<p>The stability of deep circular tunnels is strongly influenced by excavation-induced stress relaxation and the associated damage in the surrounding rock mass. Conventional analytical and numerical methods often assume constant or simplified damage distributions, which do not adequately represent the gradual reduction of damage away from the tunnel boundary. In this study, a semi-analytical elastoplastic solution is developed by introducing a stress-dependent damage factor into the generalized Hoek–Brown failure criterion. The proposed formulation defines rock mass strength as a function of stress relaxation and damage attenuation, leading to a more realistic description of post-excavation behavior. Validation against finite element simulations shows close agreement in terms of stress redistribution and tunnel deformation. The formulation also provides a rational basis for convergence–confinement analysis by generating realistic ground reaction curves that account for continuous damage attenuation. Comparative results further indicate that, when using commercial finite element software with stepped damage models (ranging from 2 to 12 steps), increasing the number of steps tends to produce results closer to those of the proposed method. However, even after the 12-step damage model, the tunnel convergence is still overestimated. By directly incorporating continuous damage attenuation without requiring additional computational effort, the proposed model provides a more realistic, efficient, and physically consistent framework for assessing tunnel stability under high in-situ stress conditions.</p>