Soil bearing under a ringwall

[Bartek22]

Hi guys,
We are just calculating foundation for a tank 25m wide (diameter) and 12m high.
Can somebody tell me a quick way to calculate soil bearing pressure under this wall.


Thank you in advance for your help.

 

[civilperson]

Weight of the ring wall and weight of the tank wall and weight of the roof and weight of the fluid directly over the ring wall divided by the area of the bottom of the wall.

 

[Bartek22]

Civilperson - Thanks a lot. I thought so but I wasn't sure. Have a nice day

 

[gwkwong]

I think there should be a weight due to wind over-turning.

 

[BigH]

I believe that Bowles book describes design of circular ring foundations.

 

[4ntunes]

Bartek22,

The first step is to determine the soil allowable bearing pressure. You can make use of any given theory of soil mechanics. For this, I suggest the slip lines method given by Sokolovski (1960.1965).
After determining the allowable soil pressure, you must find the maximum pressure applied to the soil structure. At this time, should be considered all loads acting on the structure, including vertical and horizontal loads. Make a combination of loads and investigate the following hypotheses: 1) tank full (fluid or water, the worse case) + wind loads 2) tank empty + wind.
In short, you get two types of loads acting on the basis: Flexion moment (M) and vertical force (V).
Calculate the eccentricity: e = M / V. Note that the eccentricity "e" must be less than 0.59 according to German Standard DIN 1054 (1969).
After obtaining the maximum pressure applied to the soil, you should compare it with the maximum allowable.

It is important to emphasize that the displacement of the structure of the tank is critical in setting the allowable soil pressure. Remember that the geotechnical foundation design comes down basically to check the pressure of the soil and settlement.

For the design of the ringwall, you can see the API650. Also remember to check the ultimate limit state of fissures opening.

 

[BigH]

I probably wouldn't use a ring wall. (note - this has been a contentious issue with many falling on both sides of the discussion).

 

[kslee1000]

BigH:

What type foundation you would suggest, and its advantages? Hope you don't mind to spend sometime on these questions. Thanks.

 

[hokie66]

I think BigH may be tired of discussing this subject, as he has already done it a few times. Suggest reading the following thread, and others covering the same topic. There are a lot of them.
thread507-219486

 

[BigH]

Thanks hokie!

 

[hokie66]

No worries, mate!

 

[Bartek22]

Thanks a lot guys,

4ntunes - great explanation, thank you very much. Finally I have calculated that tank (and 3 others) according to API650 and our client requirements, however your tips will be very useful in the future.

BigH - Ringwall has been required by a client. I had nothing to say. And the other thing...Now I know that there's a lot of threads - beginners mistake

The rest of you - big thanks

 

[4ntunes]

If you need any more help, post the issue here so I or another engineer perhaps can help you again. In your specific case, I assume the ringwall is cheaper than others tipical storage tank foundation and it was the reason your client has chosen it.

Sorry for my poor English.

Regards

 

[BigH]

4ntunes - no need to keep saying sorry for your English - it is fine!