视衬砌在内压力作用下与围岩共同承载联合工作，采用全量理论将岩体单轴应变非线性软化本构模型推广，得到复杂应力状态下岩体等效应力和等效应变关系，将围岩划分为松动区、塑性区、弹性区，对衬砌压力隧洞在等压荷载作用下进行弹塑性分析。在推导出围岩松动区、塑性区、衬砌内任一点的应力和位移解析计算公式基础上，得出了不同工况下围岩抗力系数计算公式，该围岩抗力系数计算公式不仅考虑了中间主应力的影响，而且与已有的围岩抗力系数计算公式相通。

According to the entire theory of plastic mechanics, the relationship between equivalent stress and equivalent strain of a surrounding rock is deduced from a nonlinear softening constitutive model of uniaxial compression. The surrounding rock is classified into loosened zone, plastic zone and elastic zone, and an elastoplastic analysis is performed for a lined pressure tunnel under the equivalent load. The displacement and stress distribution laws at the loosened zone, plastic zone and lined zone are presented. On the basis of this, the formula of rock resisting coefficient is given. The formula not only considers the intermediate principal stress effect, but also is similar to other researchers formulas.