A 14-meter-class ultra-large-diameter tunnel boring machine (TBM), Fenji, rolled off the production line on March 31 in Nantong City, East China’s Jiangsu Province. The machine, built by China Railway Construction Corporation Limited (CRCC), will be used in the Yangtze River tunnel section of the Yancheng-Yixing High-Speed Railway.
The Fenji tunnel boring machine rolls off the production line in Nantong City, East China’s Jiangsu Province. [Photo/sasac.gov.cn]
The 8,130-meter Yangtze River tunnel section of the Yancheng-Yixing High-Speed Railway connects the cities of Jingjiang and Jiangyin in Jiangsu. Designed as a single-bore, double-track tunnel, it supports a top speed of 250 kilometers per hour.
The TBM is expected to excavate 6,710 meters beneath the Yangtze River, passing through complex geological conditions, including soft soil, high-water-pressure strata, as well as sections with highly permeable sandy layers, bedrock protrusions, and gas-bearing formations. With a maximum burial depth of 71 meters and peak water pressure reaching 7.28 bar, the excavation will overcome multiple challenges, including the large cross-section, high water pressure, complicated terrain, long distance and the fragile environment.
The Fenji TBM is specially designed to excavate the Yangtze River tunnel. It is 145 meters long and weighs about 3,800 metric tons, with its diameter reaching 14.33 meters. The machine is equipped with multiple intelligent devices, which can operate with heightened precision beneath the river.
The machine can be remotely controlled and its key components are under real-time monitoring, advancing a fully integrated construction model featuring smart excavation, smart assembly, and efficient formation.
A China Railway 14th Bureau Group Corp worker tests the mud circulation system of the Fenji tunnel boring machine. [Photo/sasac.gov.cn]
CRCC adopts an innovative socket-and-spigot segment structure—an industry first in China—laying a solid foundation for intelligent assembly of the tunnel lining. The design of those segments was inspired by ancient China’s mortise-and-tenon joints, allowing the segments to be pushed into place in a single operation with tightly sealed joints. Compared with traditional segments, they have better performance in structural integrity and water-proofing.
The Fenji TBM is expected to increase installation efficiency and precision, owing to its high-precision, smart installation system.
The Fenji TBM will be dismantled and delivered to the construction site, where it will be reassembled and put into operation.
The Yancheng-Yixing High-Speed Railway connects the cities of Yancheng, Taizhou, Wuxi and Changzhou, as well as Yixing in Jiangsu. The 311-kilometer main line of the railway is under construction, along which there are 10 stations.
(Executive editor: Zuo Shihan)
