Scott Wilson Railways has completed a gauge clearance scheme with Alfred McAlpine for the Ipswich Stoke Hill tunnel in the UK (T&TI, May 2004, p10).
The 330m long tunnel was originally built in 1846 and is at the London end of Ipswich station. The tunnel was to be modified to allow clearance for freight containers to Felixstowe. The twin track tunnel is built on a curved horizontal alignment and has an arched brick invert. To achieve the gauge clearance, the track had to be lowered by up to 300mm.
A laser scanning system was used to profile the internal surface of the tunnel to an accuracy of +/- 5mm.
