tank concrete ring foundation replacement

[domagoj]

There was good article about concrete ring foundation for tanks thread256-163185
I am mechanical engineer, and I have project where tank D=30m concrete ring foundation has to be replaced.
I am looking for procedure and details for supporting tank shell during execution of this operation.
Thanks
PS I dont know how this (mining) comes with my name but never mind

 

[BigH]

Can you please advise as to why the concrete ring foundation has to be replaced? I think this is an important aspect to understand before indicating possible means such as underpinning, "sandwiching" the existing ring foundation, etc.

 

[domagoj]

Settlement has occured with the tank and it is required to lift it back to an elevation within the above acceptable limits, the existing ring wall need to be demolished and the contractor shall design and construct a new concrete ring wall as per API 650 requirements

 

[IFRs]

Jack up the tank, support it properly, dig out the ringwall and pour another. Done!

 

[msucog]

to add to bigh's question, i presume someone has looked into the how's and why's the thing settled in the first place and whether it will settle more in the future or if the settlement has slowed sufficiently? it's not exactly what you're asking, but again, it could provide some direction as to the most practical solution. also, it might expand the work scope of what needs to be done while you're going through the trouble of replacing the thing.

 

[BigH]

Getting back - has the whole tank settled or just the ring wall? Is it general ground settlement? You've got a big tank and if the whole thing has settled (uniform settlement (realizing of course that the centre will settle more than the edges - Boussinesq and all that), what does replacing the ring wall going to do? You bring the ring wall (tank edge) back "up" and the centre of the tank is still down. The next question is, and this depends on how much it has settled, how has it affected the "performance" or use of the tank? So long as you have flexible connections, it can settle and not cause any performance problems. I never liked ring walls anyway - we just put the tank on a granular pad of select sand and gravel and make it about 5 to 10 ft larger in radius than the tank.