Underground tank simulation

Simulation
1

Hello@tous

I'm stuck on a simulation to determine the thickness of an empty tank under the Saharan sand, I'm considering simulating with a fluid with a density of 1900+200 kg/m3 (wet sand density), but I have the impression that the behavior of the sand particles doesn't stop there, especially with the seismic effect.

Any suggestions, thank you in advance. 

2

Hello LInk

Are you going to use SW simulation or Flow simulation?

What do you mean by seismic effect?

Can you specify the depth in relation to the diameter? In other words, if the cistern is buried with 2 or 3 m of sand on top, it is not the same as if the cistern is flush with only 50 centimeters of sand on top. Also, the outer surface of the tank is in direct contact with the sand or placed on a raft.

If the cistern is buried at 1.5 times its diameter, it must be possible to consider that the pressure is uniform like a bathyscaphe at a depth of 20 metres. On the other hand, a very stupid thing that I saw in the Navy Nat is when a relative vacuum is made in the tank because of condensation and the change of temperature or the withdrawal of the liquid without venting. The tank deformed and almost collapsed on itself.

You know this better than me but for the simulation don't forget to close (blackout) the tank completely.

Your subject is very interesting ;-)

Kind regards

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3

Hello @Zozo_mp and thank you for taking the time to answer me.

Regarding the remarks:

  • I plan to use sw simulation,
  • For the seismic effect I believe that the sand becomes more and more compact, also the phenomenon of liquefaction which in my opinion influences the pressure exerted on the cistern walls, the latter is in direct contact with the sand, thus attached to a raft, 
  • For the diameter of the tank it is 1.9m, totally buried with only 0.5m of sand on top.
  • For the interior, the tank is ventilated, not supposed to contain fluids but rather equipment, 
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4

Hello@Lynk

For liquefaction, it reduces the pressure since the ground becomes totally soft: a bit like if you were injecting water or air from the bottom. On the other hand, it is the next phase called compaction that it fears for your tank.
So there are two solutions: either work on the ground before installing the tank, or put small circular reinforcements on the external or internal walls as for the annular compartments, or a double-walled tank (see standard EN12285-1) with a neutral fluid between the two walls, which is often recommended are the anchors by belts fixed on a radiator or in a casing.
That said, what also counts is the weight of the equipment, if the weight is too small, the tank floats, if the weight is too great, it sinks or sinks deeper into the ground.

After all, it all depends on the stakes.

https://www.carbura.ch/fileadmin/user_upload/editors/web_dokumente/pdf_dokumente/LKT-KooVG/Grundlagen/Aktennotiz_Erdbeben_V6_20180320-fr.pdf

https://www.uic.fr/content/download/331580/3705672/file/DT_106_Seisme_MethodologieGenerale_201410.pdf

http://www.es.lafon.fr/IMG/pdf/Low_39000012_citernes_cylindriques_a_double_paroi__Ind_F.pdf

Kind regards

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5

Hello @Zozo_mp I hope you're doing well,

The information and leads were a great help to me:)

See you soon. 

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