The traditional method which focuses on displacement

stress and yield zone has some difficulties in stability and reinforcement analysis during excavation in underground engineering. The deformation reinforcement theory mainly discusses the optimal reinforcement force required by the structure to keep stable when it bears load which is beyond the limits of the load bearing capacity. It notes that for the structure under the action of a given load

the area where unbalanced forces exist is the location of initial failure occurs; structure under a given load reinforcement force always tends to minimize the reinforcement force and maximize self-bearing. The whole stability can be judged by plastic complementary energy norm quantitatively. Two important concepts of deformation reinforcement theory

unbalanced force and plastic complementary energy norm

are deducted and illustrated based on 3D nonlinear finite element method. Through two typical examples of tunnel and roadway in deep rock

the distribution of unbalanced force and the plastic complementary energy norm of surrounding rock before and after the reinforcement have been analyzed. The results show that the reinforcement of the surrounding rock can improve the strength and the bearing capacity

and the deformation reinforcement theory based on nonlinear calculation is effective for analyzing stability and reinforcement of underground structures.