Study on the Influence of Spatial Distribution of Karst Cave Groups on Tunnel Stability and Treatment Effectiveness

To investigate the stability of surrounding rock and support structures during tunnel excavation through karst cave groups, this study adopts an integrated methodology of laboratory tests and numerical simulations. The influence of cave groups with different spatial orientations relative to the tunnel (α = 90°, 45°, 0°, −45°, −90°) is systematically evaluated in terms of surrounding rock deformation, plastic zone development, and support structure loading. Results indicate that spatial orientation significantly affects rock mass stability. The cave groups positioned horizontally to the tunnel (α = 0°) induce the most extensive plastic zone penetration, representing the highest risk scenario. For this critical case, a safety distance threshold of L = 1.8D is proposed. When cavities intrude into the tunnel profile, localized deformation effects become pronounced. Remedial grouting with C25 concrete proves effective, reducing crown uplift, crown settlement, and horizontal convergence at the arch waist by 35.43%, 13.17%, and 58.09%, respectively. Under horizontal-side intrusion conditions, initial support stress increases markedly—nearly doubling compared to other orientations—necessitating targeted reinforcement measures. These findings offer practical guidance for the safe design and construction of tunnels in karst regions.