The toppling failure of plate rock masses can be divided into different stages, and the geological history is long. The toppling failure concerning can be divided into two types: strong toppling and weak toppling. The classification of toppling failure is according to the angle of the toppling rock layer and the normal rock layer and the physical chrematistics of the failure surface. Table 1 shows the classification of the toppling failure of plate rock masses.Table 1Classification of the toppling failure of plate rock masses. As shown in Table 1, strong toppling is when the angle of the toppling rock layer and the normal rock layer is greater than 60��, while weak toppling is when the angle of the toppling rock layer and the normal rock layer is less than 60��.

The strong toppling always occurs in the upper slope at the upper part of the plate rock masses, and the weak toppling is below the strong toppling. The strong toppling occurs at a horizontal depth of approximately 50m, but the strong toppling is at approximately 100m. A toppling failure example in the Baqian slope illustrates the physical characteristics of strong toppling and weak topping. The dip of the Baqian slope is approximately 20��C40��. The toppling failure occurs in the plate sandstone, limestone, and mudstone. The normal rock layer is oriented in the dip direction of 325��C335�� and the dip of 75��C90��. The dip of the weak topping rock layer is 40��C50��, and the strong toppling is 20��C35��. The horizontal depth of strong toppling is approximately 29.1m�C72.5m, and weak toppling is approximately 90.7m�C111.

2m. The fracture and bending of the rock block and the dislocation of the rock layers result in the toppling of plate rock masses.3.4. Geological Process of the SlopeBased on the above geological analysis of rock-soil aggregate and toppling failure, the key characteristic of rock-soil aggregate is that it is layered, and for the toppling failure of plate rock masses, there are several fracture surfaces. Figure 8 shows the geological evolution process of slopes in the Gushui Hydropower Station Cilengitide region.Figure 8Geological evolution process of slope in the Gushui Hydropower Station region: (a) ancient landscape and (b) current landscape.