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: Re: Metro Tunnels might utilise tunnel locos?

Philip G Graham
 

Stuart

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!

-PGG-

Stuart Thyer
 

Hi Phil

In the last day or so, hoarding has gone up along the fence revealing that the site in question is in fact part of the metro train project. The site is the 'Marrickville Dive site' and according to the project web site, will be the launch site for 2 TBMs. 
A closer look at some of the material stacked on site revealed that there are track panels constructed on steel I beams, the track running longitudinally along the I beams, which are spaced appropriately for the gauge (whatever that actually is). Presumably these are for the TBM to run along, but I have no experience in how these sort of tunnels are constructed. Hopefully this info might be of use to you, happy to keep an eye on the site as works progress.
Stuart

Philip G Graham
 

Stuart

Yes, more encouraging. There seems to have not have been an announcement as to which TBM manufacturer is to supply these yet.

For the initial assembly of the TBM there needs to be an external cradle structure to support the circular shape of the the shield until it starts its penetration. The TBM back-up is the name for the trailing support equipment which runs on either wide gauge rails or rubber tyres on the ring surface - behind the actual boring head, and is where the ring segments are placed in position. After each ring is completed, the TBM hydraulically thrusts forward off this ring, boring the next length by a similar width of the ring. For the initial launch a frame structure is used to enable something for the TBM to thrust against until sufficient rings are in place. Advance rates are usually quoted by how many rings are placed daily, weekly, etc.

If there is to be a construction railway delivering ring segments, then it will become apparent when the back-up is being assembled, if this is within public eye view. Is the Marrickville site reasonably open? i.e. not down the bottom of a deep shaft? The conrail or the MPVs run directly into the interior of the back-up.

I would say that the Melbourne sites are going to be much more confined, but this does not necessarily rule out a conrail operation.

-PGG-