Sodium Sulfate Attack–Induced Deterioration of the Mechanical Characteristics and Its Deterioration Mechanism of Sandstone with Mode-I Crack under Dry–Wet Cycles

With the actual environments of the joint rock in the bank slope of the Three Gorge Reservoir region (in China) as the background and considering the research concept that the effect of sodium sulfates and the dry–wet (D–W) cycle on rocks as interactive and inseparable, a test plan for D–W cycles was designed to study the D–W cycle damage of the mechanical characteristics and their correlations with the strength properties of sandstone with a Mode-I crack exposed to a sodium sulfate attack. Based on the crack’s propagation radius and a damage variable reflecting a change in porosity, the degree of D–W cycle mechanical degradation was quantitatively analyzed. The mechanical characteristic of sandstone exhibited obvious damage under sodium sulfate attack and D–W cycles, among which the degree of D–W cycle degradation of the K_IC was the greatest, whereas the internal friction angle was relatively the lowest. Meanwhile, apparent consistency was observed between the K_IC and compression, and between the K_IC and tensile strength of specimen exposed to the sodium sulfates attack under D–W cycles. Moreover, an evident corresponding relationship existed among the deterioration damage of the mechanical properties, corresponding ion concentrations dissolved in sodium sulfate solution, and deterioration degree of the physical characteristics of sandstone. Meanwhile, the correlation relationships among physical and mechanical properties, D–W cycle damage degree, and ion concentration were obtained.