Long-term settlement following SCL-tunnel excavation

Whitechapel station comprises two deep excavations extending from ground level down to the platform tunnel level, one at Durward Street (DSS) and one at Cambridge Heath Road (CHS) (Figure 1). The station at depth includes two main station platform tunnels at 24 m below ground level (bgl) each about 11 m in diameter. Various connecting cross passages, escalator tunnels and emergency escape routes are constructed between the platform tunnels and connect with the deep excavations. Excavation of the Whitechapel station tunnels was completed between 2012 and 2015.

All station tunnels were excavated using the LaserShell^™ method with sprayed concrete as primary and permanent support. LaserShell^™ was first developed for the Heathrow Terminal 5 tunnelling works, details of which can be found in Eddie and Neumann (2003 and 2004) and Chapman et al. (2010) ^{[14],[15] [16]} . Excavation has been done in two stages. First: Excavation of a ∼6.5 m diameter Pilot Tunnel; full face excavation with advance length of 1 m. The Pilot Tunnel was followed by the excavation of the ∼11 m diameter Enlargement comprising two 1 m top heading advances and a 2 m-invert for each two meter full ring closure. The EBRT comprised construction of ∼6.5 m diameter Pilot Tunnel followed by enlargement to ∼9.5 m diameter using the same excavation sequence.