China News Service, Beijing, October 7 (Reporter Zhou Rui) China Railway 22nd Bureau announced on the 7th that on the same day, as the excavator driven by the staff of the group shoveled the last piece of loess, a new Zhong (Wei) Lan ( The Panxian Mountain Tunnel, the longest loess tunnel in the Gansu section of the state) passenger train, has been completed, and the China-Lanzhou passenger train has made breakthroughs, an important part of China's "eight vertical and eight horizontal" railway network.
According to Wu Mengyu, project manager of China Railway 22nd Bureau Group, the 219.707-kilometer Zhonglan Railway is an important part of China’s “eight vertical and eight horizontal” railway network, the Beijing-Lanzhou corridor. Its northern end is connected to the Zhongwei-Wuzhong Intercity Railway and the southern end is Connecting to the Lanzhou hub will open up the bottleneck of the lack of fast passenger transport channels in northwestern China connecting north and northeast China. At the same time, it will form a fast passenger transport channel directly outside the land bridge channel in the western region to the coastal areas.
Zhou Guangyi, chief engineer of the Project Department of China Railway 22nd Bureau Group, said that the Lanzhou loess in the Gansu section of the Zhonglan Passenger Train is the thickest aeolian loess development area in China.
Among them, the upper and lower silt layers in the loess layer are the biggest difference from other regional loess.
The geology of the pipeline section of the project department is dominated by Lanzhou loess, with typical upper and lower silt sand layers, which is the source of frequent geological disasters in related areas.
Among them, the Panxian Mountain Tunnel with a total length of 2,829 meters has poor geological conditions such as loess caverns, shallow slips and silt sand layers, and has low bearing capacity. It is one of the two high-risk projects on the entire line and is listed as the highest in the country by the National Railway Group. Risk engineering.
It is also the throat of the girder channel on the entire line, and is the most difficult key control project for the entire line.
According to reports, in the face of challenges such as 11 caverns and 4 shallow slumping, as well as risks such as sand leakage, sand gushing, large settlement, and surface cracking and subsidence, the technical team of the project department vigorously carried out scientific research.
At a distance of 45 meters from the tunnel entrance, the technicians discovered that a layer of silt and fine sand began to appear on the face of the tunnel, which was subsequently expanded to a full section. The length of the silt and fine sand layer was about 255 meters and the maximum buried depth was 45 meters.
Faced with the difficulties encountered in the construction process, the technical team and relevant experts repeatedly surveyed and tackled key problems jointly, following the construction of "pipe advancement, short footage, strong support, fast closure, early ring formation, strict grouting, and frequent measurement" According to the principle, the technology of "three-step temporary inverted arch + vertical support" and other four construction methods was finally innovated to solve this problem, and the monthly footage was increased from 10 meters to 20 meters.
The Project Department of China Railway 22nd Bureau Group stated that at present, the department has innovated a number of technological methods and formed a complete set of technical achievements in China's construction of tunnels in silt loess.
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