Pond Wall Decisions

[bstethem]

I am looking for some (free) advice in my DIY koi pond project. I am building a formal pond approximately 16' X 22' with a max. depth of 5'. The excavation will be 3' deep so 3' will be backfilled and 2' will be above grade all around. I am interested in ICFs, insulated concrete forms intended for basement wall construction. The one I am looking at (Super-Forms) has 6 7/8" thick internal cavity and there are provisions for re-bar to clip in. They recommend 3500 psi concrete be pumped in these forms and claim a 30% strength increase due to slower cure times. My "idea" is to dig and pour a footing below the frost line, pour 5' high walls using the ICFs, and drop in an EDPM (rubber sheet) pond liner and fill with water. My "question" is how can I figure if this type of construction will stand up to the hydraulic pressures of 5' of water? Suggested re-bar size/placement. Other reinforcements? Is this even advisable? The use of these forms will save me considerable $ as I can do most of the work myself. Any thoughts???

 

[ishvaaag]

As long as you think in providing inner impermeabilization with a membrane, only your reinforcement (mechanical strength) problem stands. Then you have I assume some slab at bottom and some prefabricated forms to infill.

Since the size of your construction is so small, almost any practical reinforcement should stand, as long there's continuity between the sides and bottom. Whatever the way you construct this box, the calculation may be made either by a 3D model of the box or far simpler as we all do as a 2D model of the section of your cantilever wall. It is unlikely that earth pressures control since you will have the pond standing 2 feet over the ground level. So you have service level 0.75 m·ton/m, assume 6 inch arm, force is per meter 1 ton/m service level. This thing I most likely would reinforce with passive reabar about #2 or 3 every 6 inch square, both sides, ensuring no less than 1 foot overlap with same rebar coming from slab (maybe same reinforcement) at bottom. Ensure in every direction this is more in total (sum of both faces) more than 4/1000 of the section horizontally for walls and 1.2/1000 vertically (walls), and 2/1000 of the section for the slab.

Put L shaped rebar at corners to unite horizontal rebars

Forget psotension, passive rebar is enough.