New 5,291-ton tunnel machine spans 54.7 feet and can handle steep curves

China has rolled out its largest-diameter domestically developed shield tunneling machine, adding another massive piece of equipment to its efforts to build complex underwater and urban tunnels. The machine was completed in Zhengzhou, Henan Province in central China, on Tuesday. According to CCTV News, the machine has an excavation diameter of 54.7 feet, is about 410 feet long, and weighs around 5,291 US tons. It was jointly developed by China Railway Tunnel Group, China Railway No. 4 Engineering Group, and China Railway Engineering Equipment Group. Cutter head built for high-pressure work The machine uses a full-face constant-pressure cutter head, which lets workers replace cutters while keeping pressure steady inside the excavation chamber. This system works in high-pressure environments up to eight bars (about 116 psi). This feature helps reduce work stoppages and makes maintenance safer. Keeping pressure steady is especially important when tunnels go through areas with high water pressure. The equipment also uses a circulating slurry discharge system to remove excavated material. Its slurry treatment system uses an industry-leading “screw conveyor direct discharge + out-of-chamber crushing” approach. Slurry system reduces chamber repairs The system allows the slurry pump to discharge excavated material efficiently. The crusher is positioned outside the chamber, reducing the need for workers to enter the chamber for crusher repairs. This setup is meant to lower risks during underwater tunnel work. It also helps keep excavated material moving as the machine works through tough ground. The machine’s large diameter gives it a wide working area, and its design allows it to handle steep slopes and sharp curves. These situations need precise control of the machine’s position and direction during tunneling. Hydraulic supports help the machine turn Even though the machine is very large, it can make tight turns. Its propulsion system uses hydraulic supports that help adjust the machine as it moves through curves. A precise guidance system works with a segment selection system to control the machine’s position and where tunnel linings are placed. These systems allow operators to make small adjustments as the machine moves forward. This development shows China’s ongoing work on large shield machines for tough tunnel projects. In August, another very large slurry balance shield machine was finished in Hangzhou, Zhejiang Province, in eastern China. That machine is about 45 feet in diameter and 476 feet long, and it was built for high-speed railway construction. Yangtze tunnel reaches 351 feet deep One major project using China’s large shield tunneling technology is Nanjing’s first high-speed railway cross-river tunnel. The project stretches about 12.7 miles, with the tunnel section covering roughly 8.7 miles. The tunnel will run beneath the Yangtze River bed, reaching a maximum burial depth of about 351 feet. Water pressure can reach approximately 155 psi, making it the deepest and highest-pressure railway shield tunnel along the Yangtze River to date. Two slurry shield machines will excavate the passage from opposite ends. They are scheduled to meet with high precision and be disassembled on site about 98 feet below the floodplain on the river’s north bank. Get the latest in engineering, tech, space & science - delivered daily to your inbox.A versatile writer, Sujita has worked with Mashable Middle East and News Daily 24. When she isn't writing, you can find her glued to the latest web series and movies.