Coupled hydromechanical model of unsaturated media is used to analyze the diversion tunnel #2 excavation located at the Nuozaidu Hydropower Station in China; part of tunnel site in jointed rock mass zone and water pressure around the tunnel is high. The effects of high water pressure and jointed rock mass zone during tunneling are discussed in detail. The jointed rock mass zone contains two sets of high density of parallel joints

which could be simulated by anisotropic joint constitutive model. Excavation-induced permeability changes and draining-induced saturation and permeability changes are taken into consideration. The transient coupled hydromechanical model could simulate a rapid local pressure increase

effective stress decrease

permeability changes and stability improves on excavation disturbed zone (EDZ) around tunnel during construction. Results from numerical model matches some similar foreign general experiment conclusion; and the model could be used to assess rationality and economical efficiency of tunnel construction under high water pressure condition.