Analysis and optimization of surrounding rock stability for an ultra-deep underground cavern group using peridynamics

• A state based peridynamics simulation method was proposed to predict the excavation damage zone of ultra-deep underground caverns. • The influence of overburden depth, lateral pressure coefficient, cavern spacing and excavation sequence on the excavation damage zone has been studied. • Revealed the deformation and damage evolution laws of the surrounding rock of the ultra-deep underground cavern group, and provided reference for design optimization. With the continuous advancement of hydropower projects toward greater depths, controlling the stability of surrounding rock in underground cavern groups under complex geological conditions has become a core issue in the safe construction of deep underground engineering. To address this, a peridynamics simulation method is established for the excavation and unloading process of ultra-deep underground cavern groups, enabling accurate description of the damage and deformation characteristics of surrounding rock during excavation. Engineering-scale simulations of the step excavation process are carried out, and the evolution patterns of multiple field information such as displacement and damage are analyzed. Furthermore, excavation process simulations under various working conditions are conducted. By comparatively analyzing the distribution characteristics of excavation damage zones and displacement fields under different influencing factors, the effects of overburden depth, lateral pressure coefficient, cavern spacing, and excavation schemes on surrounding rock stability are revealed. The results provide a scientific basis for the design optimization and stability prediction of ultra-deep underground cavern groups.