Inc. His clients include about 100 mining companies. Mr. Parker has worked in several hundred mines. He is frequently called to help solve an unexpected problem, like a roof-fall. The roofs were broken and supported by roof bolts, which were themselves breaking regularly and requiring continual replacement. The material continually moves plastically.
Vertical pressure induces sideways pressure.
The salt is behaving like a fluid and flows towards zones of lowest pressure. This term is usually applied to more brittle material, but rock salt will do the same thing where it is not confined. A failed roof could be supported artificially, but if not supported it will fall. In Panel 1 there is already roof failure. The supports mask the failure, but one can see shear along the ribs, cracks, and joints in the ceilings.