Author: J. Plant (Arup), S. Frost (Geada) and S. Roberts (AECOM)
2 July 2018
First published: 2 July 2018
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J. Plant (Arup), S. Frost (Geada) and S. Roberts (AECOM)
This paper describes the design carried out by the Arup Atkins Joint Venture (AAJV) under contract C134, principally of the Western Ticket Hall box. Nestled in Soho, this was developed within a dense urban grid and the constraints of a residential oversite development above.
The team worked closely with London Underground Ltd's engineers at the Eastern Entrance, which was delivered as part of London Underground’s own station upgrade works.
The tunnel for the eastbound Elizabeth line passes through the Western Ticket Hall box, which also provided construction access for the sprayed concrete-lined platform and concourse tunnels. Access dates to the site meant that there was insufficient time to complete construction of the box before the arrival of the tunnel boring machine (TBM). Consequently, the need to complete the excavation became critical and the team adopted a bottom-up construction sequence for one of the deepest open shafts ever excavated in central London. The box, formed of elements of diaphragm walls and raft, was constructed before the TBM arrived, and the remaining internal elements completed afterwards.
The new Elizabeth line station at Custom House was a unique opportunity for design and construction. It is the only above-ground station on the central section of the line and will welcome millions of visitors to London’s largest conference centre, ExCeL, as well as providing vital connections for the Borough of Newham. A joint team from Crossrail Ltd, Atkins, Arup, Allies & Morrison, and Laing O'Rourke collaborated to develop the striking station design, creating a beacon for both the Elizabeth line and the local community. Faced with many constraints, a ‘kit of parts’ strategy was developed for Custom House’s construction, including prefabricated and standardised components. This approach – where much of the station was built off site – minimised workon site, drove down programme times and costs, and reduced the impact on the local community. The approach also led to Custom House’s excellent health and safety record – one of the best of any Elizabeth line station to date.
Canary Wharf was the first station on the Elizabeth line to be constructed, and the first to be let as a design-and-build contract, with developer Canary Wharf Group. Innovative design and construction techniques enabled the station box to be completed four months ahead of the development programme. Construction of the Crossrail Place retail and leisure oversite development (OSD) proceeded concurrently with that of station. The OSD included a number of features aimed at increasing future flexibility for the developer and tenants. A timber gridshell roof completes the development, partially covering a large roof garden that is open to the public. The OSD opened in May 2015, nearly four years ahead of the planned station opening.
There is something special about megaprojects that brings out the best in engineering design and construction. It could be that the longer-term durations for the planning, design and build phases allow more measured and thoughtful decision making; it could be that the weight of public exposure and expectation creates an added incentive to succeed; it could be that the prestige of being part of the programme attracts the best teams in the best organisations; it could be that the extended schedule nurtures a team spirit and a collaborative way of working that is difficult to achieve in a typical shorter-term project.