Thursday, September 19, 2013

Big aquariums and earthquakes

Article

Live stream

I have no faith in the stability of these links, but they should show a live feed of the Toronto aquarium.

Earthquakes

We have no experience on what happens to a big aquarium when the PGV rises.  I think they are probably like large oil tanks.  We might expect cracks at 20 cm/s, and seam rupture at 50 cm/s.

Of all the big aquariums, Boston is at highest risk.  It is probably on a typical raft foundation over Blue Clay, and the design is a big cylindrical oil tank.  I don't think people are at any more risk than a nearby Costco on the same stuff.

Chicago has the least risk, and Toronto is somewhere in between.  I'm interested in Toronto because of the quasi-rock it is on.  When the CN tower was being designed, they drilled 3 exploration holes, large enough to lower a junior geotechnical engineer.  It was in badly mangled shale.  In fact, there was no bedding similarity with all three holes.  They ended up pouring the foundation on the least-bad rock layer, above another clay seam.  The aquarium is on the same stuff.  So, is it rock or soft soil?  We'll never know.

*Note that any earthquake strong enough to bust an aquarium will be such that we don't care.  :)

9 comments:

Gus83 said...

There's a reason the two fall directions of the CN Tower are out into the lake ;-) The one into the city was away from the core, but not so much anymore!

Any idea on how they check their grouted post-tensioning cables?

Harold Asmis said...

I think nobody ever checks these things, even though they go 'ping' once in a while. Everything in a nuclear plant is post-tensioned. Somebody once tried to sell us an internal seismic system to catch the pings.

Anonymous said...

I thought it was solid shale below the CN Tower. Are you saying there is clay layers below the Georgian Bay Formation Shale?

I also thought Chicago had bedrock so deep that they had to raft or pile all of there foundations.

Harold Asmis said...

The Shed looks solid and has an older layout. As well, the seismic hazard of Chicago is low (unless they actually start monitoring). The CN has mucked up shale, most likely bulldozed by ice. There are many clay layers. They didn't want to lay the concrete on a clay layer, so they went in between.

Anonymous said...

If there is clay down there, how did they post tension the structure to competent rock?? I heard that this structure can withstand an M8 quake. Not sure if that is true

Harold Asmis said...

You can drill a tendon a heck of a way down, and get it to grab. It's settlement you worry about. That thing could take any earthquake because the wind loads are much bigger.

Anonymous said...

Is that why se dont see a lot of tall buildings falling in earthquakes, because wind loads typically govern?

Harold Asmis said...

Yes, it's wind over mass, like a sail. The bad buildings are mid-sized, and heavy concrete.

Custom Made Fish Aquariums said...

I also think that they are not paying much attention on the integrity of these aquariums if they'll survive big earthquake hits. Well, I'm not the one checking these stuff so I'm not sure if they do check or not. It's also possible that not only the big aquarium will turn to rubble but everything else when a big quake hits.

-James