DEVELOPMENTAL CHARACTERISTICS AND FORMATION MECHANISM OF THE RIZHA POTENTIAL GIANT ROCK LANDSLIDE, WESTERN SICHUAN PROVINCE, CHINA

The Rizha potential giant rock landslide is located on the left bank of Jiangqu River, Sichuan Province, with many alpine canyons and large vertical river slopes. The eastern boundary fault of Jinsha River fault zone, which has been active since late Pleistocene, passes through the foot of the slope. Based on remote sensing interpretation, field investigation and geophysical test analysis, the development characteristics and formation mechanism of the Rizha giant rock landslide are analyzed in this paper. It is considered that the Rizha landslide is a large deep giant potential rock landslide, which was formed under the influence of fault activity, karst water, long-term unloading and gravity. The Rizha landslide could be divided into three sub-zones spatially, i.e., the rear tensile deformation zone(Ⅰ), middle compression deformation zone(Ⅱ) and slope foot stress concentration zone(Ⅲ). The Rizha potential giant landslide is currently dominated by creeping deformation. There are four large tensile cracks developed well at its rear edge, with the maximum crack width up to 20~35 m and the depth up to 190 m by the geophysical data interpretation. The study result revealed that there were two main instability types of the Rizha giant potential landslide, the first one is the high shear instability type, with potential instability volumes of 7.9~10.2×10⁷ m³(H₁), 2.3~2.9×10⁸ m³(H₂), 4.8~7.2×10⁸ m³(H₃) and 6~10×10⁸ m³(H₄), and the other is deep-buried creeping deformation type, with deep-buried creep sliding zone and locking section in the deepen part of the sliding body. The maximum deformation thickness of the creeping body is 300 m(H₅). The locking section of the Rizha landslide is likely to fail under the long-term unloading and gravity, earthquake activity, karst water activity, and the geo-hazard chain of the high-level rock falling-sliding-blocking the river is likely to occur. The deep creeping sliding might have great influence on the stability of major projects built in the slope, such as deep-buried tunnels. This kind of potential giant rock landslides are typically developed on the Tibetan Plateau. It is recommended to make further investigation of the Rizha potential giant landslide, to find out the spatial structural characteristics and stability, as well as monitoring and early warning if necessary.