Extensive water–rock interaction in the Three Gorges Reservoir area of the Yangtze River leads to rock mass deterioration along the reservoir banks. However, mineral evolution behavior and its effect on the mesostructure deterioration of rocks under the wetting–drying cycle condition remain unknown. So, the wetting–drying cycle tests were conducted on peculiar argillaceous quartz sandstone in TGRA under neutral (pH = 7) and alkaline (pH = 10) water environments. Here, we provided detailed physical and microscopy images data to determine the control mechanism of mineral behavior on the evolution of sandstone’s mesostructure. Under the neutral condition, repeated “absorption and swelling–dehydration and contraction” of clay minerals leads to the repeated physical action of “squeezing–unloading” in the interior of a rock. This results in the initiation and gradual expansion of cracks in the framework mineral quartz, exhibiting failure mode from the interior to the exterior. In contrast, under the alkaline condition, the dissolution on the surface of quartz particles leads to the expansion and connection of pores, implying that the sandstone exhibits failure mode from the exterior to the interior. Moreover, the internal mechanical analysis indicates the minerals are at high pressure because of the expansion of clay minerals in the neutral solution. However, in an alkaline water environment, the extrusion pressure of framework mineral quartz decreases significantly and is not easily broken due to increased porosity. Thus, the evolution behavior of minerals in different water environments plays an important role in the damage of the rock.

This study aimed to elucidate the damage mechanism of prestressed sandstone under uniaxial compression through the distribution characteristics of meso-structures. Four prestress levels, i.e., 0MPa, 15MPa, 30MPa, and 40MPa were selected. Nuclear Magnetic Resonance and Scanning Electron Microscope techniques were employed to observe the distribution characteristics of meso-structure within rocks and to further its damage mechanism. The results show that, compare with untreated specimens (0MPa), damaged specimens by 15MPa show a more porous meso-structure due to pores/cracks propagation which occurs between skeleton minerals and filler materials. Furthermore, specimens treated by 30MPa and 40MPa show low failure strength because micro-pores/cracks initiation inside skeleton minerals causes high deterioration. By meso-mechanics analysis, particle rotation leads to pores/cracks propagation and slightly modifies the meso-structure under low-prestress conditions. With the increase of the prestress, the transgranular cracks initiation and propagation will transform the skeleton structure of rocks, leading to significant rock deterioration.

Stress is the key factor leading to rock deterioration by formation of rocks/cracks and changing meso-structures inside rocks. To explore the evolution law of rocks/cracks and meso-structures in the rock under different loads, sandstone specimens were damaged by 0, 15, 30, and 40MPa to be studied here. According to the macro-mechanical characteristics (e.g., stress-lateral strain curve, peak strength), the damaged specimens can be divided into two types: Low Damaged Specimens (LDS) (loading by 0MPa and 15MPa) and High Damaged Specimens (HDS) (loading by 30MPa and 40MPa). For the LDS, specimens damaged by 15MPa have more medium-pores and large-pores compared with initial specimens (0MPa), implying that pore/crack propagation is responsible for the low-degree damage. In addition, pore/crack propagation mainly occurs between skeleton minerals and filler materials illustrated by petrographic characteristics. Compared with the LDS, the HDS has significantly lower peak strength and higher total porosity, indicating high-degree damage. Besides the pore/crack propagation, micro-pores initiation is discovered inside skeleton minerals for the HDS, which illustrates that formation of transgranular cracks is the main factor in the high-degree deterioration of sandstones owing to transformation of skeleton structure. According to the meso-mechanics model, under low-stress conditions, particle rotation could lead to pore/crack propagation between skeleton minerals and filler materials for the LDS, but modification of skeleton structure is limited. As the stress level increases gradually, rotation of particles will gradually weaken, and particles will be under higher stress, leading to formation of transgranular cracks, resulting in transformation of skeleton structure for the HDS. Therefore, under different stresses, the meso-evolution behavior of minerals controls the evolution of pores/cracks and changes the meso-structure of rocks.

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.