The elastoplastic nonlinear softening-cracking area of surrounding rock model is analyzed. According to the entire theory
the relationship between equivalent stress and strain is deduced from uniaxial compression. Analytic formula of stress distribution and displacement in cracking area of surrounding rock. plastic softened zone and elastic zone are derived. The critical pressure that leads to yield caused by inner pressure is obtained. The analytic formula is applied x widely; and the solutions of Kastner and fully brittle medium based on ideal plastic medium are special cases.