The Beijing East Sixth Ring Road Reconstruction Project reports that its slurry TBM, ‘Jinghua’ has reached an intermediate shaft, breaking through in September 2022, 16 months after it was launched. The machine had to mine the first 4.8km section of the drive beneath urban areas and through challenging geology without stopping for cutter changes.
The 16km-long ring road project is an essential part of Beijing’s masterplan, designed to relieve congestion on the East Sixth Ring Road and stimulate the development of the Beijing-Tianjin-Hebei region. The tunnel is 7.3km long.
Manufactured by China Railway Construction Heavy Industry Corporation (CRCHI), and with an excavation diameter of 16.07m, this slurry TBM is the largest machine of its kind to have been made in China. The 4,300-tonne, 150m-long machine has a series of design features aimed to optimize its operation.
These features include fourth-generation accessible cutter change technology, a telescopic main drive, extremely high pressure auto-compensation, large power slurry circulation system, and synchronous two-component grouting. The successful application of the synchronous grouting system has allowed the control of ground settlement to within millimetres, according to CRCHI, which has ensured existing buildings have not been disturbed during the TBM drive.
The geology along the length of the tunnel is mainly sandy soil, water-rich and high-density sand, interactive layers of silt and cohesive soil. Technical challenges have included low initial cover and long distances tunnelling through high-density sand layers. The TBM bored continuously beneath the Beijing-Harbin Railway and a major transportation hub without disturbing the existing infrastructure. Its record production rate was 542m in one month.
Following maintenance and inspection in the ventilation shaft, Jinghua will excavate the second section of the tunnel, finishing its drive at the reception shaft in Wansheng South Street.