On 9th August I was lucky enough to be able to visit the worksite where the new Canary Wharf Crossrail Station is being constructed. The visit was organised by the London Branch of the Institution of Civil Engineers (ICE). The ICE was founded in 1818 to ensure professionalism in civil engineering. It represents 80,000 qualified and student civil engineers in the UK and across the globe.
Crossrail will run 118 km from Maidenhead and Heathrow in the west, through new twin-bore 21 km tunnels under central London to Shenfield and Abbey Wood in the east. It will bring an additional 1.5 million people within 45 minutes commuting distance of London’s key business districts. For more details of the route see the Railway pages on the Crossrail website or click the image below.
When Crossrail opens it will increase London’s rail-based transport network capacity by 10%, supporting regeneration across the capital, helping to secure London’s position as a world leading financial centre, and cutting journey times across the city.
Crossrail is being delivered by Crossrail Limited (CRL). CRL is a wholly owned subsidiary of Transport for London. Crossrail is jointly sponsored by the Department for Transport and Transport for London
Canary Wharf Station is on the South-East section of the route which spurs of the main Maidenhead to Shenfield line between the new stations at Whitechapel and Stratford and terminates at Abbey Wood. The station box is being constructed and designed on behalf of Crossrail by Canary Wharf Contractors Limited, a wholly owned subsidiary of Canary Wharf Group plc. It is being built for a fixed price of £500m, of which CWG is contributing £150m.
The station is being constructed by Expanded Group – a wholly owned subsidiary of Laing O’Rourke. The station box construction is a circa £100million subcontract. The works started in 2009 and are due for completion in Summer 2012 in readiness for the arrival of the Tunnel Boring Machines TBM’s. The TBM’s will bore into the complete station box, be ‘dragged’ through the box, and then continue boring out of the other end.
The station box is being constructed using ‘top-down’ techniques. In this method for the construction of deep basements construction starts at a commencing surface at or near ground level and works downwards by excavation and construction of floors until the base slab is reached. A common challenge in top down construction is the temporary support of the floor slabs as they are constructed – the permanent support to the floor slabs being via walls and columns constructed off the base slab once this is completed. The usual method for providing temporary support is via temporary steel ‘plunge’ columns cast into bearing piles constructed first from the commencing surface.
This basic methodology is being used to construct the station box at Canary Wharf. The station is however being constructed in an existing water filled dock and the commencing surface is actually around the dock floor level. Significant enabling works was required by way of a watertight cofferdam formed from tubular steel piles tied back to external anchor piles. A temporary access deck above the dock and ramp down into the cofferdam provides access to the commencing surface. The illustration below – taken from a project information board – gives an indication of the stages.
A selection of other Project Information Boards showing long sections through the works and some of the construction stages are included below. These open to large versions in new windows when clicked.
The works are easily viewable from public areas around the north side of Canary Wharf and I have visited and photographed a number of times over the past year when I have been at Canary Wharf on business or passing through. Photos from these visits can be found on my Google Picasaweb website and specifically as below:
Photos taken 5th October 2010
Photos taken 23rd November 2010
Photos taken 17th February 2011
Photos taken 29th June 2011
So. back to the visit organised by the ICE. I got up to Canary Wharf fairly early which allowed time for a spot of lunch and sight-seeing in Canary Wharf. A few of those photos here. I then took a look and some photos of the Crossrail site from the public areas as I have done previously. A selection of those photos are included below with more available on my Picasaweb website here. All photos open in new windows.
The site visit itself started with a very interesting presentation given by Expanded Engineer Andy Flynn. Andy talked through the Crossrail scheme and where the Canary Wharf Station sat within it before going on to talk in more detail about the innovative methods and teqniques that have been adopted on the scheme. I have to admit to being fairly familiar with the scope of the works at Canary Wharf – there being many similarities with another Crossrail main station structure that I recently worked on the bid for. I was still impressed with some of the finer detail of what had been done at Canary Wharf.
I liked for example the widespread use of pre-cast / pre-fabricated elements being used – a cornerstone of Laing O’Rourke’s construction ethos – such as precast concrete pre-stressed beams and precast wall and slab elements to reduce on site works. I was also taken with the tubular steel cofferdam structure that was externally tied to anchor piles that doubled up as supports for the suspended access deck over the dock water. I like too that the bottom half of the 100mm dia macalloy tie bars were attached to the anchor piles before driving to obviate the need for significant diving operations later.
I am hopeful of getting some further facts and figures about the works that I can include as I did not note them down in the presentation. In the meantime – in broad terms – the station box is around 260m long by 25m or so wide and from B3 level to base slab dig level it looks to be about 18m deep. This equates to around 120,000m3 or circa 250,000 tonnes of sands and clays that were excavated. The B3, B4 and B6 slabs are each around 6,500m2 and assuming the base slab is 1.8m thick this equates to 11,700m3 of concrete with around 3,000T of reinforcement (at 250kg/m3) in the base slab alone.
Following the presentation the group donned their obligatory Personal Protective Equipment (PPE), split into two groups, and headed out to see the works close up – and deep down.
At time of first publishing I have not had confirmation from the project team that I can publish any of the photographs that I took whilst on site. I have included below a photograph that is in the public domain of a view within the station box at the lowest level taken a few months ago. Click the picture to open – in new window- a blog by London based blogger and photographer Ian (@ianvisits on twitter) to read his blog on his recent visit with links to other photos he took on site. Rest assured that when I get approval I will update this blog to include my photographs.
Many thanks must go to ICE London Branch who organised the visit and to Expanded Group, Canary Wharf Contractors, and to Crossrail for allowing the visit to take place. The works going on at the Canary Wharf Crossrail worksite are a an exemplar of what can be achieved by civil engineers and a very visible demonstration of what civil engineers do.