The Jiajin Mountain Tunnel on National Highway 351, constructed by China Railway Construction Corporation Limited, is close to opening following completion of the project.
The tunnel is the longest Class-II highway tunnel in China and the country’s first single-tube, bi-directional driving highway tunnel constructed using a combination of TBM (Tunnel Boring Machine) and drill-and-blast methods. The project spans 10.07 kilometers in total length, with the main tunnel measuring 9.35 kilometers, designed to facilitate speeds of up to 60 km/h.
Jiajin Mountain Tunnel, the longest Class-II highway tunnel in China, has been successfully completed. [Photo/sasac.gov.cn]
Located on Jiajin Mountain, the tunnel sits at an average altitude of 3,100 meters, with workers facing extremely challenging geological conditions during construction.
To overcome challenges such as a tight schedule, complex terrain and high-altitude oxygen deficiency, the construction team from China Railway 11th Bureau Group Corporation Limited conducted simultaneous bi-directional excavation, opening four additional work faces from the pilot tunnel after it was completed.
This was the first time TBM technology has been used in ordinary national and provincial trunk highway construction in China. Compared to traditional drill-and-blast methods, the TBM approach shortened the construction period by approximately 1.5 years.
Despite the high-altitude and freezing conditions, the TBM achieved daily progress of, on average, 50 meters and a monthly record of 736 meters, setting a benchmark for TBM construction.
The Jiajin Mountain Tunnel will seamlessly connect Baoxing county in Ya'an city and Xiaojin county in the Aba Tibetan and Qiang autonomous prefecture, both in Sichuan province. The current one-hour journey through Jiajin Mountain will be reduced to just 10 minutes, with year-round, all-weather accessibility unaffected by winter snow and ice.
(Executive editor: Zhu Zeya)
