Deterioration Effect of Sandstone Tensile Strength and Its Mesoscopic Mechanism under Dry-wet Cycles

The rock mass in the hydro-fluctuating zone of the reservoir bank slope is under dry-wet cycles for a long time, which will cause the deterioration of rock mass and induce geological disasters. In this study, a series of dry-wet cycle tests on the argillaceous quartz sandstone in the Three Gorges Reservoir area was carried out. Then, after different dry-wet cycles, the sandstone specimens were used to conduct the Brazilian splitting, scanning electron microscope, and 3D laser scanning tests. Herein, we provided detailed physical and microscopy image data to analyze the deterioration effect of tensile strength and mesostructure deterioration process of sandstone. With the increase of dry-wet cycles, the tensile strength of sandstone initially decreases rapidly, and then the decline rate tends to slow down. The evolution laws of fractal dimension and porosity are also significantly consistent with the deterioration of tensile strength. Moreover, further mesostructural analysis has revealed the repeated “absorption and swelling-dehydration and contraction” of clay minerals. This results in the breakage of framework mineral quartz and the expansion and connectivity of internal cracks, which ultimately deteriorates sandstone’s tensile strength.