Abstract: Due to reasons such as the reservoir water level fluctuation and rainfall preliminarily, alternate wetting and drying usually occurred in the rock, which is fairly harmful for long term safety of rock. Taking argillaceous sandstone in Three Gorges Reservoir area as the research object, the conventional uniaxial and triaxial compression tests after the action of wet and dry cycle in acid environment, have been conducted to obtain the relevant mechanical parameters of the argillaceous sandstone in wet and dry cycle of acid environment. Relative to the dry specimen without dry-wet cycle, there are different degrees of reduction in elastic modulus , uniaxial compressive strength ,cohesion and internal friction angle of argillaceous sandstone with different times of dry-wet cycle. Overall trends of substantial decrease of various mechanical in dices appears, at which saturated with water for the first time, then the decrease of amplitude reduces with the increase in wet and dry cycles. Meanwhile, the pH value of acid environment has a great influence on the mechanical properties; there is a critical pH value influencing the mechanical properties of argillaceous sandstone. The influence of acid environment on mechanical properties of argillaceous sandstone significantly increase in the case below this critical value, there is smaller influence on its mechanical properties when the pH value is higher than the critical pH value.

Key words: argillaceous sandstone, pH value, dry-wet cycle, strength