Approaching quicksand from below...

[Lomax]

...which sounds a clever trick, doesn't it?

I've been reading a biography of Richard Trevithick, one of those engineers of genius that Britain threw up during the Industrial Revolution. He is best remembered for being the first man (1804) to design and build a steam-powered locomotive that ran on rails - and if he has been overshadowed in the world of steam by men such as Watt and Stephenson, it is because his vast talent as an inventor was matched by his equally impressive lack of business sense.

He also had a butterfly mind. He was always branching off into new projects, so obsessed was he by the idea that steam-powered machinery could do almost anything. He built what might be considered the first automobile in 1801, and also designed machines for mining, farming, dredging...

...and tunnelling. In 1808-9 he led a team that sought to dig the first tunnel under the Thames. As ever, he was pushing the frontiers of unknown technology; and he found that you can actually tunnel your way into patches of subterranean quicksand. In particular, if you tunnel underneath a patch of quicksand, it has a tendency to let the river in. The tunnel was flooded. Nothing daunted, Trevithick proposed a solution, which was to sink a caisson in the middle of the Thames (this at a time when no-one had ever done such a thing) and plug the hole from there. At this point his backers got cold feet and pulled out.

But anyway. Our interest pops up in the oddest of places.

[Mynock]

The lack of load bearing capability is what we love.
He was on the right track with the caisson. Most modern tunnel boring machines have a built in mechanism that inserts a concrete liner. They don't just dig the hole they actually build the tunnel too.
http://www.youtube.com/watch?v=qx_EjMlL ... lpage#t=88

[Mynock]

They were under a river, so it was probably just the result of not going deep enough to avoid the saturated bottom sediment. Tunneling under bodies of water is a complicated prospect even with todays tech, I can't imagine trying to do it with early 19th century equipment.

[nachtjaeger]

Yeah. My hometown had a vein of quicksand running under it. There was one spot on a busy street where the pavement would constantly sink and make a 1 or 2 foot wide pothole. So the town crew would come and patch it. This happened for many, many years. When they rebuilt the road, they found a cylinder of asphalt going down into the ground at that spot, the result of years of putting patches on patches.

Supposedly junk from the old town dump was found coming out of a hillside 1/4 of a mile away downhill, but I never confirmed that one myself. I do know that some of the older homes in that area were build with special low-ground-pressure foundations.

Very interesting! I wonder if that means there are places where we are walking,that actually have quicksand far beneath?

[Billie Bonce]

Very interesting! I wonder if that means there are places where we are walking,that actually have quicksand far beneath?

Of course there are such places, a lot of them! It's a normal geological formation, more common than quicksand on surface. In Russian it has different name, other than for surface quicksand. The problem of such places was known for centuries. It was the main danger for those who were digging wells. If they reached such layer in a deep well, the sand saturated with water poured into the well (it was stable under pressure of the ground above it, but instantly turned into "quick" state as soon as the pressure was eliminated). Very often there was no time to pull the man who was down there up and out of the well - in just few seconds he was stuck in quicksand, and then, soon, drowned.