Topographic Influence of Longwall Mining on Ground‐Water Supplies

The extent of potential aquifer dewatering resulting from underground longwall mining is determined through application of a nonlinear finite‐element model. The model represents the form of the body strain field that accompanies mining‐induced subsidence, and uses strain magnitudes to define the modified hydraulic conductivity field. The model is applied to test the sensitivity of the induced strain field to ground surface topography. The location and extent of three characteristic zones of conductivity enhancement are defined, representing gravitational detachment above the panel, shear failure above the abutment, and extensile deformation at the ground surface. Correspondingly, well completion locations are ranked with their potential for dewatering representing relatively high potential in upland areas and relatively low potential in valley base locations. These results amplify and offer a phenomenological explanation of observational data. Modeling results are compared with several documented studies in the Appalachian coal fields and favorable agreement achieved.