On Tue, 8 Jul 2003 08:34:12 +0100, nightjar wrote:

You do need to have a large stone tower on top of it for this to work
though. The bit you missed out is that, as they dug under the defences, the
miners put in a large number of very heavy wooden supports, to stop the
tower falling down on top of them. The fire was to burn the wood away,
allowing the tower to fall under its own weight. Fred Dibnah demonstrated
this technique on TV, when he was demolishing a building. He also
demonstrated how difficult it is to know just when the timber is about to
give way and ended up running off the site as bits of masonry started to
fall.

You may be correct - but that's not entirely the way I understood it.

Yes, for sure you need to prop up the structure above. But the damage
to the concrete comes about because the concrete gets some localised
heat which it doesn't dissipate very well. And it can't expand and
contract like (for example) a piece of metal. And so it shatters.

However I'm happy to accept that I could be wrong.

Andrew

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