Investigation of a new reverse drainage construction and the pressure-reducing effect of a tunnel in a water-rich karst location

It is quite simple to create cracking, leaking, and other disasters in the tunnel during operation because waterrich karst tunnels are subject to the action of the high head. If the drainage is not timely, this results in highpressure water collection around the tunnel lining. The study was conducted depending on Tongzi Tunnel to resolve the issue of water pressure encountered by water-rich karst tunnel lining under high head action and to lessen the issue of operational tunnel illness under long-term water pressure. The mechanical reaction of the number of reverse drainage holes and the size of pipe diameter at the raised arch under various water heads on the tunnel construction was studied using model testing in combination with numerical simulation analysis. It was discovered that using the traditional drainage system would subject the supine arch to extremely high-water pressure, which is often hard to efficiently remove. The major issue causing the elevated arch bulging tragedy is that water pressure in the elevated arch increases as head height increases. High water pressure in the raised arch may be efficiently dealt with using the suggested reverse drainage approach. The pressure reduction rate compared to the traditional drainage method achieved 13.6 % for the investigation of the fractured Tongzi tunnel reverse drainage holes, which had a total of five holes with a diameter of roughly 100 mm. Reverse drainage structures have the potential to save project costs while also realizing "point to point" pressure reduction at the elevation arch of the tunnel and have positive effects on total tunnel pressure reduction. The study's findings can serve as a guide for designing and building comparable water-rich karst tunnel constructions as well as for maintaining drainage systems while they are in use.