## 2 Physical and Mechanical Properties of Rock Mass Under THMC Coupling
### THMC Coupling Test of Deep Rocks  
Deep rocks, subjected to high temperature, significant osmotic pressure, intense geostress, and complex hydro-chemical environments, experience multi-field (THMC) coupling effects that involve interactions between temperature, water flow, stress, and chemical processes. This intricate coupling process is central to current research in rock mechanics, as illustrated in Figure 6. The multi-field coupling in rocks incorporates various interrelated phenomena: the influence of temperature on mechanical properties, the stress response of fractured rock masses, fluid flow dynamics within rock structures, and the chemical reactions between water and minerals. Given this complexity, extensive research is required to understand the rock failure evolution and deformation mechanisms under these multi-field coupling conditions. As illustrated in Figure 6, the coupling relationships among THMC fields exhibit several characteristics [14; 104; 105]. First, mineral dissolution and precipitation processes alter porosity and permeability in porous media, affecting fluid flow. Second, chemical reactions that absorb or release heat modify thermal field characteristics. Third, mineral dissolution impacts the mechanical state of the medium by influencing its physical parameters. The impact of the hydraulic, thermal, and mechanical fields on the chemical field is primarily  
Figure 5: General description of fractured rock mass deformation [141]. (**a**) Effective confining pressure, (**b**) volume deformation, (**c**) shear deformation, (**d**) effective normal stress, (**e**) normal deformation of fracture, (**f**) and tangential deformation of fracture. observed in three aspects [106; 107; 142]: (1) fluid velocity in the hydraulic field influences solute transport rates, (2) temperature affects reaction rates, and (3) structural changes in porous media due to mechanical stress alter solute concentration and mass transfer rates. When studying multi-field coupling in rocks, the definitions and priorities can differ across industries. For example, in water-force coupling, different concepts emerge depending on the focus, such as fluid-structure interaction, water-rock interaction, or simply water-force coupling. Fluid-structure interaction focuses on the mechanical interaction between solid materials and fluids, whereas water-rock interaction emphasizes the chemical reactions between water and rock minerals [94; 95; 96]. Water-mechanical coupling, on the other hand, primarily investigates how water and stress jointly influence the mechanical behavior, deformation, and failure patterns of rocks. In areas like nuclear waste disposal and deep coastal mining, research on multi-field coupling goes beyond water-force interactions, focusing on the combined effects of temperature, water, stress, and chemical fields [143; 144; 145; 146; 147; 148; 149; 150; 151; 152; 153; 154; 155; 156; 157; 158]. Testing such interactions in situ requires long-term systematic experiments that integrate stress, temperature, water flow, chemical, and damage fields. These studies aim to establish constitutive relationships for multi-field coupling and advance numerical simulation techniques to analyze the interdependencies among the various fields. [PERSON] [159], for instance, conducted uniaxial and triaxial creep tests on salt rocks under different stresses, confining pressures, and temperatures. His experiments revealed the relaxation characteristics of the rocks and led to the development of creep failure criteria. [PERSON] [160] studied the rheological behavior of deep rocks in South African gold mines at depths exceeding 2000 m. Even in hard quartzite and igneous rocks, rheological effects were significant, with steady-state creep rates surpassing 0.7 m\(\cdot\)h\({}^{-1}\). Similarly, [PERSON] et al.