Stresses in the immediate stone roof of a coal mine roadway
An analytical approach to designing roof support needs a model that quantifies the magnitude of the stresses acting in the immediate roof. There is a large amount of measurement data on stresses above pillars but few models for the stresses within the bolting horizon. Very small roof deflections result in substantial relaxation of horizontal stresses in the immediate roof. Increased vertical and horizontal stresses at the maingate increase the height of compressive failure and hence the “softened zone” and this leads to greater loading on the bolted roof beam. The situation does not change in a material way at the tailgate unless there is major yielding of the side of the roadway in which case the horizontal stresses in the roof line may become tensile.