Philip G Graham
Interesting project. The requirement to retain heritage integrity rules out the approach made by the TGR in Tasmania to use an existing TBM (tunnel boring machine) to ream out the diameter of the Rhyndaston Tunnel on the Main Line between Hobart and Launceston, for a similar clearance problem.
Tasmanian Transport Commission, Tasmania - Expansion reaming of Rhyndaston rail tunnel - HEC/TGR jv - Robbins TBM-Main Beam Open Gripper #161-108 "The Mole" 4.93 m x 945 m (_/64~_/65)
TGR utilized the ex-Hydro Electric Commission Robbins hard rock TBM that had previously been used on the Poatina HEP project head and tail-race tunnels, some 6 800 km of successful tunneling.
For the railway based project, the TBM was partly mounted on the TGR heavy duty well wagon P2 (previously used for transformer and generating machinery transport) and the remainder of the TBM traveling on the heavier rated bogies from a withdrawn M-class tender. This was a requirement as the reaming machine was to be withdrawn from the tunnel during daytime windows to allow regular train working to continue.
This project progressed relatively quickly as the material being shaved out was the softer, but abrasive Tasmanian sandstone. Unfortunately, the "heritage" brickwork forming the portals at either end of the Tasmanian tunnel was destroyed and lost in the process here.