Designing for upper seam stability in multi-seam mining

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Virginia Polytechnic Institute and State University


The problem of interaction resulting from mining seams above a previously mined seam has been thoroughly investigated in order to develop and evaluate methods of improving upper seam ground conditions when mining through either active or passive subsidence waves. Design criteria have been developed based on results from case studies, statistical analyses, geological characterizations, numerical studies, and physical modeling. These include identification of critical factors, prediction of the location and magnitude of potential interaction areas, and remedial options.

Complete design procedures have been devised which include five essential steps: data collection and mapping, classification of mining conditions, characterization of strata, preliminary evaluations, and stability analyses.

The methods developed for interaction analysis are classified into two categories: qualitative and quantitative. Qualitative methods can be used for a preliminary evaluation using rules of thumb and empirical formulas developed from statistical analyses. Quantitative methods involve more detailed stress and strain computations based on quantified interaction mechanisms. These mechanisms include trough subsidence, load transfer, pressure arch, large scale caving and fracturing, and interseam failure. Finally, in order to expedite the transfer of research findings to the field for application, an interactive and comprehensive computer program has been developed which incorporates all possible interaction mechanisms and aspects of the design and evaluation process for multi-seam mining.