BM> This brings to mind something I saw up in that area (don't
BM> know what state, but I'd guess it was in New Jersey,
BM> Delaware, or Maryland) about 30 years ago:  On the approach
BM> to a tunnel, there were signs saying that vehicles with, or
BM> pulling trailers with, gas bottles were not to use the
BM> tunnel, but were instead to use an open-air route.  The
They had the same sign in Virginia about 8 years ago.
BM> other route.  Might some tunnels have less than optimum
BM> attributes?
No.  Its not the explosive factor that they are worried
about.  If you look a little closer at the sign you
would have seen that tankers w/ non compressed
flammable materials were also not allowed.  Personally
I'd be surprised it any tunnel allowed them.  The
reason is an accident involving them could pose a
suffocation threat when/if the gas ignited and consumed
the O2 in the tunnel.  Compressed gas such as propane
spreads faster than a flammable such as gasoline and
therefore would consume O2 at a greater rate.
If you could fill a tunnel with hydrogen and oxygen and
ignite it that MIGHT damage the structure but with
nothing to concentrate it the force would blast out
each end of the tunnel.
If anyone really gives a care I can try to find a demo
card which gives the amounts of various explosives
needed to breach different materials.  There are
several factors you have to take into account; the
explosive, the shape of the charge, if the charge is
tamped (has something placed on it to contain the
force), where the charge is placed, what the wall is
made from, what is behind the wall and how big of a
hole you want.  And those are just the basics.
                      Remember:  Freedom isn't Free!
--- timEd-B11
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