Abstract：The reinforcement theory considering deformation mechanism of rock mass is proposed and authors. The main ingredient of the theory is that the unbalanced forces of a deformable body in elasto-plastic elaborated. calculation are just the required reinforcement forces，and the elasto-plastic calculation always tends to minimize the unbalanced forces. It is revealed that the reinforcement theory is based on the so-called non-equilibrium elasto-plastic mechanics，which leads to the minimum plastic complementary energy principle for the corresponding unstable structures. Case study on an arch dam shows that the distribution of unbalanced force is helpful to evaluate the structural stability and reinforcement.
