Workers somehow managed to pour concrete into a void in an escalator machine room that broke through into the signal equipment room. With 30cm of rapidly-drying concrete on the floor, power and signalling had to be switched off for safety.
Main contractor Taylor Woodrow BAM Nuttall joint venture (TWBN) is building two new subterraneous ticket halls for Victoria tube station. The new southern ticket hall is adjacent to the existing Victoria Line one, close to the mainline railway station (pictured below). In effect, the old ticket hall is being doubled in size.
An all-new northern ticket hall is being built some distance away under Bressenden Place at the top of Victoria Street, connected by some 280m of new pedestrian link tunnels that are a significant part of the contract.
Under a £37m subcontract, ground engineering specialist Keller is improving the route of the tunnels. Through a series of 2,500 injections, it is jet grouting a solid tube of weak concrete that can then be safely excavated and lined to create a tunnel.
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Jet grouting involves drilling down, squirting a high-pressure water jet to flush out soil and then replacing that with cement grout. The cement grout injected under pressure mixes with surrounding material and hardens to provide solid ground that can be safely worked on. Keller started its ground improvement works back in November 2011 and is set for completion in May this year.
London Underground operations director Nigel Holness said: “Our contractors were working on the new station in an area next to the Victoria line signal control room. These works involved the use of water and cement, which leaked into the room, damaging equipment. This has meant there are no signals working on the southern section of the line.”
The line was shut all afternoon and evening but had reopened by Friday morning.
A full report on the Victoria Station Upgrade project can be seen in the January 2014 edition of The Construction Index magazine.
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