Abstract: Under the condition of long-term cyclic saturation-air drying, long-term stability of reservoir bank slopes are affected by their dynamic characteristics change rules, and the hydro-fluctuation belt is the sensitive area. Thereafter, taking typical sandstone in the hydro-fluctuation belt of reservoir bank in Three Gorges reservoir area, a test scheme is designed with the consideration of coupling interaction of water pressure changes and saturation-air dry cyclic function, and uniaxial cyclic loading and unloading dynamic response tests of sandstone with different saturation-air dry cycle periods are carried out. The experimental results show that the hysteresis loop area of dynamic stress-strain curve and axial strain of the sandstone samples increase gradually when they experience the same times cyclic loading and unloading, and the dynamic elastic modulus of sandstone samples decrease gradually and damping coefficient, damping ratio increases gradually during the saturation-air dry cyclic process, which indicates that the saturation-air dry cyclic function has a cumulative damage of dynamic characteristics on the samples. Finally, degradation mechanisms of dynamic characteristics under the saturation-air dry cyclic function are discussed in detail based on the microscopic structure change of sandstones. Research results have an important reference for the long-term stability analysis of reservoir bank slopes considering the earthquake action.

Key words: cyclic saturation-air drying, cyclic loading and unloading, damping ratio, damping coefficient, dynamic elastic modulus