A Stress-Relief Concept and Its Energy-Dissipating Support for High-Stress Soft-Rock Tunnels

When tunnels pass through high-stress, weak, and fractured rock layers, conventional rigid supports often struggle to resist the significant loosening pressure and deformation pressure from the surrounding rock, leading to various large deformation disasters. To address the limitations of support control in high in situ stress soft-rock tunnels, this study proposed a stress-relief concept for the surrounding rock based on the convergence–confinement method. An analytical elastoplastic model and a parameter selection approach for support design were developed accordingly. Guided by the mechanical behavior of tunnel supports under this concept, a novel circumferential yielding element with friction reduction and energy-dissipation capabilities was designed and validated through laboratory tests. Unlike previous reinforced or yielding support approaches, the proposed method provides a synchronized reduction in support resistance with surrounding-rock stress release, offering a fundamentally different and more adaptive deformation-control mechanism for high-stress soft-rock tunnels. Field applications were conducted in the asymmetric large-deformation section of the Qiaojia Tunnel, where full-face monitoring determined the design parameters of the energy-dissipating support (EDS) system. Field test data show that, compared with conventional rigid supports, the proposed system can effectively control asymmetric deformation, reducing the surrounding rock pressure difference between the left and right tunnel shoulders from 0.84 MPa to 0.23 MPa, highlighting its advantages for stabilizing high-stress soft-rock tunnels. The results provide a practical framework for designing adaptive support systems that combine controlled yielding and energy dissipation.