The 12.61m-diameter mixshield TBM, operated by the China Railway 14th Bureau project team, excavated 11.94km.
Herrenknecht, which supplied the machine, said there were multiple challenges during tunnelling, including high water pressure, complex geology, and buildings in Chongqing.
The tunnel passes through a mountain comprising karst, a fracture zone, a coal seam gas area, and goaf, and crosses the Yuzhong Peninsula and the South Bank area.
Where it passes under the approximately 42m-deep main channel of the Yangtze River, the tunnel has a minimum overburden of about 10m, and a maximum water pressure of 9 bar. Water penetration along this stretch was also a challenge.
The TBM was customised with a series of advanced solutions including a high-precision gas-hydraulic pressure balance system, high-pressure scouring system, and high-wear resistant tools. Automatic monitoring of harmful gases and automatic balancing of main drive seal pressure were also successfully introduced.
The Chongqing-Xiamen high-speed railway will cut the travel time from Chongqing’s Qianjiang River to the main urban area of Chengdu-Chongqing from four hours to less than one hour. Some sections of the new line are already in operation.
