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. The static and dynamic tensile strength of sandstone gradually decreases with increasing cycles of wetting-drying treatment.The effect of loading rate and wetting-drying cyclic treatment on energy dissipation of sandstone is related to mesoscopic fracture modes.The physical changes in sandstone mesostructure after wetting-drying cyclic treatment lead to the deterioration of its macroscopic properties.

Automated summary

This study investigates the tensile properties and degradation mechanism of sandstone subjected to wetting-drying (W-D) cyclic treatment through mesostructure observation, mineral analysis, and static and dynamic tensile experiments. The results show that the tensile strength and dissipated energy of sandstone increase with increasing loading rate and decreasing cycles of W-D treatment. The degree of rock fragmentation is enhanced by increasing number of W-D treatment and loading rate. The fracture mode of sandstone changes from transgranular fracture to intergranular fracture with increasing cycles of W-D treatment.