Saturday, December 3, 2016

Geotechnical Engineering - Quicksand

I've seen a lot of excavations in Toronto have that most dreaded of problems - quicksand.  This is when the hydraulic gradients are so large as to lift sand particles, making a thick soup.

This excavation has been stalled at this exact point for weeks.  And they have a pump going all weekend.  All they do is walk around with worried looks.  I haven't asked anyone because they'd be looking for an extra few million dollars for freezing.

The excavation is for jacking in a sewer liner.  It is deep and has to be very stable because men will constantly be working in it.  They could have paid an extra 10 bucks when they were doing the soil drilling, for a pumping test, but I guess they didn't.  An old-school geotechnical engineer would have seen it right way, but nobody employs them any more.

It's just the delay that is costly.  The contractor will sue for extras, so he's okay.  This is just consistent with all the other jobs on the river.  :)

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