Philip G Graham
In my readings to date, the WestConnex project contractors are going for NATM tunnelling with roadheaders - nasty looking beasts with arms topped by whirling balls of very sharp teeth!
The reason is partly because the cross profile of the multi-lane roads will be to a 'Horseshoe' shape. To utilise a TBM would require one of a very large diameter similar to those previously used in Brisbane and Auckland which not do render a suitable lane layout for WestConnex. Another method could have been a smaller diameter TBM and to ream out manually (with roadheader) the remaining profile to suit. Lining is shotcrete and concrete walls/ceilings formed with moveable shutters.
As it is, TBMs will not be used there, and these NATM projects generally use pneumatic-tyred vehicles to dispose of the muck. On the other hand TBMs of rail-sized profile renders a pre-lined envelope of circular profile ideally suited to a rail loading gauge. In the servicing of these latter TBMs, it can be either way, by conrail or the dreaded MPVs - hence our (my) anxiety!