关角隧道9#斜井工区为高地应力软岩区段，开挖后洞室变形较大、稳定性差。文章首先根据理论公式分析了影响洞室变形和塑性区大小的主要因素，而后针对碳质板岩段，采用数值计算的方法具体分析了岩体变形、强度参数、地应力特征、开挖断面形式以及支护刚度等因素对洞室变形的影响；最后结合不同开挖断面形式和不同支护刚度的现场试验，提出了考虑地质环境、洞室形状和支护特征的隧道洞室支护体系评价指标F，并采用该指标对碳质板岩段支护体系进行了评价，其结果与变形等级有较好的对应关系。该指标对于设计阶段隧道支护体系的评价有一定的参考价值。

There exists some 1 000 m carbonaceous slate stratum under high geostress in the 9th inclined shaft work area of Guanjiao tunnel. The slate rock mass is weak, which would result in large deformation after excavation. Firstly, the main factors influencing the deformation of the tunnel and the plasticized zone of the surrounding rock are generally analyzed based on theoretical formula; Secondly, factors influencing the stability of the slate tunnel section, such as the parameters of the deformation and the strength of the rock mass, the geostress characteristics, the crosssection shapes and the support rigidity, are analyzed in detail by means of numerical simulation; Finally, a comprehensive evaluation index F is proposed based on the above analysis and the field experiments on the different crosssection shapes and different support rigidities. The index, which comprises geological condition, excavation crosssection shapes and support rigidity, is applied to evaluate the support of the tunnel in carbonaceous slate. The evaluation results coincide well with the deformation grade. The index can provide reference for the support system evaluation in the tunnel design stage.