| Water is one of the most active components in geological environment. Its interactions with geo-materials are not only the hydraulic effect which is correlated with the concept of effective stress, but also the effect of complicated water-rock effects. Previous studies have shown that the water-rock interactions play an important role in the geotechnical instability or failure. Moreover, with the advance of engineering technology and the scope of the deepening development of rock engineering, the coupled mechanical-hydraulic-chemical problem becomes more and more prominent. Therefore, the studies on mechanical characters of rock mass under water-rock interactions and the coupled problem of M-H-C have important theoretical significance and practical value to evaluate the long-term stability of rock engineering, such as slope, dam foundation, tunnel, underground cavern and waste disposal in environment engineering, etc.To study the stability problem in geotechnical engineerning, shear strength tests of sandstone under different hydro-chemical environments were carried out. The mechanism of hydro-chemical corrosion of sandstone was discussed. The effect of hydro-chemical action on shear strength of sandstone was analyzed and a variable was introduced to quantitatively express the hydro-chemical damage evolution of shear strength parameters. Moreover, shear rheology tests on weak structural plane of sandstone with different water contents were conducted. The effects of water content on the shear rheology behavior and long-term shear strength of weak structural plane of sandstone were analyzed, and then a modified viscoelastoplastic model was identified to describe the effects of water content on the rheology behavior of weak structural plane. A numerical model was proposed to predict the hydro-chemical damage evolution of rock. Following that, the coupled mechanical-hydro-chemical elastic and elastoplastic model were proposed respectively and the corresponding numerical simulation programs were developed. Then the stability evolution processes of a tunnel under different hydro-chemical circumstances were analyzed by both the coupled M-H-C elastic and elastoplastic methods. The main contents of the thesis are represented as follows:(1) Shear strength tests of sandstone under different hydro-chemical environments were carried out. The effect of hydro-chemical action on sandstone structure was analyzed from the viewpoint of meso-mechanism, and the mechanism of hydro-chemical damage of sandstone was discussed. On this basis, the effect of hydro-chemical action on shear strength of sandstone was analyzed, and a variable was introduced to quantitatively express the hydro-chemical damage evolution of shear strength parameters.(2) Shear rheology tests on weak structural plane of sandstone with different water contents were conducted. The curves of the shear rheology deformation vs. time under different water contents of the fillings were derived. The effects of water content on shear rheology behavior and long-term shear strength of weak structural plane of sandstone were analyzed. Moreover, the influence mechanism of water content effects on the rheological characteristics and long-term shear strength were discussed.(3) A modified viscoelastoplastic model, which based on the test results and analysis, was identified to describe the effects of water content on the rheology behavior of weak structural plane. Meanwhile, the parameters of the model were identified through back analysis by genetic algorithm.(4) A hydro-chemical damage evolution model was proposed by chemical kinetics method. Based on the model, the hydro-chemical damage evolution processes of Chongqing sandstone under different circumstances, which considered the variations of pH values, ions species and ions concentrations, were simulated. Moreover, the sensitivity of the influencing environmental factors was discussed.(5) A coupled M-H-C elastic model was proposed, which was composed by hydro-chemical damage evolution model, rock matrix constitutive model, seepage equation and pore pressure equation.(6) With modular software development method, a new program was developed to simulate the coupled M-H-C elastic model based on COMSOL and Phreeqc.(7) By introducing the concept of chemical softening, a coupled M-H-C elastoplastic model was established.(8) Based on the numerical simulation program of the coupled M-H-C elastic model, by embedding the coupled M-H-C elastoplastic constitutive model, a new program was developed to simulate the coupled M-H-C elastoplastic model.(9) The stability evolution processes of a tunnel under different hydro-chemical circumstances were predicted by both the coupled M-H-C elastic and elastoplastic methods. Then the environmental impact factors to the stability of the tunnel were analyzed.
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