Properties Of Immediate Above Seam Strata And Their Relationship To Ground Control At San Juan Mine

摘要

The physical, structural, and depositional features of the immediate above seam strata which characterize San Juan Mine are localized in extent; regional scale features having little direct influence. Four primary drivers of ground control difficulties associated with the immediate above seam strata are geomechanical properties, structural features, sandstone channels, and water. The immediate above seam strata are characteristically weak with limited load bearing capacity. Structural features, primarily faults and to a lesser extent weak bedding planes and contacts, present planes of weakness within the strata allowing for displacement. Sandstone channels are associated with higher densities of faults due to compactional shear and are the primary source of mine roof water. Mine roof water has a detrimental effect on the strength of the immediate roof mudstones as well as through degradation of roof support through chemical interaction.