Soil/concrete friction for precast concrete.

[MTJack]

Is the coefficient of friction between soil and concrete different for CIP concrete and precast concrete? I have been given a value of .25 and this is much lower than I can find in any other source.

 

[jayrod12]

I would say it depends on the soil but in weak soil I've had that number and lower even.

 

[Doctormo]

Yes the coefficients are different between CIP concrete and precast. Poured concrete will generally bond with the soil in some irregular fashion so it may or may not have an dissimilar material interface sliding coefficient. If the surface is irregular enough from the pouring and foundation preparation, the sliding coefficient becomes closer to the soil shear strength (such as 80-100% of Tan(phi)). Precast will never have a good bond with the soil unless the bottom is fabricated with roughness to engage the soil. Typical values for CIP concrete might be 0.30 to 0.60 depending on soil and precast will be always be lower.