Mega slurry TBM ready for Chunfeng project 11 Oct 2018

CREG News Release

CREG is celebrating the successful factory testing of its 15.8m slurry TBM for the Chunfeng highway project.

15.8m mega slurry TBM ready for dispatch to the Shenzhen city
15.8m mega slurry TBM ready for dispatch to the Shenzhen city
The large diameter will accommodate a four-lane double-decked highway
The large diameter will accommodate a four-lane double-decked highway

The large machine will now be disassembled in at the Zhengzhou factory and prepared for dispatch to the project in Shenzhen City where it will be assembled and launched for its drive under the Jibu River in early 2019.

The TBM will bore a tunnel of 3,483m as part of the 5km highway project with a awarded to the China Railway Tunnel Group (CRTG).

The tunnel overburden ranges from 23m-62m while the maximum gradient is 49%. The anticipated geology consists of mainly granite to a maximum 173.7 MPa in unconfined compressive strength, metamorphic sandstone, tuffaceous sandstone and moderately weathered schist.

To work with a TBM of this scale, there are a number of major technical risks that need to be managed effectively. The TBM will cross 11 fault zones of up to 431m wide and will negotiate a minimum curve radius of 750m.

To ensure the smooth excavation of the giant machine, CREG has adopted a series of innovative approaches during the design phase. In order to maintain safe excavation at 8 bar pressure and keep water tightness, CREG built a specialised high-pressure sustaining system into the machine.

The presence of numerous rock types poses great challenges for cutting efficiency and cutter wear. To cope with this, twin crushers have been used to ensure efficient cutting and to lower the chance of slurry chamber clogging at the same time. In addition to that, an online system is applied to the machine for real-time monitoring of cutter wear. Due to the machine’s size more maintenance is needed. Considering the high risk of pressurised cutter intervention, CREG has developed a customised main drive capable of telescopic movement and swinging in all directions to allow changing cutting tools under atmospheric pressure. Another point of concern for this project is the settlement control as the tunnel goes underneath a residential area, the city’s Metro Line 9 and other urban buildings and public infrastructure. To mitigate the risk, CREG came up with four circuit lines of air pressure control for the machine to minimise the settlement during operation.

CREG celebrates the successful testing of its 15.8m TBM
CREG celebrates the successful testing of its 15.8m TBM

The completed tunnel will be an expressway for cars. It will be the first single-bore with double-decked interior which will provide four lanes and two continuous emergency parking lanes, three in each tube in Shenzhen. Traffic on the two decks of each tube will run in opposite directions. Besides the underground part, the overall Chunfeng Tunnel Project also includes reconstruction to link the tunnel portals to the current road above ground. The project is a major part of the Shenzhen Municipal Government’s bid to ease the congestion of the existing Chunfeng Viaduct due to the present unmatched lanes. With the completion of the underground tunnel, traffic should be significantly reduced.

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