China’s largest Crossover TBM

The largest ever Crossover (XRE) TBM to be used in China launched in March 2021 in Guangzhou, the 9.16m (30ft) diameter Robbins TBM.

The TBM, which took five months from the start of assembly to machine launch, is being used by contractors Sichuan Jinshi Heavy Equipment Leasing Co., and CREC Bureau 2.

The hybrid machine is boring the 2.5km long Pazhou Line Lot PZH-1 of the Pearl River Delta Intercity Railway Project, which will offer better commutes for Guangzhou residents travelling to and from University City.

The machine will encounter various ground types during its bore, from moderately to strongly weathered argillaceous shales and sandstone to mixed face conditions. Much of the rock is fractured, while the quartz content is as high as 50%.

“Not only are there poor ground conditions such as soft to hard uneven, fractured zones and full-face hard rock, but these sections appear to alternate frequently, which is the biggest challenge of the project. It will be a test of performance and tunnelling efficiency for the machine,” said Yongsheng Qi, project manager for Robbins China.

The tunnel is also expected to cross under rivers and other bodies of water with a cover of 20 to 31m. The ground strata connects to the river and is highly permeable, resulting in expected water pressures above 7 bar. The project’s success lies in stabilising the water pressure at the face while ensuring acceptable advance rates and construction safety.

The Crossover TBM features both hard rock and EPB modes and is optimised for the rapidly changing ground found on the project. An adaptable cutterhead design and two-speed gear reducers known as the Robbins Torque-Shift system enable efficient tunnelling in hard, mixed, and soft ground.

The Pearl River Delta tunnel is scheduled to be completed by the end of 2021 and put into operation in 2023.