Milly the Muncher Cruncher began her 2.5km long journey under the Thames on 11 July, signalling the start of tunnelling on Section 2 of the UK’s Channel Tunnel Rail Link (CTRL) under London.
The Hochtief/Murphy JV is operating the 8.16m diameter Herrenknecht full-face slurry TBM (pictured left) on the US$203M contract 320 between Swanscombe, N. Kent and West Thurrock, S. Essex. Milly is scheduled to bore 85m per week, encountering alluvium, terrace gravels and chalk, placing 33,000 concrete rings. The fully pressurised head is designed to withstand the 4.5 bar expected at the maximum 40m tunnelling depth.
When the ‘down line’ tunnel is completed after eight months, the backup will be dragged back through the tunnel over four weeks to Swanscombe where it will be fitted with a new Herrenknecht shield for the ‘up line’ London bound tunnel.
Contract manager, Tony Bermingham, said this was the preferred method because money spent on a brand new machine will be money saved in time. “We are on a tight schedule. If you take the machine apart, carry it back over the bridge – which has a strict weight limit – refurbish it then put it all back together again, it takes time, and it’s time we don’t have.”
Herrenknecht will take back both machines in a buy-back clause.
The 280,000 cubic metres of spoil from the tunnel, once filtered, will be deposited in a nearby disused quarry, in preparation for a new housing estate.
Meanwhile, one of the two Wirth EPBMs ordered by the Costain/Skanska (UK) Ltd/Bachy Soletanche JV (pictured right) is ready and will soon be on its way to the contract 240 site in Stratford. Construction on the twin bore 4.7km, 7.15m i.d. tunnels to Barrington Road, Newham, is due to start in September 2002.
The US$8.1bn CTRL project is on target and within budget. Civil engineering on Section 2, between Southfleet in North Kent and St Pancras station in Central London, began in July 2001 and is 22% complete, and Section 1 between the Channel Tunnel and Fawkham Junction in North Kent is 89% complete. The full link should be completed by 2007.
