k values

[civeng800]

What lateral earth pressure coefficient(k) is typically used for good drainage backfill? What can be used for 1" gravel?

 

[Focht3]

<[blue]Focht3[/blue] sighs deeply...> There is no such thing as &quot;the&quot; k-value. And &quot;the k-value&quot; isn't even a property - it's a numerical convenience. Do a search of this site for &quot;k-value&quot;, &quot;Winkler&quot;, and &quot;subgrade modulus&quot; (a related topic to your question) to see what has been discussed previously on this site.

Please spell out your problem in detail, and we'll try to provide thoughtful - and helpful - responses.



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[PEinc]

I think he's asking about lateral earth pressure coefficients, not subgrade modulus.

 

[Focht3]

Yup. I stand corrected.

The appropriate earth pressure coefficient will depend a lot on the material. The angle of internal friction, &[ignore]phi[/ignore];, of the material will depend on both the density and angularity of the material. Smooth, well rounded particles will have lower &[ignore]phi[/ignore]; than a crushed rock material. Values of &[ignore]phi[/ignore]; for rounded materials will range from about 32&[ignore]deg[/ignore]; to 37&[ignore]deg[/ignore]; while values for a very angular crushed rock material can reach 40&[ignore]deg[/ignore]; - or more.

You can check with some of the other engineers in your area to see what is commonly assumed; but don't forget to discuss this with the project geotechnical engineer...



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[Myoho]

If your still looking for values I would suggest a Ka = 0.27 and a Kp=3.7 (if you are considering using Kp). I think these coeffs will be reasonably conservative for the material you suggest.

Rgds,

Rob.