World's largest-diameter high-speed rail shield machine "Navigator" successfully breaks out of tunnel

Recently, construction is in full swing on the Chongtai Yangtze River Tunnel, a landmark component of the Yangtze River High-Speed Railway, a key national project under the 15th Five-Year Plan. Buried 89 meters beneath the Yangtze River bed, the Navigator, the world's largest-diameter shield machine for high-speed rail tunnels, has finished excavating the 11.18-kilometre underwater section of the tunnel and safely reached the southern bank, advancing steadily toward the final receiving shaft.

Giant National Equipment Setting World Records

Stretching 14.25 kilometres in total, the Chongtai Yangtze River Tunnel serves as a critical control project on the Shanghai-Chongqing-Chengdu High-Speed Railway and ranks as the world's cross-river high-speed rail tunnel boasting the strictest construction standards, longest single driving distance and largest overall scale. Launched from Chongming Island of Shanghai in April 2024, the Navigator shield machine has worked for 23 months and notched multiple world records:

■it is the world's first 15-metre-class large-diameter shield to complete a single continuous excavation of 11,182 metres.

■it bored through the Yangtze River at a maximum overburden depth of 89 metres below the riverbed, with a peak monthly advance of 718 metres, leading global construction efficiency.

■designed for a top operating speed of 350km/h, the tunnel pioneers non-speed-reduction river crossing for high-speed railways worldwide.

Extreme Challenges, Proven Superior Strength

Custom-built exclusively for the Chongtai Yangtze River Tunnel, the Navigator shield machine is well-deservedly hailed as an "underground aircraft carrier":

■key specifications: Cutterhead excavation diameter of 15.4m, overall length of roughly 148m and total weight of approximately 4,000 tonnes.

■intelligent control core: Equipped with an intelligent control system, it enables manned-on-duty and unattended automatic construction. The machine can independently conduct perception, data analysis and operational decision-making to achieve precise tunnelling deviation correction.

■eco-friendly construction: Adopting slurry separation and wastewater recycling technologies, it ensures zero spillage of slurry and muck to protect the ecological environment of the Yangtze River.

At present, Chinese shield machines hold a 70% global market share, with products exported to more than 40 countries and regions across five continents. During the 14th Five-Year Plan period, China achieved leapfrog development in ultra-large-diameter shield machines with a diameter of 14 metres and above.

▲The Qiming, the world's largest-diameter shaft boring machine (SBM), features a double-arm structure integrating excavation, muck removal and guiding functions. Capable of large-cross-section and ultra-deep underwater excavation, it is deployed for the No.2 shaft of the Chongtai Yangtze River Tunnel.

During the 15th Five-Year Plan period, CRHIC will unswervingly follow the development path featuring high-end development, digital & intelligent transformation, green development, integrated innovation and international expansion. We will keep ramping up efforts on larger excavation diameters, higher construction efficiency, ultra-deep strata operation and diversified application scenarios to facilitate the delivery of more mega-projects worldwide.