Re: Tunnels

["Ron BESDANSKY (formerly Ron BEST)" <ronbest@bigpond.com>]

MattyQ <matticueQ@corplink.com.au> wrote in message
37aacbdd.0@news.bris.corplink.com.au">news:37aacbdd.0@news.bris.corplink.com.au...
>
> I guess now would be as good a time as any to ask the question "What is
the
> definition of a tunnel?". Most stated in this thread clearly qualify as
> tunnels but some are questionable.
>
How about: A tunnel is a space excavated in the earth to accommodate a
railway (or other means of transport), whether or not the excavation was
carried out by the "cut and cover" method or by boring or excavation where
an amount of original ground was left between the soffit (top of the tunnel)
and the natural ground level.

On this definition: Tunnels include:
Cleveland Street (Sydney Central-Redfern, NSW);
All "underground" sections in Sydney & Melbourne;
Boronia (Vic) and Subiaco (WA)
The roofed-over cutting on the Rozelle (former Darling Harbour) line
(Sydney) between James St and Derbyshire St, even though the "cover" was put
on long after the cutting was excavated
Railway Square (Powerhouse Museum siding, formerly Darling Harbour line)
(Sydney)

But the following are NOT tunnels:
Railway overbridges where the railway lies at the natural ground level and
the road or other crossing way is elevated (e.g. Armco culverts and most
road overbridges);
 The covered-over sections of the Sydney Light Rail line at Pyrmont Bay and
the casino, because these are structures built over a railway which is laid
at the natural ground level.

The operative criterion is that the railway has to be BELOW the NATURAL
ground level.
Rgds

Ron BESDANSKY (formerly Ron BEST)