unit was decomposed to obtain the normal stress perpendicular to the sliding zone and the shear stress parallel to the sliding direction. According to this, the point safety factor of sliding zone and the whole safety factor of landslide were defined. Based on the change in the dynamic spatial distribution of point safety factor and the change in the dynamic time history of whole safety factor in the test, the dynamic instability of landslide was quantitatively analyzed. The analysis results of the 2# landslide of Jiegu Town to Batang Airport Highway in Qinghai Province showed that the dynamic instability mechanism of landslide was the type of pushing, which was consistent with dead-weight effect. However, the stability of the landslide was obviously decreased by earthquake, especially in the middle front part of landslide, with a maximum decrease of about 30%. The calculation result was consistent with the macroscopic deformation characteristics of landslide. After the earthquake, the dense fracture zone appeared in the vicinity of the Xihang diversion channel located in the middle front part of the sliding mass. It was precisely due to the earthquake action that the stability of the sliding zone in this area decayed rapidly.