Abstract: The variable amplitude of the reservoir water level is the stability sensitive area of the reservoir bank slopes. How will the rock mass strength degrade under the “saturation-air dry” circulation function and the geological hazards caused by the circulation function are very serious and inevitable problems. Thereafter, taking sand rock in the variable amplitude of typical reservoir bank in Three Gorges reservoir area, tests are performed to simulate the process of the “saturation-air dry” cycles. The experimental results show that the compressive strength, cohesion and internal friction angle of the sand rock samples all deteriorate gradually in the "saturation-air dry" cyclic process; and the change rules are basically consistent. Moreover, tests also show that the greater change of the water pressure in immersion, the longer of the soaking time and the more cycle numbers of the “saturation-air dry”, the more serious damage of the rock mass, which indicates that the rise or decline of water pressure and the "saturation-air dry" circulation function have cumulative damage on the samples. At last, water-rock interaction mechanism under the “saturation-air dry” circulation function are discussed in detail based on the experimental research. Research results have an important reference for the study of deterioration law of variable amplitude rock in reservoir bank, and provide favorable evidences for the long-term stability analysis of reservoir bank slopes.

Key words: saturation-air dry, circulation function, strength deterioration