Have you ever wondered what is happening below ground in the City of London?
Below the redevelopment of Grade II listed Smithfield Market and the New Museum of London is the subterranean Snow Hill Rail Line.
Our specialist rail division worked in the Snow Hill tunnel to provide protection scaffold. Ensuring that no debris would fall on the track and cause delays to the trains between Farringdon and City Thameslink stations. Above ground, Smithfield Market is being redeveloped to home the New Museum of London. The ground needed to be excavated and in doing so there was a risk of damaging the Victorian brick arches which could result in debris falling on the lines below. Protection scaffold was required to eliminate this risk.
The history of the tunnel below the iconic market is rich. Smithfield Sidings have been used for many years for a variety of reasons, from freight purposes to enabling trains to terminate short of the end of an underground line. This reduced the number of lightly loaded trains running all the way to the final station.
Being part of this project with Kier Utilities and Rail provided us with some unique challenges to overcome, which required equally unique solutions.
The initial area of work was to build the protection scaffold to the Smithfield Sidings. We installed a conventional bridged crash deck to the underside of the tunnel roof, which consisted of 3 support scaffolds, one at either side and one in the middle of the tunnel.
The second phase of work was on the railway arches which provided more of a challenge due to overhead cables. Scaffold was erected above the cables and within the tunnel arches ensuring adequate clearance above the active lines.
The crash deck was suspended from the tunnel walls at high level. This ensured that there was enough room for train clearance. However, we found that large areas of the tunnel walls were in poor condition with years of water ingress, making the bricks unsuitable for tying.
The extensive design process enabled us to overcome this challenge and several tie tests were carried out to find a solution that would support the imposed loadings.
Aluma beams were used for the crash decks as they were able to fit between the railway arches and overhead cables. Additionally, they were the only beams that would be able to take the imposed loadings.
Working above an active train line meant that working hours were largely restricted. Works were only permitted to be carried out during 27 hour possessions. These possessions required considerable planning with a team of over 100 operatives and supervisors.
Once complete, our works allowed for the excavation of the ground floor level above, down to the existing arch level. A new floor slab could then be laid to form the base for the new Museum of London.