Shear Resistance of Rebar in Compacted Soil

[Trillers]

To secure formwork into compacted soil the contractor is using a 2x4 base plate and using #5 rebar driven 16" into the ground to anchor the base plate.

The loading on this will be the horizontal load from wind forces and horizontal forces produced by the uncured concrete and the vertical forces generated by wind.

To determine how much force can be resisted by the rebar anchor, I'm assuming for shear, as for a simplified procedure similar to that of soldier piles, the soil compressive strength would control the resistance to shear.

Not sure how I would compute pullout resistance of the rebar in the compacted soil?

I have searched quite a few references including AASHTO but with little luck. Hoping someone can steer me in the right direction.

Thanks.

 

[BridgeSmith]

We consider that contractor "means and methods". We don't review it, and we don't comment on it. The contractor is responsible for making sure his formwork stays in place.

That said, the pullout resistance would be minimal - a few hundred pounds, at best.

 

[WinelandV]

At my first job (working for a contractor), I was tasked with something similar - and couldn't get it to calc out, not even close. They wanted to use a formwork pin (you know, solid steel, 3/4" ish diameter, 2' long or so) as a means to resist the thrust.

What ended up happening is the field did a lateral load test on a bunch of pins and they were able to show an ultimate capacity of 1000's of pounds.

Big caveat - the pins were hammered into well compacted gravel that was likely 2 or 3 feet thick. No idea if a load test would give you similar results. But it would at least let you know if it's even in the range of possibility.

Please note that is a "v" (as in Violin) not a "y".

 

[Trillers]

WinelandV,

We are in the same situation with a very similar scenario. Well-compacted gravel (5,490# compressive strength), 20" thick.

The forms use #5 rebar in the same fashion as the pin you described. Just was never able to figure out how to calculate the shear capacity and pullout resistance.

But just as with your case - it works.

Thanks for the info.