We have old and new mining operations and leftovers from it in our region. Next to a new highway system of toll roads are what is called slag piles or slate dumps. They are hills that go up hundreds of feet that are made of what comes out of the coal mines that is not coal. It is largely slate that is mixed in with a little dirt. New code requirements decide how these little mountains are made, but we have a lot of old ones here. I found myself reading an LPILE manual to learn how the software works that can estimate the stability of our hills made of slate and dirt.
The reason this is so important is that we have seen these hills collapse. There is a slide just down the road from our home where a slate dump was added to by tons of dirt when the toll road went through. The dirt on top acted as a shear force on the slate below and it slid. The potential for these slides could case danger to surrounding homes as well as the collapse of some roadways that were built through areas that were once slate dumps and slag piles. The slate and slag does not have the lateral strength of dirt. You can compress it a lot, but a sideways force makes it slip.
The LPILE software shows us what we need to do to strengthen at risk areas. We have designated some areas as ecologically unstable. That means that people are not even allowed to walk in the areas. It is tough to enforce as locals use the hills for motorcycles, quads and four-wheel drive outings as well as for equestrian use. Local fire departments use them to teach high-angle rescue classes. The software helped us know how to use inserted reinforcement rods to provide stability and what to plant on top to minimize slips and slides.