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The Barbican Arts Centre is the centrepiece of the Corporation of London’s redevelopment of the area. Housing a 2000-seat concert hall, theatre, cinema and music and dance school, it is a cultural hub for this part of the city. It was, however, the last major element of the Barbican scheme, which already included two residential tower blocks. With much of the Arts Centre being underground, we had to solve the complex problem of forming its substructure without compromising the foundations of these surrounding buildings.
As plans for the Arts Centre evolved, so too did its size, increasing with each iteration. The final form of the building would need us to design and construct an enormous excavation right next to the towers, removing a staggering 190,000m2.
Project Summary
20 acres floor area
190,000m2of excavated London clay
Clay: a major design challenge
• The greatest challenge to the Barbican Arts Centre is one that cannot be seen. London clay. With its propensity to swell and shrink, it poses a very particular set of challenges.
• The Arts Centre would sit right next to the Barbican’s residential towers. The Cromwell Tower is 43 floors high and, at 44 floors, the Shakespeare Tower was for many years Europe’s tallest residential building. The new foundation works would have to avoid influencing these structures, as well as the underground railway running under the site.
Moving 190,000m2 of soil without moving foundations
London clay has become a familiar foe to our geotechnical teams. Many of our projects in the capital stand on clay. We had earlier designed the foundations for the two Barbican towers, giving us an intimate knowledge of the site and its soil conditions. The permeability of London clay would lead to differences in pressure against the Centre’s retaining walls. To overcome this, our team opted to preload the substructure system using flat jacks. That way, once the forces in the props were raised, the huge quantity of soil could be safely removed, creating the void for the theatre and allowing the construction of the foundation slab to begin. Carried out in September 1974, the jacking took just two days to complete.
The team monitoring the Cromwell and Shakespeare Towers during the jacking and excavations did not detect any material difference to the level or inclination of the two blocks. When considering the sheer volume of the excavation, that is a testament to the precision of the team’s calculations.
Shaping a better world
Founded by Sir Ove Arup, we are firm of designers, planners, engineers, architects, consultants and technical specialists all focused – like our work at 52 Lime Street – on shaping a better world.