Assessment of numerical modeling techniques for groundwater flow into longwall mines

The coal mining industry in the United States has an extensive history of multiple seam mining, where operations start development in seams underlying abandoned, flooded workings. Development or full panel extraction under such conditions can present hazards such as inundation of mine workings and will require additional mitigation efforts. This paper discusses the application of numerical modeling to assess the impacts of mining under bodies of water, focusing on multiple seam mining. Fractures induced by mining, naturally occurring faults, and other voids in the rock strata can create pathways for water flow. Reliable prediction of mining-induced water flow paths requires the estimation of interburden strata permeability pre- and post-mining. The hydraulic conductivity of the interburden strata can be measured directly in the field with packer testing, piezometric monitoring, etc., or estimated from laboratory analysis/tests with core and geophysical logging.