Synergetic stiffness design method for tunnel support-surrounding rock system

Traditional passive support design methods are increasingly inadequate for complex geological conditions and high-stress environments, posing significant threats to tunnel construction and operational safety. To ensure the overall stability of the support-surrounding rock system, this study systematically proposes a stiffness design theory and a synergetic control method. First, the concept of the structural ring is introduced to quantify the self-bearing capacity of the surrounding rock, accompanied by its determination and stability analysis protocols. Based on this, deformation control standards and rock load effects are established as the foundation for structural design. Subsequently, a dynamic analysis model for the structural ring is developed, establishing a characterization method that links tunnel deformation to support stiffness. By accounting for the stiffness growth property of the support system, a design method based on the active distribution of deformation and load is proposed. This approach transcends the limitations of traditional strength-based designs that focus solely on the final structural state. Furthermore, a stiffness synergetic control model is established, integrated with a multi-objective optimization method to achieve both global safety and economic efficiency. This methodology was successfully applied to the New Badaling Tunnel, which is a super-large cross-section project, forming an active control technology framework centered on the synergy between the structural ring and the anchorage system. Finally, the technology was extended to address large-deformation disasters in tunnels under extremely high geo-stress. These research findings provide a robust theoretical basis and systematic technical support for the scientific design and safe construction of tunnels in complex environments.