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In situ stress and underground water are known to significantly influence the deformation and stability of deep underground caverns. These factors should be considered in the design of excavation and supporting schemes. However, the rock failure mechanism and permeability characteristics under the coupling condition remain largely unexplained. Based on the Xianglushan diversion tunnel in Central-Yunnan Water Diversion Project, we conducted triaxial compression experiments on both intact rock specimens and cracked rock specimens with three confining pressures (11 MPa, 18 MPa, and 25 MPa) and three osmotic pressures (2 MPa, 6 MPa, and 10 MPa). The experimental results show that rock strength can be expressed as a function of confining pressure and osmotic pressure. Osmotic pressure can reduce rock strength, while the effect of confining pressure is opposite. With the increase of osmotic pressure, the initial permeability and the peak permeability increase. Compared with the stress-strain curve, the variation of permeability-strain curve is “hysteretic.” For cracked specimens, the stress-strain curve after failure presents a “step down” trend, and the permeability-strain curve appears a “bimodal shape.” The failure pattern changes from shear failure to tensile failure as the osmotic pressure increases. With the increase of osmotic pressure, the crack increases gradually and becomes tortuous and rough. The generation and propagation of cracks gradually develop towards vertical load.

Modern tunnel support design theory holds that surrounding rock not only generates load, but also takes load together with support system. However, how much loads will be taken by surrounding rock and support system respectively is still not clear. In order to investigate the cooperative effect of rock-support system for deep tunnel in complicated rock strata, we performed a true three-dimensional geo-mechanical model test to simulate tunnel construction crossing a weak fault based on the engineering background of Xianglushan Tunnel of Yunnan Water Diversion Project in China. Our test results reveal that: (1) the mechanical behavior of surrounding rock is influenced by the lithology. The evolution and distribution characteristics of displacement and stress are significantly different in various rock strata; (2) weak fault has little influence on the proportion of load taken by surrounding rocks, but has a distinct impact on the proportion of loads taken by supporting system components. Surrounding rock is the absolute dominant load-bearing body, taking about 97% of the excavation-induced load; (3) the bearing capacity of bolt is weak, and its main function is to reinforce surrounding rock. The lining is mainly used to bear load. Test results obtained in this study can provide important physical basis for the development of the construction scheme and the optimization of support design. These results can also serve as the benchmark for the validation of numerical models.