An analysis on the destruction mode of Wuxia scissors peak down the shore slope in the Three-Gorges Reservoir area

Abstract

Scissors peak bank slope is located in the left bank of Wushan gorge in the Three Gorges Reservoir area, with a total length of 2.1 km. Influenced by Shennv peak box anticline in the north and Shennv Xi-Guandukou syncline in the south, the bank slope is steeply sloping bedding rock bank slope. The slope of the bank is 45°～89°, and the whole is a composite landform of steep slope and steep cliff.The quaternary strata exposed on the bank slope are mainly cluvial gravel soil, and the exposed bedrock contains the strata of the 3rd and 4th members of the Triassic daye formation and the 1st to 4th members of the Jialingjiang formation. The strata are diversified.The rock groups are mainly hard rock group composed of carbonate lute of Daye formation and Jialingjiang formation and soft rock group composed of karst breccia of the second member of Jialingjiang formation. The rock mass structure ranges from very thin layer to very thick layer, and the slope topography, stratum, rock group and structure are complex. Within a range of 2.1 km from upstream to downstream of the bank slope, the slope structure changes greatly, the deformation and failure characteristics of the bank slope vary greatly, and the formation mechanism and failure modes differ greatly. According to the different geological conditions and characteristics of the slope, it can be divided into 6 large sections and 6 sub-sections.Based on the characteristics of the macroscopic deformation and failure of the bank slope, the current deformation and failure of the bank slope are summarized into four aspects: "structural cutting and unloading", "local fracturing, sliding", "surface dissolution", and "rock mass deterioration in the subsidence zone", and the failure modes of each section are analyzed from the perspective of the formation mechanism of the bank slope. In addition, this study also analyzed the deterioration characteristics of rock mass in the bank slope above the reservoir water level and the reservoir water level fluctuation area, and proposed four types of rock mass deterioration and failure types from the perspective of rock mass deterioration: progressive release slip along the plane, collapse slip along the weak interlayer, X-type joint slip, and toppling collapse along the plane.

Keywords

• steeply dipping bedding rocky bank slope
• genetic mechanism
• failure mode
• rock mass degradation
• the three-gorges reservoir area