Tunnel boring machine (TBM) manufacturing giant Herrenknecht this week fought off competition to win contracts for all six earth pressure balance (EPB) machines required to bore Crossrail’s 21km long running tunnels.
No UK competition
Herrenknecht had been a front runner for the work and faced no competition from the UK supply chain as there are no TBM-manufacturers based here.
The company was last seen in the UK when two of its machines dug the twin bore tunnel beneath the Thames for High Speed 1 (HS1), providing it with experience of the tricky ground conditions under the capital.
Crossrail contractors for each of the tunnelled sections − Bam Nuttall/Ferrovial/Kier in the west and Dragados/John Sisk in the east − both selected the manufacturer for their work.
NCE understands that the maximum figure expected to be paid for each of the machines is £15M.
The German firm is well known in the UK for its EPB and slurry TBMs but also used two of its Mixshield machines − capable of dealing with changeable ground conditions − for the HS1 tunnels, where the excavation went through alluvium, chalk and flint beneath the River Thames.
The EPBs for Crossrail will pass through ground that is predominantly London clay, sand and gravels.
All go for 2012
Herrenknecht will deliver two TBMs to the Royal Oak portal for the western running tunnels to Farringdon in early 2012, two TBMs to Limmo Peninsula for the eastern running tunnels to Farringdon in mid-2012 and a further two machines to Stepney Green later in 2012 going eastward to the Pudding Mill Lane portal, meaning that the build process for the machines is expected to get underway shortly. The first launch is expected at Royal Oak in spring 2012.
As the Thames Tunnel construction contract has only recently been awarded (NCE 14 April), the TBM manufacturer for this tunnel drive will not be announced until later this year. Herrenknecht is likely to remain in the running to provide the final TBM − a slurry machine − for this final tunnel drive at the Thames Tunnel, which is in chalky ground.
Consideration is also now being given to the need for a further TBM on the short drive between Limmo Peninsula and Victoria Dock Portal.
“These monsters of the deep will create the tunnels that will make it easier for millions of people to whizz east to west across our city.”
London mayor Boris Johnson
Crossrail said the method of constructing this tunnel section is “the subject of ongoing discussions with the tunnelling contractor”.
The TBMs required for Crossrail will be up to 120m in length and weigh around 850t. Herrenknecht’s six TBMs will be transported to London by boat from the its factory in Schwanau, Germany.
Specific points of arrival in the UK have yet to be agreed between the manufacturer and the tunnelling contractors. Before they depart for the UK the machines will be fully assembled and tested before being dismantled into sections ready for transport. Cutter heads for the TBMs will arrive in sections and will be transported to the tunnel launch sites before assembly.
“There is nothing boring about the leviathan machines that will soon be burrowing their way through the earth way below our streets,” said London mayor Boris Johnson. “These monsters of the deep will create the tunnels that will make it easier for millions of people to whizz east to west across our city.”
24 hours, 365 days schedule
The tunnelling schedule is tight with the TBMs planned to run nearly 24 hours a day, seven days a week, 365 days a year. Scheduled breaks will allow TBM maintenance to take place and tunnelling activity will stop for certain public holidays including Christmas Day.
Each TBM will be operated by a “tunnel gang” comprising around 20 people − 12 on the TBM itself and eight people working from the rear of the machine to above ground.
Crossrail has also confirmed that the concrete segments for the western running tunnels between Royal Oak and Farringdon will be manufactured at Old Oak Common and transported to the TBM by rail.