Coefficient of Friction b/w Concrete and Soil

[aueng06]

Hello all,

I'm trying to prove that a foundation design is adequate for sliding for a soil having an effective friction (phi') of 37 degrees. Is the coefficient of friction (mhu) between the concrete and the soil equal to the tangent of the effictive friction (37 degrees)? I want to double check to be sure that this basic soils formula applies between the soil and the concrete and not just soil to soil. Any thoughts would be greatly appreciated.

 

[jmgray]

Phi is an internal friction angle - (phi') is the friction angle under drained cases, (phiT) is the friction under undrained cases. A coefficient of friction for cast-in-place concrete to soil is =tan(0.7*phi') or =tan(0.7*phiT) depending on site conditions & rate of loading.

 

[fattdad]

I'd agree: take two-thirds of phi and then the tangent and you'll be close. Figuring out how to best evaluate phi is the hard part. This discussion is somewhat dangerous as for clays, who's to say that the ultimate strength will be based on long-term "drained" loading conditions (as referenced by jmgray.

f-d

¡papá gordo ain’t no madre flaca!

 

[aueng06]

Thanks for the help. I'm still not quite sure what I need to do to solve my problem, but I do know that I need to investigate further into my geotechnical report.

 

[kslee1000]

We used to check sliding stability on sandy/rock material by the following method:

H/(V-U)*Tan(phi)>= 1.5 (S.F.)

V = total weight above shear plane
U = uplift against sheat plane
phi = soil internal friction angle

For clay, the apparent cohesion factor "C" was used.

 

[FiratPCR]

http://www.usace.army.mil/publications/eng-manuals/em.htm

You can check EM1110-2-2100 and EM1110-2-2502 I am sure that it would help since I did same kind of work recently. It was related with Retaining Wall Stability.

 

[Mccoy]

Some guys reccomend in granular soils use of Phi-CV (Phi_constant value) to verify sliding of foundations.

If you accept that your phi would be only a function of grain properties and mineralogy, not soil relative density. It makes some sense since it's hard not to disturb the soil at the bottom of an excavation...