Reactivation and deformation mechanism of ancient landslides by excavation

The Dalixi ancient landslide in Xingshan County in the Three Gorges Reservoir area is taken as an example. Based on the analysis of its characteristics, the deformation characteristics and temporal-spatial laws of surface cracks of the ancient landside in the process of landslide revival are analyzed by use of geological survey, site inspection for nearly one year, artificial GPS displacement monitoring data and automatic monitoring data. Based on the Geo-Studio simulation, the influences of excavation and rainfall on the revival deformation of the ancient landslide and the primary and secondary relationships are determined. The results show that: (1) The Dalixi landslide is a middle-steep consequent ancient rock landslide with soft layer in geological history period. (2) The deformation of Dalixi landslide is closely related to excavation. In the early stage, it concentrates near the leading edge Q3 of the first excavation area, and gradually appears along the excavation direction at the leading edge Q4 and Q5, and finally evolves into the secondary landslides near the leading edge Q5. At the same time, the vertical deformation gradually advances to the middle and rear, showing the characteristics of progressive retrogression. (3) The excavation is the inducing factor for the revival of landslide deformation, and the rainfall is the stimulating factor. Both of them work together to promote the sustainable development of landslide deformation