Mechanics of interseam failure in multiple horizon mining

Abstract

The mechanics of massive interseam failure in a multiple seam mine was investigated using three approaches: case studies, physical models and computer analysis. Specific examples of multi-seam mines with the underlying seam mined first prior to the mining of the overlying seam were studied with some design guidelines drawn from them. A loading frame capable of testing model blocks of 24 inches by 24 inches by 6 inches and also capable of applying up to a maximum of 10,000 psi of pressure on the models was designed and built. In this investigation, factors that affect the stability of the overlying seam when the underlying seam is mined first were studied using the finite element method and the Mohr-Coulomb failure criteria. Critical failure surfaces obtained from the computer analysis were analyzed for columnized and staggered pillars in room and pillar mining with the columnized pillars favored over the staggered ones.