<p>The quantitative determination of the disturbance factor and the excavation damage zone (EDZ) is of great importance for increasing the reliability of the excavation design and the reinforcement of the cavern. The paper proposes a comprehensive method for the quantitative estimation of the disturbance factor and the EDZ based on the acoustic P-wave velocity and the rock fracture degree (RFD) index of the surrounding rock. The optimized disturbance factor value is then used to modify the Hoek–Brown failure criterion to determine the mechanical parameters of the surrounding rock. Subsequently, the proposed method is applied to evaluate the fracture mechanism and EDZ of the rock anchor beam during excavation. It was found that the stress concentration and RFD occurred in the upstream spandrel and downstream arch foot of the cavern. The EDZ depth and RFD of the downstream sidewall are greater than those of the upstream sidewall. The evaluation results obtained by this method agree well with the deformation and macroscopic failure observed in the rock masses. The results of the research have important implications for the design optimization and stability assessment of the highly stressed caverns.</p>