At 10 A.M. on April 25th, as the surrounding rock of the last meter of the tunnel arch was drilled through, Yuelongmen Tunnel of the Chengdu-Lanzhou Railway was successfully penetrated after ten years, laying a solid foundation for the opening of the Chengdu-Lanzhou Railway.

The completion site of Yuelongmen tunnel of Chengdu-Lanzhou Railway

The Chengdu-Lanzhou Railway is an important part of the Lanzhou-Guangzhou corridor of the national "eight vertical and eight horizontal" high-speed railway planning network, with a design speed of 200 kilometers per hour. Yuelongmen Tunnel, built by China Railway 19th Bureau Group Co., Ltd., is located in Gaochuan Township, Anzhou District, Mianyang City, Sichuan Province, and Tumen, Maoxian County, Aba Prefecture. It is a twin-line tunnel built separately, with left line length of 19.981 KM while right line length of 20.042 KM. As the longest ridge tunnel in Longmeng Mountain area, it crosses the Longmen Mountain Range and has a maximum buried depth of 1445 meters. The level difference between entrance and exit is 346.3 meters.

Drilling jumbo under operation

Yuelongmen tunnel is located in the Wenchuan earthquake disaster core area.The steep terrain, large height disparity between ridge and valley and frequent geological disasters make it one of the most difficult ridge tunnels of railways under construction in China. Four national records are created: the largest auxiliary tunnel scales, the longest section of early Paleozoic age non-coal harmful gas release, the longest deformation section formed by Cambrian high stress soft rock five million year ago, the longest space-time through geological strata by single tunnel.

Drilling for blasting

According to Mr. Wang Hailiang, Project Manager of Chengdu-Lanzou Railway Project from China Railway 19th Bureau Group Co., Ltd., Yuelongmen tunnel is of extremely high risks with varied adverse geological complexities, mainly including high crack seismic fracture zone, karst water rich zone, under-crossing of riptide and gullies, high ground stress, high ground heat, soft rock deformation, rock burst, etc. The tunnel is also filled with hazardous gases like high gas and hydrogen sulfide. The participants of the project have originally developed “Ventilation Technology for Staged Dynamic Construction of Extra-long High Gas Tunnel”, in which a 9-level ventilation system is established, completely solving the problems of ventilation safety and high gas control for extra-long and complicated tunnel construction. In view of the large deformation area, they explored the tunnel mechanization configuration and supporting construction system of "fast tunneling, fast supporting, fast closure, high quality, good safety, beautiful appearance and fine maintenance". The original invention of construction method by two-step with inverted arch for fast tunnel closure has ensured the smooth completion of the tunnel.

After opening of Chengdu-Lanzhou Railway, the history of northwest regions of Sichuan Province without railway will be ended. With existing Baoji-Chengdu Railway, Lanzhou-Chongqing Railway and Chengdu-Xi’an Railway, they will form the trunk railway network connecting Northwest, Southwest and South China, playing important strategic roles for overall regional economic and social coordinated development, and ethnic region unity and progress. 

（Translator: Hou Chao）