针对地下洞室开挖扰动分析中常忽略应力主轴旋转以及应力扰动无法量化的现状，以大岗山水电站地下厂房为研究实例，根据主应力方向与洞室横断面及洞轴线之间的几何关系，定义了描述应力主轴旋转的特征角。研究表明，洞室开挖引起了顶拱和边墙不同程度的应力释放和主方向旋转，围岩主应力均在开挖当期卸荷强烈，主应力方向在开挖当期和后继一个开挖期中旋转强烈，且顶拱和边墙部位主应力方向调整具有一定的共性，表现为最小主应力方向最终近似垂直于洞室开挖面，而最大主应力与中主应力方向则近似在平行于开挖面的平面内调整。在此基础上，考虑应力主轴旋转影响，定义应力扰动指标SDI作为描述洞室围岩应力场扰动程度的力学表征量，研究了大岗山水电站地下厂房围岩应力场扰动的时间演化过程和空间分布特征，并将数值模拟得到的强应力扰动区与现场测试的开挖损伤区进行了对比分析，相关认识和结论具有一定理论和工程意义。

Based on the underground powerhouse of Dagangshan Hydropower Station, the characteristic angles according to the geometric relationship between the principal stress direction and the cavern space position are defined, in order to describe the rotation of the principal axes of stresses. The research shows that different degrees of stress release and principal axis rotation are induced in the arch and the side wall during the excavation. The principal stresses in surrounding rock unload intensely in the current excavation, while the direction of principal stresses rotates violently in the current and subsequent excavation stages. Furthermore, the principal stress direction adjustment has certain similarities in the arch and the side wall. The final direction of the minimum principal stress is approximately perpendicular to the cavern free surface, and the directions of the maximum principal stress and intermediate principal stress are adjusted almost parallel to the excavation surface plane. On this basis, considering the effect of principal stress rotation, the stress disturbance index (SDI) is defined as a mechanical characterization quantity, and using it to describe the disturbance degree of stress field in the surrounding rock. SDI is applied to study the time evolution, along with the space distribution characteristics of stress field disturbance in the underground powerhouse of Dagangshan Hydropower Station. The strong stress disturbance zone obtained by numerical simulation is compared with the excavation damaged zone by field test, and the related understanding and conclusions are of certain theoretical and engineering significances.