This is a set of 4 Substance Designer made SBSAR materials available for use in a number of programs like Substance Painter, Unreal, Marmoset Toolbag and Unity.
These materials have many options including the colors, rock and grass amounts, footprints, water build-up and more.
For more images and video check these:
Mud - https://www.artstation.com/artwork/8xJon
Dirt - https://www.artstation.com/artwork/q13Oy
Dirt Wall - https://www.artstation.com/artwork/zy1l6
Rock Wall - https://www.artstation.com/artwork/9JqPo