Traditional submarine tunnels with drainage systems are highly susceptible to water leakage,which is challenging to locate and manage,leading to high maintenance costs.To address this problem,a new controlled drainage system for submarine tunnels was proposed in this study.The system utilizes a double-adhesive waterproof membrane instead of traditional waterproof sheets,which not only reduces the likelihood of leakage but also makes subsequent leak detection and repair easier.In addition,replacing blind pipes with drainage sheets significantly improves the clogging resistance of the drainage system.The influence of grouting circles and drainage sheets on the water inflow and the external water pressure on the lining was then analyzed using numerical calculation methods.Finally,the design process of the new controlled drainage system was proposed.The research suggests that the new system allows for a multi-stage control method using grouting circles and drainage sheets,providing greater design flexibility.In the primary control stage,grouting circles effectively reduce the tunnel water inflow and the external water pressure on the lining,with the permeability coefficient playing a crucial role.In the secondary control stage,the spacing and width of the drainage sheets can regulate the water inflow and pressure.Unlike grouting circles,drainage sheets decrease water pressure while inevitably increasing water inflow,and vice versa.These findings can serve as a valuable reference for the design of waterproof and drainage systems in submarine tunnels.
Due to the influence of karst cave development and route selection,the location relationship between concealed karst cave and tunnel is more random.In order to explore the influence rule of karst cave location on the minimum safe thickness of water-proof rock mass,a simplified calculation model of water-proof rock mass thickness when the karst cave is located at any location around the tunnel is established,and the influence of multiple factors on the overall stability of water-proof rock mass is considered.Based on the cusp catastrophe theory,the analytical expressions for the safety thickness of waterproof rock mass are derived.Based on the finite difference principle,the analytical expressions of the safety thickness of water-proof rock mass are verified.In order to improve the application range of the analytical formula derived in this paper,the analytical formula is optimized based on the instability principle differences between the simplified calculation model and the elastic compressive bar.The research results show that the necessary condition solution is more applicable and much safer than the sufficient condition solution.Tectonic stress,rock beam length and karst cave water pressure are significantly positively correlated with the safe thickness of the waterproof rock mass.The calculated results of the semioptimized formula and the unoptimized formula are constant values,independent of the karst cave location.While the calculated results of the fully optimized formula are variable values,correlated with the karst cave location,the thickness of the waterproof rock mass gradually decreases as the karst cave location moves from the top of the tunnel to the bottom of the tunnel.The unoptimized formula does not consider the influence of the lateral force of the rock beam,and is not suitable for the working condition with large lateral force,the calculation results of the semi-optimized formula and the fully optimized formula are not very different and are biased to safety,so it can be given priority.
