On July 9, 2020, with the last cannon, the key control project of the entire railway line from Dali, Yunnan to Lincang, constructed by China Railway 10th Bureau, Hongdou Mountain Tunnel, was successfully opened, marking the first domestic and rare toxic and harmful gas in the world. The tunneling problem was successfully solved, laying a solid foundation for the early opening of the Dalin Railway.

Hongdou Mountain Tunnel is located in Fengqing County and Yun County of Lincang City, with a total length of 10,616 meters and is adjacent to the Lancang River. The geographical environment is extremely complex. It is the only one encountered in China's railway construction that has collected 8 kinds of toxic and harmful gases and has a long distance. A large tunnel with strong water inrush, high ground temperature, and alteration of granite in long sections.

The tunnel started construction in May 2016, and in June 2017, eight harmful gases such as hydrogen sulfide and carbon dioxide were found in the tunnel. There are many types of harmful gases, high concentration, and great degree of hazards. The extremely dangerous areas of toxic and harmful gases are up to 4210 meters, the dangerous areas are 3630 meters, and the dangerous areas above the height account for 73.8% of the total length of the tunnel. And challenge. The tunnel also encountered a high temperature area of nearly 40°C. During the construction process, a large number of ice cubes need to be transported out to cool down. Workers often wear high temperature and wear gas masks for construction.

Since there is no construction experience to learn from, the construction unit has repeatedly invited well-known experts in the petroleum, coal mine and other industries to conduct on-site surveys and hold expert meetings to study the treatment plan of harmful gases. At the same time, they set up a "special geological specialty research internship base" in Hongdoushan Tunnel, organized managers and operators to learn together, mastered the knowledge of prevention of harmful gases, and discussed specific construction methods and process standards. After repeated verification on site, the construction unit has formed a set of control standards and construction methods for a variety of harmful gases, and successfully solved the problems of high concentration of harmful gases and large risk factors in tunnel construction.

As a key project to improve the national railway network in the west, the construction of the Dalin Railway is in full progress. All participating units are working overtime and overtime to fully promote the remaining projects. At present, 99% of the roadbed is completed, 98% of the bridges are completed, and 98% of the tunnels are completed. All work was carried out in an orderly manner in accordance with the construction plan.

The Dali Railway runs from the Dali Station on the vast line to the north. It crosses the Lancang River from Dali Prefecture to Lincang City. The total length of the line is 202 kilometers and the design speed is 160 kilometers per hour. After the Dalin Railway was completed and opened to traffic, Dali to Lincang will be compressed from the current road transportation of nearly 5 hours to 1.5 hours, ending the history of Lincang City with no railways. Editor/Peng Xue