On April 26, it was learned from the Chengdu-Lanzhou Railway Co., Ltd. that at 9:58 a.m. on the 26th, as the last half meter of arch crown surrounding rock was cut through, after nearly 3,000 days of arduous efforts, the Liutongzhai Tunnel on the Chengdu-Lanzhou Railway was successfully holed through. This marks that the Maoxian-Songpan section of the Chengdu-Lanzhou Railway has entered the sprint stage, laying a solid foundation for the full completion of the Chengdu-Lanzhou Railway.

The Liutongzhai Tunnel is located in Weimen Town and Goukou Town, Mao County, Aba Prefecture, Sichuan Province. It was designed by China Railway Eryuan Engineering Group Co., Ltd. and constructed by China Railway 12th Bureau Group Co., Ltd. and China Railway Tunnel Group. The tunnel has a total length of 16.312 km, with a maximum burial depth of 1,410 m, and nearly 11 km of the tunnel has a burial depth of more than 500 m.

According to Zhou Yuefeng, project manager of the Chengdu-Lanzhou Railway project of China Railway Eryuan Engineering Group, the Liutongzhai Tunnel is one of the tunnels with the most severe large deformation of soft rock on the Chengdu-Lanzhou Railway. To reduce construction and operation risks, the design adopted a dual-tube separate construction scheme.

Yang Wei, chief engineer of the Chengdu-Lanzhou Railway project of China Railway 12th Bureau Group, said that the geological and topographical conditions of the Liutongzhai Tunnel are extremely complex, with the notable characteristics of “four extremes and three highs.” The four extremes are: extremely intense terrain dissection, extremely complex and active structural conditions, extremely weak and broken lithological conditions, and extremely significant Wenchuan earthquake effects. The three highs are: high crustal stress, high seismic intensity, and high geological disaster risk.

Xiao Xialin, deputy commander of the Chengdu-Lanzhou Command of Chengdu-Lanzhou Railway Co., Ltd., said that during construction the project department adopted a triple-span extra-large open tunnel with high-pier foundations to jointly protect the bridge, platform, station operation room, etc., and used innovative solutions such as dam-shaped hollow foundations and externally suspended formwork trolleys to solve the difficulties of building large open tunnels under conditions of weak foundations and existing bridges. In controlling large deformation, active control technology was adopted, and a series of large-deformation treatment technologies were innovatively proposed, including the combination of long and short anchor bolts and the rapid closure method for large-section excavation, solving the problem of large deformation of nearly 5 km of soft rock.

The Chengdu-Lanzhou Railway is an important part of the “Lanzhou-Guangzhou” corridor in the national “eight vertical and eight horizontal” high-speed railway planning network. It is designed for a speed of 200 km/h and is another “sky road” built on the 3,000-meter plateau in China after the Qinghai-Tibet Railway.

After the Chengdu-Lanzhou Railway is completed and opened to traffic, it will end the history of no railways in northwestern Sichuan and, together with the existing Baocheng Railway, Lanzhou-Chongqing Railway, Sichuan-Tibet Railway, and Chengdu-Xi'an Railway, jointly build a trunk railway corridor connecting the northwest with the southwest and the southern and eastern coastal areas.