The "longest subway loop in Asia" in Wuhan has safely crossed the Yangtze River levee

On the evening of May 15, Wuhan Metro Line 12, the longest subway loop in Asia, received another good news. In the crossing section from Kpu Park Station to Danchi Station, the shield machine "Jiangcheng Excellence" successfully reached the 500th ring and successfully broke through 1,000 meters, safely realizing two first-class risk sources, namely the starting of the shield machine and the crossing of the Yangtze River levee. In the next step, the shield tunneling machine will enter the mudstone layer of the whole section, which is also the most difficult underriver crossing.

According to the introduction, the section between Koppu Park station and Danchi Station is located in the lower reaches of the Erqi Yangtze River Bridge. The tunnel is 4,012 meters long and 2,160 meters wide, making it the longest subway tunnel across the Yangtze River in China. With a total length of 121 meters and a total weight of 2,963 tons, Jiangcheng Excellence shield Machine has an excavation diameter of 12.55 meters, equivalent to the height of a 4-story building. Since its inception, the Jiangcheng Excellence shield machine has wielded 22 sets of hydraulic jacks and exerted 15,000 tons of thrust, driving at an average speed of 6 meters per day.

Dong Jiaqi, the operator of the shield machine, skillfully operated the buttons on the panel in the control room of the shield machine of Excellence on the evening of June 15. He introduced that the equipment of the shield machine is very precise, and each monitoring data is calibrated in the smallest unit such as millimeter. According to the soil pressure and bulk density of the stratum, it is judged that the longitudinal and transverse forces of the shield machine should be given to ensure the uniform tunneling forward of the shield, not only to avoid the settlement of the tunnel, but also to ensure that the tunnel does not leak.

According to reports, the shield machine is soft and hard on the ground, above is fine sand, below is silty mudstone, great wear to the tool, so far has changed the tool more than 20 times, more than 300. In the next step, the shield tunneling machine will enter the most difficult mudstone layer up to 400 meters, with an average strength of 30 mpa, which is easy to form mud cake during tunneling and accelerate tool wear. In response, they use the DCRM system to accurately detect tool wear, tool rotation or abnormal temperature, and prompt replacement of tools. In the face of the whole section of mudstone layer, Dong Jiaqi said that he had found a good way: "push the shield machine forward for a while, and then idling for a while, at the same time with high pressure water to wash the cutter, the mud cake washed away and then forward digging."

According to reports, Dong Jiaqi has participated in the construction of Hangzhou Wang Crossing River channel, the geological analysis, slag sample analysis, tool monitoring and sound acquisition information can be accurate analysis, such as his young "old workers", accounting for 50 percent of the construction team across the river shield, has become the new force of the shield.

According to the introduction, Line 12 is the first circular subway line in Wuhan, with a total length of 59.9 kilometers and 37 stations. The line crosses the Yangtze River twice and the Han River once. After the line is completed and opened to traffic, it will effectively relieve the passenger flow pressure in the central urban area and realize the "three towns in the same ring", which is of great significance to accelerate the key urban development and improve the urban comprehensive transportation system.