Friction factor, wood foundation base to gravel

[samclane]

I'm looking for a reference to determine an appropriate friction factor between a treated wood sill plate (square shape) and gravelly sand soil with no backfill restraint.

 

[dicksewerrat]

Drop your 2x10 or what ever on a sand playground and kick it lightly. It will move very easily. all you are doing is placing it on ball bearings.

 

[samclane]

More detail: The wood is 4x12x16" long with a concentric vertical load of 2000 lbs from a steel column / base plate.

 

[cap4000]

Lumber cross grain friction factor on soil is approx 0.50.
Check Reference NAVFAC DM7.02 for other typical cases listed.Good Luck.

 

[cbosy]

The DM-7 says .5 for wood on masonry. I would use .25 to be on the safe side for soil. I assume this is treated wood?

 

[cap4000]

Cbosy

I use for rubber tire traction coefficients on sand and gravel approx. 0.3 to 0.4. My guess is wood should be a little higher,thus 0.5 is my estimate.

 

[PEinc]

Lindeburg's Civil Engineering Review Manual, Third Edition, Table 10.4 says the friction angle for masonry on wood is 26 degrees. If f = tan(26 degrees), f ~ 0.49. I'd say friction for untreated wood on gravelly sand should be about f = 2/3 tan(35 degrees) = 0.46. For newly treated (slippery) wood, I'd probably use even less, maybe 66% x f = 0.30. That's just my guess.