Comparison Between Sprayed and Cast In-Situ Concrete Secondary Linings at Bond Street and Farringdon Stations

Summary

A joint venture of BAM, Ferrovial and Kier (BFK) have constructed the station tunnels at both Bond Street and Farringdon Stations, as part of Crossrail contracts C410 and C435 respectively. These tunnels were all excavated and supported with a sprayed concrete primary lining.

The secondary linings at Bond Street and Farringdon were constructed using different methods. Bond Street had a sprayed waterproofing membrane, a sprayed steel fibre reinforced concrete layer and a smoothing layer containing polypropylene fibres for fire resistance. In contrast, Farringdon had a sheet waterproofing membrane and a single layer of cast in situ concrete containing both steel and polypropylene fibres. Farringdon Station was the only contract on Crossrail to have a fully cast tunnel lining in the platforms, and therefore BFK have a unique perspective to compare the relative merits of the two secondary lining systems.

There is a trend in the UK industry towards sprayed secondary linings over cast in situ. This paper presents a direct comparison between these two methods of constructing the secondary lining. In particular, comparisons are drawn between procurement and mobilisation periods, production rates, flexibility, tolerances and logistics in the tunnels. The technical challenges surrounding cast and sprayed secondary linings are explored, and recommendations are made of how each method could be improved for future use.