Catherine Windrose wrote:While looking for ways to test different mixes with or without added materials, I found this video which gave me a lot of ideas how to test at home.
Sand Castle Holds Up A Car! - Mechanically Stabilized Earth
When I was thinking about using sandy soil in earthbags and didn't want to risk wearing and tearing, I looked for screen materials as mentioned after the 4:00 minute mark in the video above. (That homework led to finding basalt materials formed as rebar, mesh, fabric, rope for various purposes. I may use a basalt mesh or fabric for a project.)
Your area being low in clay, might produce the effect you're looking for by making a thicker wall by layering something suitable about every foot or two. If you try dropping different shapes of heavy weights on the test bricks, that might help find a way to combine materials to achieve the strength you're looking for.
Forgive the lack of tech jargon. I'm nowhere near being an engineer, and learn by seeing what goes boom or not :)