Instead of digging deep and pouring cement,the Diamond Pier is a cementious block with 4 sockets set at angles. Long steel pipes are driven into the soil through the sockets,pinning the block in place,preventing frost heave.
No digging needed,super cool.
Of course I want to do it on the cheap.
Well, at least steal some of the principles.
In particular, I can see digging a about hole 2' wide 1 deep,and inside that hole driving four sticks of #5 or 6 rebar equidistance around the perimeter.
A hammer drill with a ground rod driving bit would be ideal for this.
The rebar would be driven about 5' deep at 45° angles,
The concrete is then poured,with provisions made for tying in a post or pier.
Rebar is meant to be encased in concrete. Rebar sent into the ground will RUST away. That is why the diamond ones use a high grade steel instead to slow the decay of the pins. Do rethink about using rebar for a 'permanent' structure.
I suspect a lot of the holding force of the Dry Diamond comes from having rigid piles, such that the upward frost-heaving forces are balanced by the 45˚ angle and friction of the soil resulting from force-driven piles (you need something stiff to drive it into the ground). I suspect you may run into a problem using rebar for this since it's very much not rigid (it's designed to flex and stretch in tension). The ribs on rebar will also reduce the soil friction since they will bore out a hole larger than the rebar itself (the ribs are designed to add grip to liquid concrete, which fills in between those ribs). If you opt for some iron pipes (maybe filled with gravel/concrete) or t-bars rather than rebar, I think that could work well. It's an interesting idea!
I kind of disagree with the rebar statements only because at home centers you get the cheap non-coated rebar, but real rebar that is used in any kind of Federal or State road work is coated with epoxy. Not only would it be longer lasting, it would be easier to drive into the soil from its slipperiness. It should be very easy to source.
As far as strength, I disagree with that as well as I think the angle is far more important then strength. I know this because one time I had a full bloodied bull that I tethered into a pasture. What I did was take a piece of flat bar 4 inches wide, a quarter inch thick about a foot long. Then I welded the same flat bar at an upwards angle on each side of it. At the top I welded a swivel to attach the lead that tethered him. It was quick, easy and out of A-36 steel...mild steel. That 2000 pound bull would take off on a tear, run about 100 feet then practically be slammed to the ground by that rope checking him. What it was was those angled pieces driving into the ground that kept the deadman from pulling out of the ground. It was unbelievable how defective, small and cheap it was which was exactly why I used it...no fencing to buy! When he grazed all the grass, I just hooked the deadman to my tractor, hoisted it out of the ground, then dug another hole where the bull could graze on fresh pasture. Man it worked slick.
BTW: The swivel was just so that dug down to ground level, the rope had nothing to wrap up into as the bull grazed in his circle.
I have about 15,000 30" pieces of leftover federal road project greenish coated rebar that I won off an auction for $100. (they punched a chunk of the Port to Plains road past here) I use it for all sorts of things. It is more resistant than regular rebar but still knicks up and otherwise will instantly RUST just like the stuff at the home center. They are complete at that length and both ends are coated. 30" isn't enough to hold a pier, I think.
Companion Planting Guide by World Permaculture Association