"Dave Eadsforth" wrote in message
...

So, what to we conclude when a country orders a set of tunnelling
equipment, ostensibly to build a metropolitan subway, and then gives up
'because the geology is all wrong' (um, wouldn't that have come out of
the original survey?)? Is the kit sitting in a junkyard - or is it now
underground, doing something else?

For deep hard rock mining you use drilling and blasting techniques
(commercial explosives and BIG drills). This is how the South African gold
mines extract over 130 million tons of rock (and gold ore) every year from
as deep as 4km (2.5 miles) - with plans to go deeper in future. Modern
tunnelling equipement as you discuss only work in soft rock. So you would
have to stop anyone who has access to simple commecial explosives - which is
simple to manufacture.

Da vid