Abstract: Based on a program for geotechnical engineering, the functions of modeling reinforcing bar and cracking of concrete are supplemented; and a corresponding nonlinear FEM program is developed. The combination of cracking and plasticity in iterative calculation has also been achieved. Then, in accordance with the practice of a diversion tunnel for a certain hydropower station, the whole procedure consisting of construction, operation and plugging has been analyzed. The process shows that the algorithm routine has good stabilization and convergence, and can meet the requirement of accuracy. The results show that the crack extent, the crack width and the reinforced bar stresses increase with the increment of the original gap width in the operation; and the plastic zone in rock increases with the rising of the outside water level. So some measures should be taken to keep the rock stable in plugging time.

Key words: hydraulic tunnel, reinforced concrete lining, nonlinear FEM, yield criterion