The construction of Crossrail’s Liverpool Street Station is being led by main contractor BBMV, a joint venture between ALPINE BeMo Tunnelling, Balfour Beatty, Morgan Sindall and VINCI Construction. RMD Kwikform, temporary works and engineering consultancy, has also provided a travelling formwork system to support the below-ground tunnel walls.
Positioned in a dense urban location in London, the construction works at this station became one of the most intricate and challenging projects along Crossrail’s high-speed link.
Due to the situation of the site, amongst one of central London’s leading financial centres, multiple factors had to be considered prior to work commencing. Not only are there constraints below ground level, which include existing tube lines and a network of sewers; the site above ground is surrounded by grade two listed buildings.
Andrew Chan, Shift team leader for BBMV, comments on the projects challenges:
“This project includes major construction and redevelopment works, both above and below ground. Due to the number of grade two listed buildings which encircle the entrance to our site at Finsbury Circus Gardens, contact grouting works had to be completed prior to any excavation works. This ensured that the ground would remain constant and at the correct level.
“We’re now working over 53-metres below ground and have excavated over 2km worth of tunnels. One of the key locations we’re working on is the core AP9 tunnel, this is the main connection between one of the escalator tunnels and the shaft, which connects to the station. We’re undertaking sprayed concrete lining methods to form the tunnel walls.”
Amongst the challenges already mentioned, the primary and most important challenge on any project, particularly of this magnitude, is safety. Incorporated in the AP9 section of the project is the C510 tunnel. Like other areas on the project, this tunnel has restricted access for operations; BBMV required a solution that would ensure complete structural support as they cast the secondary lining of concrete.
BBMV opted for a ‘traveller system’, which was designed by RMD Kwikform. It is positioned on castor wheels to support the curved, in-situ cast concrete tunnel and has provided an access platform and walk-way. With standard systems, once the concrete has been cast, the shutter is struck, dismantled and rebuilt to prepare for the next pour. However, due to the site constraints and cycle times required on this section of the project, a solution was engineered that allowed the site team to simply crack the shutter, and essentially ‘wheel’ the system along ready for the next concrete pour.
Peter Coppenhall, Morgan Sindall (BBMV) comments:
“Despite its complexities, the traveller is built of standard RMD Kwikform components that simply bolt together. Once we’ve got the shutter in place, we line the panels on top of the shutter. We’re able to jack these up and push everything into the desired position ready for the pour. Once everything is in place, we secure stop-ends which tie into the initial lining, and pump the concrete. After 12 to 15 hours, we crack the shutter and move everything along to be repeated.”
RMD Kwikform had previously worked with BBMV on Liverpool Street’s sister site, Whitechapel Station, where they provided a solution to support the headwall shutter.