Abstract: Based orithe unified strength theory，the formula for calculating rock resistant coefficient is given in the paper,which can be adopted to consider the intermediate principle stress effect and to obtain rock resistant coefficient in other situations or strength thoeries simply by as． sumed the parameter in the formula．So the formula can be applied in kinds of rock conditions．

Key words: unified strength theory, rock resistant coefficient, rock mechanics, intermediate principle stress effect

摘要： 基于统一强度理论，本文推导得到围岩抗力系数计算公式，该公式具有可以考虑中间主应力的影响以及修改 参数后可以退化为其他围岩条件或者其他强度理论条件下的围岩抗力系数计算公式等优点，具有较强实用价值．

关键词: 统一强度理论, 围岩抗力系数, 岩石力学, 中间主应力效应