Abstract: The slope along the north bank of a major bridge in the Southwest Three Gorges Reservoir Area is a high and steep rock slope consisting of interbedded sandstone and mudstone. The stability of this slope is critical to the construction of the bridge. Geological mapping, drilling and digital borehole panoramic image are used to identify the geological characteristics of the daylighting slope. Based on the engineering geology and the stereographic projection analysis, the stability of the slope was preliminary assessed. Subsequently, the potential for the sliding along the bedding plane of the slope was analyzed by using the limit equilibrium method. The finite difference method (FLAC) and the discrete element computation program (UDEC) were then employed to simulate the failure mode, mechanical behavior, and strength of the rock mass, considering only the structural plane conditions of the slope. The results indicate that the daylighting slope is stable under both natural conditions and bridge foundation load conditions. There is no risk of sliding failure along the daylighting bedding plane. However, under the long-term effect of the natural gravity, local rock masses on the slope surface may suffer damage, resulting in retrogression of the bank slope, which could potentially affect the safety of the bridge foundation. It is recommended to appropriately fill in the grooves on the rock slope surface of the north bank and take corresponding treatment measures such as clearing and supporting the overhanging rock blocks.

Key words: Southwest Three Gorges Reservoir Area, High and Steep Interbedded Mudstone &, Sandstone Rock Slope, Sliding along Daylight Bedding Plane, Slope Stability