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Allowable Bearting Capacity vs Soil Modulus

Allowable Bearting Capacity vs Soil Modulus

Allowable Bearting Capacity vs Soil Modulus

(OP)
Excuse this basic question from a humble mechanical engineer.

I am interested in the design of buried flexible pipelines. The geotech reports I receive refer to allowable bearing capacity in kPa. How can I relatye that to the soil modulus in order to use the Spangler equation to design trench and pipe for a gravity main.

Are there classic papers or books, perhaps even software, that can allow me to interpret the data to enable the calculations to be performed.


RE: Allowable Bearting Capacity vs Soil Modulus

I have a paper which describes the methods used for calculating spring constants for buried pipe based on soil properties, but its probably the type of thing that needs to be done by a geotechnical engineer.  The type of properties used in the analysis are not usually listed in a common geotech report.  

As far as relating bearing capacity to soil modulus, one needs to know the amount of settlement which will be caused by the applied contact pressure.  Soil modulus is based on soil response (ie. the amount of settlement for a given load).

Let me know if your geotech could use the paper

RE: Allowable Bearting Capacity vs Soil Modulus

(OP)
The papaer would be very helpful. I would discuss with with a geotech engineer.

Paper could be emailed to geoff.stone@lendlease.com.au or faxed to 61 2 8850 2324.

Regards

Geoff Stone

RE: Allowable Bearting Capacity vs Soil Modulus

gibbycu,

I too would like a copy of the paper you mentioned.  Please send via e-mail to jheidt2543@aol.com.  Thanks in advance.

RE: Allowable Bearting Capacity vs Soil Modulus

Its been sent to both of you, I hope it helps

RE: Allowable Bearting Capacity vs Soil Modulus

Geoff -

Gibbycu is right - you will need a geotechnical engineer to assist you.  There is no direct correlation between modulus (stiffness) and bearing capacity ("yield strength") for soils; nor is there one for steel, aluminum, copper, etc.

How big is your pipeline?  What materials are used?

RE: Allowable Bearting Capacity vs Soil Modulus

Stanier:

If you already have an allowable bearing pressure given in a geotech report, usually the modulus of subgrade reaction can be estimated from the allowable bearing pressure by the following relationship:

Ks = 36 x qall
where:
Ks = modulus of subgrade reaction in kips/ft^3
qall = allowable soil bearing pressure in kips/ft^2

in SI units the same equation will be:

Ks = 120 x qall
where:
Ks = modulus of subgrade reaction in kN/m^3
qall = allowable bearing pressure in kPa

these equations consider a factor of safety of 3 and a maximum settlement of 1 inch, which is typical by geotech eng in providing a qall.  reference to this relationship can be found in Foundation Analysis and Design (5th ed.) by Joseph E. Bowles, 1996. McGraw-Hill, page .

Also this is referenced in the U.S. Army Technical Manual TM 5-818-1 Soils and Geology Procedures for Foundation Design and Other Structures (Except Hydraulic Structures)page 10-5.  This manual can be downloaded from:

http://www.usace.army.mil/inet/usace-docs/armytm/tm5-818-1/

Hope this gives a quick check for your findings.

CIS Geotechnical
jrodriguez@centralindustrialpr.com

RE: Allowable Bearting Capacity vs Soil Modulus

gibbycu,

Às other members in this forum.... I too would like a copy of the paper you mentioned.  Please send via e-mail to jrodriguez@centralindustrialpr.com.

Sorry for bothering, but this forum is the best I have found for sharing information that is out of print or difficult to find.

Thanks in advance.

CIS Geotechnical
jrodriguez@centralindustrialpr.com

RE: Allowable Bearting Capacity vs Soil Modulus

I, too, would like a copy of the paper.  Could you please email it to me at jhewitt@transtechsys.com .  Thanks.

John

RE: Allowable Bearting Capacity vs Soil Modulus

I don't like Bowles, and CISgeotechnical has provided a perfect example of 'why'.  Bowles' equations involve quite a few assumptions: do you know what they are?

Don't use equations you don't understand -

RE: Allowable Bearting Capacity vs Soil Modulus

dear gibbycu,

i too would like a copy of the paper you mentioned. apprecaite if you could e-mail a copy to
wong_kt@wohhup.com

Thanks in advance.

regards,

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