I have never seen this process before, but I know a few few things from working clay over the years. I used to have students bring in a coffee can of "dirt" from their yard or where ever they going get it. One process in refining clay is to add lots of water to make a slurry. Dump some of the dirty into a 5 gallon plastic bucket. Add water then use a drywall mud mixer to or similar. Poured down a low sloped chute, the heavy material(gravel and sand) will fall out quickly. The remaining particles "sort" themselves by size, with lighter particles (topsoil, silt,etc,) flowing out the end. Most of the stuff in the middle was clay. Then you let the clay dry to the point you can use it.

That machinery reminds me of that process, starts with a slurry, gets drier, with each step. Being "dumped on the ground" may have been the last step before a loader picked it up to dump it into a hopper for extruding into products, (bricks, tiles, etc) or packaging for sale.

My guess