Five kilometers upstream of Jiangyin Yangtze River Bridge, a shield tunnel with the largest diameter of the Yangtze River at present is quietly crossing the river bottom. On December 25, the "Craftsmanship No. 1" shield machine had been pushed to the 1711 ring and driven to 3422 meters, 70% of which had already been driven, and it would soon cross the dike and go ashore. "Now we have started the most difficult tunneling section. The top of the cutter head of the shield machine starts to enter the silty clay layer, and the next 1000 meters of full section clay will be the biggest challenge for the shield machine." You Shaoqiang, 34, deputy project manager of China Railway 14th Bureau, said that we are confident to overcome the difficulties and continue to maintain stable and high production. Jiangyin Yangtze River Bridge, located between Jingjiang and Jiangyin, is the main passage of Beijing Shanghai Expressway across the Yangtze River and is known as the "throat" and "joint" of the Yangtze River Delta expressway network. The rolling traffic makes this area often "crowded", and the congestion often reaches tens of kilometers during festivals. In order to get through the "blocking points" and ease the traffic pressure across the river, Jiangsu Provincial Communications Engineering Construction Bureau led the construction of the Jingjiang Jiangyin River Crossing Tunnel. The tunnel is located at the bottom of the river for more than 50 meters, with a total length of 6445 meters. It is designed as a double hole, six lane tunnel. The outer diameter of the segment is 15.5 meters, and the excavation diameter of the shield machine is 16.09 meters. It is the largest diameter Yangtze River tunnel currently under construction in China. After it is completed and opened to traffic, it will drive through the river at a speed of 80 kilometers per hour, and the fastest time is only 6 minutes. On December 31, 2021, the "Jingxin No.1" shield machine with a total length of 165 meters and a total weight of 5100 tons will start tunneling. This is the first time that China has used the largest shield machine to cross the river. Along the way, you Shaoqiang's shield team overcame many difficulties with wisdom and courage. In the first three months, the team of You Shaoqiang worked nearly 12 hours a day, and even the Spring Festival was spent underground. In those three months, "Craftsmanship No. 1" only walked 16 meters. You Shaoqiang personally disclosed every segment and slurry pipeline. "Only when all the parameters are adjusted to the optimal state can the tunneling be safe and efficient." When the shield machine was driven to the 375 ring, the shield machine Changbai Xuan encountered an unprecedented problem. The shield machine entered the clay section, and the soil block, commonly known as "cement", tightly held the huge cutter head under the mixing of mud and water. The thrust reaches 190000 to 200000 kN, the torque reaches 16M Nm, the extrusion force exceeds 40000 kN, and the cutter head continuously heats up more than 50 ℃. After the experts' discussion, the project team found that the serious mud cake in the diversion tank was the problem, which could only be cleaned manually. At that time, the shield machine was more than 50 meters underground at the bottom of the river, and the front chamber pressure was more than 5 atmospheric pressures. Entering the chamber was risky and difficult. Each time the workers worked for an hour after pressurization, it took three hours to decompress when leaving the chamber. With extraordinary courage and insight, the project team, under the insistence of a service team composed of supervision, equipment, safety and medical care, entered the warehouse for 27 consecutive times in 4 days, and finally recovered to normal when driving to the 376th ring. Jiangyin Jingjiang Tunnel is a highway shield tunnel under construction with the highest water pressure in China. The ultra-high water pressure of 8.2 kg per square centimeter is another "threshold" for construction. When the shield machine crosses the river bottom, the shield shell, main drive and excavation silo must be designed and manufactured to withstand a pressure of 10kg. two thousand and twenty-two
Edit：wangwenting Responsible editor：xiaomai
Source：people.cn
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