Eight TBMs have been ordered by the four contractor joint ventures (JVs) for the construction of 20km of twin tube tunnels worth $860M on the UK’s Channel Tunnel Rail Link (CTRL) Section 2.
Firstly the Nishimatsu/ Cementation Skanska JV has ordered two 8.1m diameter Kawasaki dual mode TBMs to bore the $205M, 7.5km long contract 220 section from the Stratford Box to the London West Portal at Kings Cross/St Pancras. The machine’s key components will be manufactured in Japan with the majority of the remaining manufacture being undertaken in the UK. Markham of Sheffield has been awarded the fabrication contract whilst assembly goes to Qualter Hall in Barnsley. Delivery schedule details were unavailable as T&TI went to press.
Contract 240 JV Costain/Bachy Soletanche will construct the 4.7km long, $168M tunnel section from the Stratford Box to Barrington Road using two 8.1m diameter Wirth EPBMs. The machine’s shields will be a bolted segmental design with sacrificial skins to enable dismantling within the tunnel upon drive completion. Lining will be segmental using a vacuum pad reducing the id to 7.1m. The tunnel passes through dewatered Thanet Sands. Spoil will be conveyed from the cutterhead muck chamber through a 900mm diameter screw onto a conveyor out of the tunnel.
The first TBM will be delivered to site at the start of July 2002 with the second following in August 2002.
Lovat of Canada has scooped the award to supply two machines with backups to the Edmund Nuttall/Wayss & Freytag/Kier JV for construction of Contract 250 Barrington Road to Ripple Lane. The $161M section includes 5.3km of twin tube tunnels.
The machines are both 8.1m diameter mixed face configuration designs, convertible from EPB to open mode. The TBMs will install a lining of 10 pre cast concrete segments (including the key) using a vacuum-type erector with continuous grouting through ports in the tail shield. The first TBM is due to arrive on site in June 2002 for commencement of driving in August 2002. The second will arrive a month later in July and begin boring in October.
JV Hochtief/Murphy has chosen two Herrenknecht Mixshield machines to construct the 2.5km bored section under the River Thames on the $180M Contract 320. Both TBMs will have an 8.1m diameter with the cutterheads being equipped with roller cutters for hard material and picks for the softer chalk. Spoil material will be transferred to surface via a 350mm slurry pipeline. An internal crusher will reduce anticipated flints to a nominal size of 150mm. The machines will also incorporate two man-locks to allow head maintenance and inspection.
The first TBM will arrive on site at the beginning of May 2002 with the second following in January 2003.
The $7.3bn CTRL scheme when finished will halve journey times between the Channel Tunnel and central London and is seen as vital in the UK’s inclusion in the European High Speed Network.
Related Files
Map showing the alignment and tunnel contract division of the CTRL 2 route from London to Kent.
