Submerged GRP tank - Backfill concrete surround

[MRNot]

I have been asked to design a support for a buried WWTP GRP tank which is 11m long with a 3 m diameter.
The problem is that the tank is to be 0.8m deeper than the maximum burial depth as specified from the tank supplier.
The usual detail is a 300 mm thick backfill concrete surround.
I have designed a rc retaining wall/surround but this seems excessive? I would like to simply have a thicker backfill concrete surround but dont know how to design this. Is there any guidance on this?

 

[dik]

If you're using a concrete surround, can you design it as the retaining structure, c/w concrete roof and not rely on the wall of the tank to provide support? You should check with the tank supplier for this work around. In addition check to see if the tank can be buried deeper using a particular backfill.

Dik

 

[LittleInch]

You need to talk to the vendor, but when I did something similar, it was the overall external pressure which caused a problem. If you state that you're only going to fill say up to 1.5m with concrete, then wait for a day or so for it to set then fill the rest, they may be ok with that, or maybe just fill with concrete up to the top of the tank then wait before backfilling the rest.

Sometimes if you agree to fill the tank with water to the top when backfilling / pouring concrete that is enough to stop the tank getting crushed.





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