SCL primary lining interactions with concrete backfilled temporary tunnels

Using foam concrete or steel fibre reinforced concrete (SFRC) to backfill temporary underground space is a convenient practice for contractors in the tunnelling industry. In the past the SCL primary lining is normally treated as ‘temporary design’, and also possibly because of its difficulty to install monitoring instruments, there is a lack of long term monitoring data. By the advance of modern computational techniques, the experience from Crossrail sprayed concrete lining design for Farringdon, Liverpool Street and Whitechapel stations has shown us many issues that need to be carefully considered before filling voids with mass concrete and building the tunnel partially through it. A summary of Crossrail tunnels being involved adjacent to other concrete backfilled temporary tunnels in Farringdon, Liverpool Street and Whitechapel stations is listed in Table 1.