Mud Mats

[Dad2one]

Hello,

Contractor wants to place a mud mat under a cantilever retaining wall footing. I'm ok with that in principle but was wondering if I should require a minimum thickness and if so, why. Frankly, I'm more concerned about the effect on the coefficient of friction for sliding. Does it make sense to use the 0.6 factor from shear friction for the concrete-to-concrete surface? Seems a little high to me. He's proposing 2500 psi concrete with 4" slump. Site is just south of Nashville, TN and allowable soil pressure is 4ksf.

Thanks.

 

[hokie66]

I wouldn't worry about the concrete to concrete friction. Just rake the surface. Whatever you do, the friction of the concrete will be greater than at the concrete to soil interface.