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k values

k values

k values

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

RE: k values

<Focht3 sighs deeply...> There is no such thing as "the" k-value.  And "the k-value" isn't even a property - it's a numerical convenience.  Do a search of this site for "k-value", "Winkler", and "subgrade modulus" (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 VPL for tips on how to make the best use of Eng-Tips Fora.

RE: k values

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

RE: k values

Yup.  I stand corrected.

The appropriate earth pressure coefficient will depend a lot on the material.  The angle of internal friction, φ, of the material will depend on both the density and angularity of the material.  Smooth, well rounded particles will have lower φ than a crushed rock material.  Values of φ for rounded materials will range from about 32° to 37° while values for a very angular crushed rock material can reach 40° - 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 VPL for tips on how to make the best use of Eng-Tips Fora.

RE: k values

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.

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