Main contractor VINCI Construction UK Limited has been awarded the contract for the refurbishment of the Connaught Tunnel.
With a history that dates back to 1878, the Connaught Tunnel allowed the railway to be diverted under the Connaught Passage, a water link which connected the Royal Victoria Dock and Royal Albert Dock. The tunnel came under the spotlight in 2008, when it was featured in Guy Ritchie’s film ‘RocknRolla’.
Unfortunately, the central sections of the Connaught Tunnel became weaker after the Royal Victoria Dock was deepened in 1935 in order to allow larger ships to enter the dock. As part of the works, the central section of the Connaught Tunnel was narrowed, the brickwork was removed and cast iron segments were installed. This resulted in the roof of the Connaught Tunnel below the dock being exposed.
The prestigious project will include enlarging the existing tunnel so that it can accommodate Crossrail trains and overhead line equipment. As sections of the existing tunnel are in poor structural condition, approximately 100m of tunnel wall will be removed and replaced with a new tunnel lining. In addition, the existing brick arches and part of the tunnel approaches will be retained and repaired.
Crossroads Project Manager, Linda Miller, said: “In 20 years of digging tunnels, this is the most fun and fantastic opportunity. It presents all sorts of problems but that’s what I love.
“There are some beautiful arches and the original plan was to take them away, to cut them out and to replace them with the modern equivalent but I’m happy to say that a decision was taken by Crossrail to preserve them and clean them up to bring them back to the way they looked 150 years ago.”
One of the first phases of work to be carried out is the reinforcement of the central section of the Connaught Tunnel, which lies at the bottom of the Royal Victoria Dock at the border with the Royal Albert Dock.
The reinforcement stage will include the installation of a large concrete base, which will in turn ensure the safety and stability of the tunnel. A wide passageway will be dredged between the Royal Albert Dock and Royal Victoria Dock and then a 1m thick reinforced concrete protection slab (measuring 100m³) will be installed on the bed of the passageway, which is located just west of the Connaught Road Bridge. This slab will be placed using marine pontoons and a team of specialist divers.
Following this phase, the cast iron linings in the Connaught Tunnel will be removed in stages. In order to ensure the integrity of the existing tunnel, the remainder of the brick-lined tunnel will be grouted and filled with a low strength foam concrete. These tunnels will subsequently be enlarged by boring through the foam to create binocular tunnels which are large enough to allow Crossrail trains to pass. Precast concrete tunnel segments will then be installed in this section of the tunnel.
Piling and concrete works to construct the track slab at the west end are expected to be completed in July 2012, followed by the same process at the east end. The refurbishment of the tunnel itself will commence after July 2012 and is expected to be completed in October 2013.
Abwood Contract Support Ltd
Since it was established in 1997, Abwood Contract Support Ltd has been a leading specialist in marine and underwater engineering & construction, term maintenance and diving services.
Abwood provide services across London and the South East, whilst their extensive wealth of experience has been required nationally and in places as far away as the Middle East.
The company has been involved in two Crossrail projects. For the Canary Wharf project, Abwood surveyed the proposed cofferdam’s pile line for obstructions and then assisted the contractors with the removal of the obstructions. They were also involved with tying in the cofferdam with listed heritage dock walls, the installation of an underwater concrete base slab prior to the drain down of the cofferdam and various other tasks throughout the marine construction phase.
For the Connaught Tunnel project, Abwood carried out an initial survey of the walls and dock bed of the dock passage above the tunnel. They then returned to remove the dock sediment and debris from the dock slab, in order to facilitate a detailed bed and wall survey for the client.
Drew Allan, Abwood Contract Support Ltd, said:
“In addition to works on the Olympics project, we are fortunate enough to be involved with two of the main construction projects in London at the moment. We are delighted to be working on this project, both with VINCI and all of the relevant site and management teams.”