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.