Abstract: After the impoundment and operation of reservoirs, the water level changes slowly or rapidly between the flood control water level of 145 m and the impoundment water level of 175 m every year. Rock and earth mass in the hydro-fluctuation belt is under cycle of drying-wetting conditions for a long time. The degradation of mechanical properties direct impacts on deformation stability of the bank slope. In this study, the experiments of testing under drying-wetting conditions are designed and conducted on the soils from the typical hydro-fluctuation belt. The results indicate that: 1) Shear strength of soil degrades under drying-wetting conditions. Specifically, shear strength deteriorates 75% by the first 4 cycles of the drying-wetting, and gradually becomes stable afterwards. 2) During the drying-wetting cycle, the internal microscopic cracks of the soil samples open and close repetitively, and then gradually grow and assemble; dense soil samples gradually loosen with increasing internal cracks. 3) Considering the degradation of soil properties during the drying-wetting cycles in hydro-fluctuation belt, the local safety factor of slope will degrade accordingly. The local slide and the developed cracks can be easily observed near the hydro-fluctuation belt in field investigation. The findings in this article can provide good reference for long-term deformation and stability evaluation on slopes in hydro-fluctuation belt.

Key words: bank slope, hydro-fluctuation belt, drying-wetting cycle, degradation, damage