Abstract
In the 12 years since the impoundment of Xiangjiaba Reservoir, 28 bank slopes have deformed and necessitated remediation due to reservoir impoundment. This study conducted a statistical analysis of the distribution and types of the 28 deformed bank slopes, revealing that significant proportion of the deformed slopes are red-bed deposits with straight-line deposit-bedrock interfaces. To reveal the deformation mechanism of bank slopes with straight line deposit-bedrock interfaces, two red-bed deposits (D4 deposit and D8 deposit) with significantly different deformation characteristics were selected as study objects. Engineering geological investigations found differences in both the dip angle of the deposit-bedrock interface and the deposit materials between the two deposits. Surface displacement monitoring showed that the displacement curve of D4 deposit exhibited a step-like pattern, while that of D8 deposit exhibited a continuous growth pattern. The numerical simulation results showed that when a high water level is maintained, gentler deposit-bedrock interface dip angles are more likely to result in a safety factor falling below the initial value; when the water level drops, lower permeability coefficients lead to greater decreases in the safety factor. The comprehensive analysis suggested that the core difference in deformation between the two deposits lies in the dip angle of the deposit-bedrock interface. A steeper deposit-bedrock interface leads to deformation primarily controlled by seepage forces during the water level drop, while a gentler interface induces continuous deformation due to the synergistic action of buoyant force and seepage force. The research findings can provide theoretical and technical support for reservoir bank disaster prevention and control, as well as engineering remediation in the Jinsha River basin and similar red-bed reservoir areas.