On March 16th, the left tunnel of the Laoying’pan No.1 Tunnel, a controlling project of the Xichang-Zhaotong Expressway, was successfully holed through, laying a solid foundation for the smooth opening of the Xichang-Zhaotong Expressway.
The left tunnel is 5,084 meters long, while the right tunnel under construction is 5,014 meters long. It is the longest tunnel in the Laoying’pan spiral tunnel group of the Xichang-Zhaotong Expressway, 627 meters longer than the current world’s longest spiral tunnel – the Hankou Tunnel (4,457 meters) of the Xinjin Expressway.
The Laoying’pan No.1 Tunnel is just part of the Laoying’pan tunnel group, which is located in the deep mountains of Jinyang County, Liangshan Yi Autonomous Prefecture, Sichuan Province. To overcome the approximate 290-meter elevation difference between the starting point of Lugaoshu Hub and the entrance of Jinyang Tunnel in this project, designers ingeniously set up the Laoying’pan spiral tunnel group and a 1.67-kilometer bridge project to centrally elevate the route, solving the short-distance route climbing challenge.
During the tunnel group design process, the design unit fully utilized its advantages in geological route selection in the complex mountainous areas of Southwest China. After repeated consideration of the crossing angles between the tunnels and the regional Choushui Well Fault, as well as the geological conditions of the tunnel entrances and exits, the minimum curve radius inside the tunnel was adjusted from 900 meters to 970 meters. This optimized the plane indicators inside the spiral tunnel, improved the crossing angle with the Choushui Well Fault, reduced the construction difficulty of the tunnel, and enhanced driving comfort and safety.
After the opening of the Xichang-Zhaotong Expressway, it will connect with the G85 Chengdu-Kunming Expressway, the Xichang-Chongqing Expressway, and others, forming a smooth and accessible route to the sea and a major tourism route out of Sichuan Province, which is of great significance for promoting the social and economic development of Sichuan Province.