TBM u-turn and relaunch in Hong Kong 17 Aug 2017

Following successful completion of the first TBM drive on the twin tube Lung Shan Tunnel on the Liantang/Heung Yuen Wai Boundary Control Point highway project in Hong Kong, contractor Dragages Hong Kong has completed an underground u-turn and relaunch of the 14.1m diameter NFM shield for its parallel drive.

Map showing route of TBM drives and U-turn

First TBM breakthrough at Lung Shan road tunnel

The dual mode EPBM is the largest of its kind engaged in Hong Kong and the u-turn of the machine in a specially excavated cavern is another technical first in the region.

The first TBM southbound 2,400m long drive broke through in early March 2017. In the following months, the TBM was pulled into the 23m high x 27m wide x 40m long cavern that links to two tunnel alignments to turn 90 degrees to cross over to the parallel tube, and turn another 90 degrees into the relaunch position.

For the 90 degree turns, the TBM was lifted, rotated and shifted using solid ram jacks on a turntable that was first used by sister company Bouygues to turn the TBM on the twin tube Miami bored highway tunnel project in Florida, USA, in 2012.

Strand jacking was used for the longitudinal shift of the shield between the two tubes. Specialist heavy lifting subcontractor VSL was responsible for the design and operations of the sliding and jacking equipment. The four TBM backup gantries of 220 tonnes each were also turned in the cavern.

As the TBM was being turned and moved, other tasks were also underway. Among them, concurrent activities included:

• maintenance of the TBM, including refurbishment of the cutterhead after extensive wear on the first 2,400m drive, and repair of the articulation joint of the shield;
• preparations on the head wall for TBM break-in to start the parallel 2,400m long drive northwards; and,
• some adit and cross passage excavation.

Dragages Hong Kong launched the TBM on the first drive in late 2015 and from another specially excavated cavern of 200m long x 23m wide, which is claimed as the largest soft ground excavation span in Hong Kong. As it advances the 14.1m diameter machine erects a segmental lining of 2.2m wide x eight segments and a key in each 12.6m i.d. ring.

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  TBM on the turntable

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  TBM turned and moving towards second tunnel

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  TBM u-turn is a first in the region

Having turned into the second parallel heading, TBM excavation on the second 2,400m long drive through volcanic tuff began in June 2017 and is due to be completed in 2018.

U-turn completed at the second tube head wall

The TBM is equipped with several technical systems developed inhouse by Dragages, Bouygues and NFM. These include the Mobydic disc cutter monitoring system, the Telemach automated disc cutter replacement robot and the Roby 850 semi-automatic drilling robot.

Dragages Hong Kong is working on Contract No 2 of the Liantang/Heung Yuen Wai Boundary Control Point highway project, which is a transport cooperation project between Guangdong, Hong Kong and Macau. Work on the entire project for the Civil Engineering and Development Department (CEDD) of the Hong Kong Government, started in 2013, and will be the seventh land-based crossing between Hong Kong and Shenzhen. The supervising engineer on the project is AECOM and Atkins is the design consultant working with Dragages Hong Kong on the Contract No 2 with its Lung Shan Tunnel (Fig 1).

The 4.8km Lung Shan Tunnel will be the longest twin tube road tunnel in Hong Kong and is a combination of TBM and drill+blast excavation.