The widest tunnel across the Yangtze River has a diameter of 15.2 meters.

　　Xinhua News Agency, Wuhan, February 20th (Reporter Liao Jun) The "Sanyang" shield machine with a total weight of 4,400 tons keeps moving forward 24 hours a day, and more than 500 subway builders stick to their posts and work overtime day and night … … The widest tunnel in the Yangtze River — — Wuhan Metro Line 7 successfully crossed the bottom of the Yangtze River during the Spring Festival, and is expected to open for operation this year.

　　Wuhan Metro Line 7 runs from Yezhi Lake to Dongfang Macheng, with a total length of 30.85 kilometers and 19 stations. It passes through Dongxihu District, Jianghan District, Qiaokou District, Jiang ‘an District, Wuchang District and Hongshan District, and is currently under construction.

　　Zhou Shaodong, chairman of Wuhan Metro Group, said that the cross-river tunnel on Line 7 is the first cross-river shield tunnel jointly built by public railways in China. It is located between wuhan yangtze river bridge and Qingdao Road Yangtze River Tunnel, with a total length of 2,950 meters and a tunnel diameter of 15.2 meters, which is more than twice that of Metro Line 2. The excavation area of single-tube shield section reaches 195 square meters, which is 6 times that of Line 2 and Line 4.

　　The reporter visited the construction site and found that the temperature in the tunnel was obviously higher than the ground. Although walking in the tunnel in the cold winter, the whole body was sweating. The closer to the front end of the shield machine, the higher the temperature, which is close to 30 degrees Celsius, which is equivalent to early summer, and the staff only work with their clothes on.

　　Behind the roaring "monster" of the shield machine, the internal structure of the tunnel is constructed simultaneously. The circular tunnel is divided into three layers: the upper layer is the highway flue; The middle layer is a three-lane highway layer; The subway runs in the middle of the lower floor, and there are escape passages, pipeline corridors and smoke exhaust passages on both sides. Every step forward of the shield machine, segment assembly, tunnel grouting and the concrete structure of the highway layer at the rear will follow, and the material transportation at the rear will continue.

　　Ni Zhengmao, project manager of Sanyang Road Yangtze River Tunnel of Wuhan Metro Group Project, said that since the launching of the river-crossing shield, it has encountered a worldwide geological problem — — The stratum is "sticky cake layer" with "soft top and hard bottom", mixed with mudstone that expands greatly when it meets water, so it is extremely difficult to drive. Up to now, nearly 3000 knives have been replaced. During the peak period, the whole cutter will be replaced in two or three days on average.

　　In order to ensure the smooth operation of Line 7 at the end of the year, more than 500 builders from different provinces fought day and night at the cross-river tunnel site during the Spring Festival.

　　Ni Zhengmao said that the "Sanyang" shield machine is responsible for the excavation of the right-hand tunnel in the river-crossing section. At present, it has accumulated more than 2,000 meters and has reached the bottom of yanjiang road in Hankou, about 500 meters away from the receiving well of Sanyang Road Station. The shield tunneling of the left tunnel has reached the underground of Hankou River Beach and is crossing the Yangtze River embankment. This means that both tunnels of Wuhan Metro Line 7 have been dug through the Yangtze River.