Resilient design of urban rock tunnels using prestressed support systems: Experimental study and field applications

Abstract

As the importance of urban underground infrastructure in disaster prevention and mitigation becomes increasingly evident, rock tunnels face complex geological and hazard risks. Prestressed support systems are widely regarded as an effective solution to enhance the disaster resilience of shallow-buried urban rock tunnels. However, traditional stress arch theory, which is designed for deeper tunnels, proves unsuitable for shallow environments, resulting in an underutilization of prestressed support systems in resilience-oriented designs. This study investigates how post-peak confining pressure compensation influences rock mass stability and strength, with verification from practical engineering cases. The results show that confining pressure compensation can significantly improve the residual strength and deformability of the rock mass, particularly at lower compensation stages, where the rock mass exhibits high sensitivity to changes in confining pressure. Furthermore, confining pressure compensation mitigates unloading-induced strength loss and substantially increases the post-peak elastic modulus. In practical engineering, the application of high-strength, high-toughness NPR bolt prestressed support in a shallow, large-span urban rock tunnel yielded significantly reduced tunnel crown settlement compared to conventional methods, demonstrating the feasibility and benefits of this approach. These findings reinforce the effectiveness of prestressed support in enhancing tunnel resilience and protecting urban underground infrastructure, offering valuable theoretical and practical insights for future development. The proposed post-peak confining pressure compensation theory underpins the resilient design of urban rock tunnels and provides a novel technological pathway for underground infrastructure in disaster prevention and recovery.