Buriable concrete ducts for underground belts
We could build some undergroud pipes with some digging, then what about the belts? To protect our product from crunchy soil, there should be a little shielding, like a pipe for flowing belts. Soild concrete duct.
This design might be little annoying when bending the belts into the duct, but with couple of conveyor lifts which will be available soon, there will be no problem with the ends of the tunnel.
Plus, if we make it to be stackable, the ducts could also be used as bridges over some gaps, like a depleted mine.