^^ A lot of tunneling is done under pressure, especially where the soil is likely to collapse such as the storm water system tunneled beneath Cairo in the sand.

But that reminds me... and I'm very bored with no-one to talk to...

When I worked on the channel tunnel (which was in chalk marl, not prone to collapse and therefore not tunnelled under pressure) there was one weekend when all the miners were very nervous... there had been some mystic in The Sun who had predicted some kind of disaster, which the miners had interpreted as the tunnel collapsing. They kept asking me if everything was OK? ... I was only a young geotech at the time, but had some kind of responsible look I guess. I re-assured them, but even at that tender age 30 odd years ago couldn't help but mention that anything could happen, mind you. We hit a fissure in the upper chalk and water started pissing through... and a load of miners started legging it back down the tunnel. Had to laugh... if I wasn't so shit scared as well.

I nearly had my worst industrial accident working in the channel tunnel. We worked about 3 miles out in what was called the cross-over chamber. I didn't work regular shifts so had to try and get out of the tunnel, back to the office, to finish up my work without waiting for the regular change of shift trains. The spoil trains from the TBMs passed by our work site every now and again carrying spoil from the tunnel face back to land, and each spoil train had what they called a 'manrider' carriage at it's end, just for people like me. These trains wouldn't stop for us as it was too difficult to start up again (and they were working to bonus) so just slowed down as they went past, and we had to jump into the back of the manrider while it was still moving.

One time I jumped in, skidded across the carriage and nearly went arse-over-tit out the other side, in front of another train coming from the opposite direction. A big miner stopped me heading out to a probable nasty death.

Investigation showed I'd skidded on a big, wet, slippery paddy turd. The paddy miners used to take their morning constitutionals in the manriders which were cleaner than the toilets on offer.