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Coefficient of Friction - Concrete Block on Gravel

Coefficient of Friction - Concrete Block on Gravel

(OP)
I am looking for reliable numbers for the coefficient of friction between a precast concrete block and gravel, and or soil. This is to provide lateral shear resistance in temporary construction activities. I found some references for cast in place foundations, but the "deadman" counterweight is precast, not cast over the roughened surface. I think of this as a polished concrete block, sitting on a rough surface, just a little bit better than sitting on ball bearings. I need positive anchorage, but I am restricted from penetrating the grade, do to unknowns.

Can anyone help?

Thanks so much in advanced.

RE: Coefficient of Friction - Concrete Block on Gravel

Simple to test. Do that.

RE: Coefficient of Friction - Concrete Block on Gravel

The CalTrans Falsework manual (4-5.09) allows mu=0.6 for concrete anchor blocks on dry gravel (or 0.4 for wet gravel).

I've always treated that with a little skepticism due to the potential ball bearing effect -- either requiring a thick pad of well graded gravel with some photo evidence, or discounting the factor a little. But I have used it with those caveats with success in the past.

RE: Coefficient of Friction - Concrete Block on Gravel

(OP)
Thanks guys. These are the numbers I had, but you confirmed what I was thinking. If situated just right, this has no lateral capacity. Testing sounds great, but this is outside of my scope and budget. Supply of the blocks is by others, and liability of the anchor is by me. Trying to get the notes right to limit my exposure and risk. I am going to reduce these numbers by a FS of 2:1.

Appreciate the help.

Sincerely and regards,

Barry D. Jackson, P.E.

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