Deterioration laws of weak interlayers on slopes during wetting-drying cycles

Abstract

Weak interlayers in reservoir slopes can significantly impact the construction and operation of hydropower projects. Considering the existence of multiple weak interlayers facing outward on the slope within the left bank slope of Caiziba pumped storage plant located in Fengjie, Chongqing, there is an urgent need to identify the effects of high-frequency, rapid, and cyclic water level changes on its stability. The study involved creating a geological model and using 3D laser scanning and 3D printing technology to prepare several groups of weak interlayers with varying roughness. Shear tests were conducted under natural and fully wet conditions to investigate the strength deterioration of weak interlayers with different roughness after multiple wetting-drying cycles. The results were verified through numerical simulation. The results indicate that the shear strength increases with the roughness of the weak interlayer under the same number of cycles. Additionally, the residual curve stepwise decreases with an increase in the number of cycles. When the roughness remains constant but the number of cycles is different, an exponential decrease in the shear strength of the interlayer occurs with an increase in the number of cycles. The impact of the number of wetting-drying cycles on the strength gradually weakens. After six cycles, the shear strength decreases by 90% and stabilizes at a value that is positively correlated with the roughness. Multiple wetting-drying cycles significantly impact the strength of the weak interlayer and the slope stability in the reservoir area. This study summarizes the deterioration law, which can serve as an important reference for analyzing the slope stability in similar projects.