## 1 Introduction  
With the planning and construction of large-scale hydropower station clusters in southwest China, both the project scale and dam height are being constantly refreshed. The mechanical properties of the deep rock mass under the high hydraulic pressure environment have changed significantly, which in turn leads to engineering problems such as valley deformation and dam face cracking [1, 2, 3]. The lack of systematic mastery of the deformation characteristics of deep rocks under a high water pressure environment has become a technical bottleneck restricting the safe operation of large hydropower stations. Therefore, the study of the effects of the water environment on rock engineering remains a long-term and valuable scientific problem. Numerous scholars have carried out some meaningful research on the mechanical properties and deformation behaviors of rocks under water and water pressure. [PERSON] et al. [4] carried out scanning electron microscopy and uniaxial compression tests on siltstones with a water content of 0%, 0.5%, 1.5%, and 2.8%, respectively, and the results showed that the strength and deformation parameters of siltstones were weakened to varying degrees after water absorption. [PERSON] et al. [5] investigated the weakening effect of water on rock brittleness from an energetic point of view, and the results showed that in the presence of water, the energy storage capacity of hard rock decreased due to the dissipation of internal elastic energy in the compression stage. [PERSON] et al. [6] conducted static-dynamic-coupled loading tests on dried water-bearing sandstone specimens with axial prestresses ranging from 0 to 62.5 MPa, and the results showed that for each prestressing force, the dynamic strength of both the dried and saturated specimens increased with increasing strain rate. [PERSON] et al. [7] studied the effects of porosity and hydration on the tensile and compressive strengths of sandstones and showed that water saturation reduced the strength of the rocks by about 20%. [PERSON] et al. [8] investigated the weakening effect of water in the brittle fracture and fracture flow states of sandstones and showed that the reduction in the brittle strength of sandstones in the presence of water was in the range of 5% to 17%. [PERSON] et al. [9] conducted a series of triaxial compression tests under hydrodynamic coupling conditions in order to investigate the influence of perimeter pressure and pore water pressure on the strength characteristics of deep sandstones, and the results showed that the peak stress of sandstone increased with the increase in perimeter pressure, while the presence of pore water pressure could weaken the peak stress of sandstone. [PERSON] et al. [10] investigated the effect of pore pressure on the plastic deformation damage of water-saturated tuff. [PERSON] and [PERSON] [11] conducted a series of mechanical tests on three kinds of rocks under different water pressures in order to study the effect of real water-rock interaction on the mechanical behavior of rocks, and the results showed that the stress-strain curves of the saturated rocks increased and those of the dry rocks decreased and then increased with the increase in water pressure. Specifically, the peak stress and modulus of the elasticity of saturated rocks increased linearly when the water pressure increased, while the peak stress and modulus of the elasticity of dry rocks decreased first and then increased sharply. Previous studies have shown that the presence of water leads to the deterioration of the mechanical properties of rocks and alters their physical properties, mainly due to the weakening of the rock forces by water [12; 13]. Weakening mechanisms include the reduction in fracture energy, the reduction in friction coefficient, the reduction in capillary tension, stress corrosion, and chemical and physical deterioration [14].