To reveal the impact of slope angle change on toppling deformation, this paper takes the dam toppling deformation of Gushui Hydropower Station based at Lancang River as an example, based on which three groups of models with different slope angles are conceptualized and designed. Through the centrifuge test, the evolution of toppling deformation of a counter-tilt layered slope under different slope angles was simulated. The research results show that: (1) The steeper the slope angle, the shorter the cumulative time required for such deformation is, the larger the toppling deformation will be, and it is more likely that multi-stage fracture zones will occur during the toppling process. (2) The toppling deformation process can be summarized as four stages. (3) The toppling deformation mainly occurs above the datum surface of the toppling fracture; the angle between the datum surface and the normal of the layer is between 12° to 16°. This value shall not change as the slope angle changes. (4) The lesser the slope angle is, the more likely the toppling deformed slope will be experience overall slipping instability. while the steeper the slope angle is, the greater the possibility of collapse after the rock mass falls.

The deterioration mechanism of red-bed soft rock is attributed to microstructural changes induced by water–rock interactions, where the damage to pores and the development of fractures significantly impact its macroscopic mechanical performance. The microstructural deterioration pattern of red-bed rock with different water saturation times was obtained by scanning electron microscopy (SEM), which showed that the microdamage effect of mudstone is an evolutionary process comprising the dissolution and detachment of its internal soluble bond structure. Three-dimensional (3D) images of the water-saturated damage of the rock mass were extracted by computed tomography (CT) scanning and calculated based on the box-counting algorithm to obtain the fractal dimension of the fracture development, leading to the theory that a soft rock fracture has multiple fractal characteristics. With the continuous increase in the water saturation time, the pores inside the rock mass began to reorganize and connect, and the mudstone specimens showed accelerated damage and some self-similarity. Furthermore, chemical element testing was conducted on the solutions used for water saturation, leading to the establishment of a microscopic interfacial evolution model describing water–rock damage, with theoretical equations derived based on diffusion theory.