The basic structural unit that we used was a stack of 25-30 5 gallon buckets. The widest part of the bucket is ~1 foot in diameter and a stack buried 3-4 feet in the ground is around 7 feet high. Each stack, once wrapped in wire and stuccoed, is very stiff but obviously has a tendency to fall over. Therefore the only real problem in designing the wall was lateral strength.
Earlier parts of the wall were stuccoed like this but after completion it was decided that the wire and stucco did not add enough lateral stiffness.
The stacks are buried in a 1 foot wide X 3-4 feet deep trench and tamped into place.
The already completed portions of wall had a single stack added perpendicular to the wall every 5-10 feet as a buttress.
The buttress's used up extra space so internal piers were developed to stabilize the stacks. Every 5-10 feet two thirds of the buckets in a stack had the bottoms cut out and (stacked as usual) were used as forms for these piers. The piers extend from the bottom of the trench to 3 feet above the ground.
The stucco was anchored with a range of recycled wire meshes (chain link fencing, chicken wire, rebar, remesh, and even some stucco wire). You can see more on the Photo page.
Where required this mesh was "sewn" to the stack using wire threaded between the stacks.
Where the buckets taper at the top of each stack, the bucket lids were placed (held in place by the stucco wire and stucco) as a filler to minimize the amount of stucco required. The lids were also used on the top of each stack to flatten out the top of the wall and adjust for dips in the ground or trench.