Herrenknecht has delivered a Mixshield tunnel boring machine (TBM) for the construction of a 3.3km two-storey road tunnel with three lanes in both directions in the eastern Chinese city of Jinan.
The Mixshield technology is designed for the extreme conditions of tunnelling under the Yellow River. The TBM is currently being dismantled and then reassembled on the construction site.
The order for the Herrenknecht’s Chinese subsidiary Herrenknecht Tunnelling Machinery (HTM) was for a machine to cross under the Yellow River in Jinan, in a geological environment with high groundwater pressure, and to create just one tunnel tube for both directions of travel.
A correspondingly large diameter was therefore required: 17.5 metres.
A machine of this diameter has only been used twice before in the history of tunnelling – the largest in 2015 in Hong Kong, which was also a Herrenknecht Mixshield, with a diameter of 17.63 meters).
By comparison, Crossrail (Elizabeth Line) TBMs were around seven metres diameter and the biggest HS2 machines are around 10 metres.
To adapt to the clay, sand and silt geology and the 7.5 bar groundwater pressure under the Yellow River, a Mixshield TBM was selected. Herrenknecht’s Mixshield technology is an advance on conventional slurry technology: the support pressure in the excavation chamber is managed using an automatically controlled air cushion. This means that heterogeneous geologies and high water pressures of more than 15 bar can be controlled even with very large excavation diameters. An individual, new slurry circuit was designed especially for this TBM, which has been called Shanhe.
The TBM’s 5,600 kW cutterhead drive delivers 35,017 kNm of torque
Jinan, 400 kilometres south of Beijing, has a population of nine million and is the capital of the Chinese province of Shandong. The Jinan Huanggang Road Yellow River Crossing Tunnel is already the second road tunnel project to cross under the Yellow River in 2024. Tunnelling is scheduled to begin in late 2024.
The contractor is China Railway 14th Bureau Group Company and its client is Jinan Urban Construction Group.
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