uplift pressures in concrete walls

[MrBennett]

Hello, I have a problem that I hope someone here is able to help with.
I am doing a 2' concrete wall. 9' tall if that matters. I have to install a trench in the middle of the wall that is 2' deep and 8" wide. It runs the length of the wall. What I need to find out is this, how much up lift is the concrete going to put on this trench form and want to make it rise out of the wall? I have it hanging from plywood spreaders. But that is just holding it up. How do I keep it from coming up as I place the concrete around it?
Thanks

 

[civilperson]

2 feet deep trench has zero uplift at the top and 300 pounds per square foot at the bottom. Use an average of 150 pounds per square foot or 200 pounds of uplift per linear foot, (2 feet deep x 8 inches wide x one foot length x 150 pounds per cubic foot). Try lots of nails and two bys for hold downs.
If the top 2 feet of concrete is placed very slowly in level lifts, the uplift force will be minimized to the depth of the plastic mix. I suggest no more than one vertical foot of placement per hour with normal mix design.

 

[MrBennett]

Thanks, that is just what we came up with also. Glad to get another opinion to confirm.