Buckling check of External loaded deep lift station

[M Eng]

Hi Colleagues,

I'm working on the design of a large diameter deep sewage lift station(50m dia and 60m depth). I was wondering, is there any check that ensures the concrete walls of the well will not be buckled under the high pressure load.
Any ideas to do such check?
Any reference that discusses this issue?

 

[human909]

60m deep sewage! Well you are in some deep shit there Sir.

 

[TLHS]

I'd done a couple of well type deep excavations, but am not an expert at this. This is a pretty big item that takes a lot of coordination with the geotech guys and with people responsible for installation strategy. There's lots of checks, but it's pretty dependant on how it gets installed and what the ground conditions and water table look like. Unless someone's able to tell you that, or you've done this enough to take it on yourself, this is not a thing you should probably be doing without a reasonable amount of integration with a contractor.

 

[JStephen]

Interesting question.
There is a lot of literature and code provisions for metal cylinders under external loading. That question comes up in pressure vessels, in steel tanks, and in submarine design.
Some of this would presumably be usable on a "thin wall" concrete cylinder, where buckling mainly depends on modulus of elasticity.
The problem is that for thicker shells, the allowable external pressure is based on material properties beyond modulus of elasticity, so that information would be less applicable to your case.
Just googling the question, I come up with some hits on the topic, but the authors are dealing with 500mm diameter models, not 50m, so it's not entirely clear that the information would carry over.
My guess is that if you consider the bending effects of unequal loading/ backfill, and the potential for uplift due to buoyancy, then buckling will not be an issue.
It is possible to consider buckling in finite element modeling, but that's not a topic I know much about. But that might be the approach to use regardless, due to the unequal-loading design and the overall cost of the project.

 

[SWComposites]

good general reference source for shell buckling:

https://shellbuckling.com/index.php

(though probably does not have much specifically on concrete shells).

two key things to be defined: the detailed loading, and the expected imperfections in the shell.