Nankou tunnel of Beijing-Zhangjiakou high-speed railway completed
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E-mail China.org.cn, September 14, 2018
The Nankou tunnel of the Beijing-Zhangjiakou high-speed railway was completed by the Beijing branch of China Railway Sixth Group Co. Ltd., the company said on Sept. 13.
The tunnel was the first one to be completed on the Beijing section of the railway. Located in the Nankou village of Beijing's Changping district, the tunnel is 3,032 meters in length, with the design speed of 250 kilometers per hour and a max burial depth of 340 meters.
According to the company, the geological features of the Nankou tunnel is relatively complex. The tunnel passes through three water-rich zones, with a high risk of water inrush. The maximum hydraulic discharge reaches 10,000 cubic meters. To address these complexities, the project team has invited experts to design a "super pump" so that the accumulated water and silt can be pumped out. A "stepped" drainage scheme was adopted for the backwater drainage, which helped to lay a solid foundation for the overall construction progress.
The most difficult part of construction was the cave section of the tunnel with Class IV and V wall rocks. The rocks were weather-beaten, with poor stability and weak cohesion, which caused great difficulties for the engineers. To this end, the engineers used small conduits in every cycle during the construction progress, controlled the blasting excavation footage, reduced the steel frame spacing, and increased locking anchor, so that the excavation could go on smoothly.
"Not a single incident happened during the whole construction process of the tunnel," a leader of the construction company said. "We have created a monthly record of excavating 196 meters in Beijing."
The opening of the tunnel saved much time for the subsequent construction of the ballastless track and the joint commissioning test, laying a solid foundation for the construction of the Beijing section of the Beijing-Zhangjiakou high-speed railway.
According to reports, the rail line stretches 173.96 kilometers, of which 70.50 kilometers is in Beijing and 103.46 kilometers in Hebei province. It has 10 stations in total. When it opens to traffic, it will shorten the travel time from Beijing to Zhangjiakou from 3.5 hours to about one hour.
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