Abstract:According to the entire theory of plastic mechanics,the relationship between equivalent stress and equivalent strain of circular chamber plastic zone in the complex stress state is deduced from nonlinear softening constitutive relation of rock under uniaxial compression. On this basis,the stress,strain,and displacements of elastic and plastic zone in surrounding rocks of chamber,are derived. Then the equilibrium equation of surrounding rocks,relationship between geostress and chamber displacement,and pressure equation of surrounding rocks,are obtained under corresponding conditions. The concrete formulation of carrying power of elastic zone and carrying power of plastic zone are first proposed. Because the assumed constitutive relationship agrees well with practical condition of rocks,the obtained results maybe more closely approach to corresponding actual values in surrounding rocks of chamber,compared with Fenna¢s solution that is based on ideal elasto-plastic relationship.