On January 11, with a roaring blast, the single-tube excavation of the right tube of Jiufeng Mountain No. 2 Tunnel successfully exceeded 1,000 meters. Jiufeng Mountain No. 2 Tunnel is a key project of the Hebijin Expressway and also the only tunnel quality engineering demonstration site designated by the Ministry of Transport in Chongqing. At present, the cumulative excavation of both directions of the tunnel has reached 1,800 meters, completing 40% of the entire tunnel construction.

“What is being carried out now is concrete spraying. This is a wet spraying manipulator, which can ‘spray exactly where needed’,” said Chen Lin, deputy director of the project engineering department. It is understood that the two wet spraying manipulators used in the project can not only increase efficiency by two to three times, but also be operated remotely, reducing the safety risks of crossing adverse geological conditions such as sudden mud and water inrushes.

Jiufeng Mountain No. 2 Tunnel has a total length of 2,230 meters. The crossing area contains adverse geological conditions such as sudden mud and water inrushes, corrosive groundwater (rock and soil), karst, gas, goaf and old kiln water accumulation, and swelling surrounding rock. The tunnel is designed as a single-tube three-lane tunnel with a large excavation span (maximum excavation span of 21 meters), greatly increasing the excavation risk. How to overcome these difficulties? Liu Fan, chief engineer of the project, said that in response to these challenges, the project actively innovated by using advanced technologies such as TSP, MMS, 3D imaging, advanced drilling machines, and geological radar to detect the surrounding rock ahead of the tunnel, ensuring tunnel construction safety. At the same time, the method of two-way excavation with four working faces excavated simultaneously was adopted to ensure synchronous control of safety, quality, and construction progress. At present, excavation is advancing at an average speed of 10-12 meters per day.

Jiufeng Mountain No. 2 Tunnel starts in Longdong Village, Tongliang District, Chongqing, and ends in Liangshui Village, Bishan District, Chongqing. It is an important passage connecting Tongliang and Bishan. The right tube of Jiufeng Mountain No. 2 Tunnel is scheduled to be completed by the end of August this year.

The Hebijin Expressway is the “Sixth Connecting Line” among the “Three Rings, Twelve Radials, and Seven Connecting Lines” in the Chongqing Expressway Network Plan (2013-2030), with a total length of 94.857 kilometers. After the project is completed, the detour distance along the entire route will be reduced by up to 65 kilometers, closely linking the Chengdu-Suining-Chongqing development belt, the Chengdu-Neijiang-Chongqing development belt, and the Yangtze River development belt, which is of great significance for promoting cooperative development in the Chengdu-Chongqing region.