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Paving the way through London’s soft core Conveyor drives for rapid transit tunnel construction in central London
German technology for new train lines in London: the tunnel boring machines supplied by Herrenknecht.
T
he metropolis London is currently adding a new East-West rapid transit connection with a length of more than 100 km to its much-frequented public transport network.
For this major project, 21 km of new tunnels are being bored in the city center alone. The soil here mainly consists of soft clay with a sticky consistency that makes the transport of excavated material especially challenging. H+E Logistik and NORD DRIVESYSTEMS, two German industry specialists, are supplying suitable conveying technology including geared motors. Named after the mathematician Ada Lovelace and the city map pioneer Phyllis Pearsall, Ada and Phyllis are tunnel boring machines (TBMs) from German manufacturer Herrenknecht, each measuring approximately 100 m in length and weighing about 1,000 tons. Working for the rapid transit project “London Crossrail”, they have been pushing forward their 7 m wide “Cutterhead” blades below the City since 2012. After tackling the distance of six and a half kilometers between Royal Oak and Farringdon Station, they are planned to resurface in 2015. Besides Ada and Phyllis, more TBMs are currently boring similar tunnels in various other track sections for the
01 | Magazine Industry USA | November 2013
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East-West connection through London which will measure a total of 118 km. The first Crossrail sections will be put into operation in 2018. With an investment volume of more than 17 billion EUR, “London Crossrail” is currently Europe’s largest infrastructure project. Demanding transportation task The TBMs excavate up to 1,300 tons of “London clay” per hour in the two 6.2 m diameter tunnels that are being bored in parallel below the city center. The handling of this soft material does require solutions that are tailored to its consistency. In this case, the challenge lies in reliably transporting the excavated material away from the building site, which includes routing it over machine, tunnel, and hall conveyors before loading it onto trains. State-of-the-art tunneling includes the addition of tensides to the excavated material directly at the boring machines in order to facilitate handling. However, if the special London clay formation and these additives came into contact with standard conveyors, complications would soon arise: the mass would promptly and persistently stick to parts of the conveyor belts. Tunnel conveyors for the “London Crossrail” project were