Update - 21 Feb 2021
Particle simulations are mainly used in this scene. Some of them are controlled with the velocity volume inherited from pyro simulations. Also, I combined RBD solver and pop solver to create the motion for the orange small triangle fractures.
Update - 13 Feb 2021
The sand is generated with vellum grains. They are classified into groups of the chunk so that they look like wet sand. In the post process, I picked out some vellum particles and replaced them with small stones that have variations in shape and size.
There are two kinds of trash; plastic debris and electric wires. Both of them are generated procedurally, which means those shapes and sizes are varied automatically. They are handled by vellum cloth and hair simulation.
I created three types of scrap metals; boards, bars, and tires. Boards and bars are bent randomly so that they look like more scrap. Tires have two variations; wheel and tire, or wheel only.
In the RBD simulation of these scraps, the result of the sand simulation is used as colliders. If all of those vellum particles were treated as static objects, rigid bodies would be a messier result. Therefore the particles that went not so far from their rest position are only handled as colliders, while the other particles are ignored.