In reply to ben b:
> Hopefully the arm came out before the cavers arrived with the dynamite anyway - eek.
Sorry to be a pedant but I see no reference to dynamite in that link...
Quote:"a police helicopter brought cave rescuers with explosives from Flintshire"
It is more likely to have been Hilti caps, normally used to fire nail guns. You drill a hole, push the Hilti cap to the bottom of the hole, insert drill bit, cover everything with industrial conveyor belt material, then hit drill bit with a hammer. The net result is the rock splits locally.
NB. Do not attempt to use the technique without specialised tuition as it can result in major injury.