Assessments of Tensile Characteristics and Degradation Mechanism of Sandstone Subjected to Wetting–Drying Cyclic Treatment

The properties of the rock masses are often degraded due to the rainfall, water storage and release, and other wetting–drying (W–D) cyclic effects, which would trigger a series of engineering geological disasters, e.g., landslides of reservoir slopes. However, the tensile behavior and degradation mechanism of rock subjected to W–D cyclic treatment have not been well understood. In this study, mesostructure observation, mineral analysis and static and dynamic tension experiments were performed to reveal tensile properties and deterioration mechanism of sandstone with different cycles of W–D treatment. Testing results showed that the tensile strength and dissipated energy of sandstone increase as the loading rate increases or cycles of W–D treatment decrease. The degree of rock fragmentation is enhanced by either increasing number of W–D treatment or loading rate. The fracture mode of sandstone under dynamic loading gradually transforms from transgranular fracture to intergranular fracture with increasing cycles of W–D treatment. The degradation mechanism of W–D cyclic sandstone is mainly attributed to the weakening of cementation, the shedding of grains and the enlargement of pores on the mesostructure. In addition, the mechanical deterioration of rock after W–D cyclic treatment is more significant than that in long-term immersion. The findings could facilitate a better understanding of the W–D cyclic effect on the rock properties and be helpful for the stability evaluation and disaster prevention of rock engineering in the W–D state.