A new method of analysis of water‐level response to a moving boundary of a longwall mine

Abstract

Longwall coal mining is an economical method for coal extraction that allows most of the coal to be extracted from a wide rectangular panel. The roof of the working face area is temporarily held up by supports which advance as the mine face advances. A basin‐like subsidence trough develops at the ground surface over the panel as the panel roof behind the supports collapses. A dynamic subsidence front causes a water‐level drop at wells ahead of the panel. We examine the effects of subsidence on water‐level by introducing a sink that moves with the mining face, using the one‐dimensional flow equation. To test the validity of this method, we estimated aquifer parameters of Trivoli Sandstone aquifer over a longwall coal mine in the Illinois Basin by analyzing water‐level versus time data measured from three observation wells. The presented method predicts a value of transmissivity and storage coefficient that is reasonably close to the average of pumping test results. With this method we provide solutions to two significant problems: (1) Presubs(2) water‐level drops can be predicted for a planned longwall mine if the aquifer parameters are known.