Type-curve analysis of water-level changes induced by a longwall mine

Subsidence due to longwall mining creates long-term environmental effects, such as alteration of surface drainage patterns, changes in aquifer characteristics, and water-level drops in wells near the mine panel. Evaluating the impact of longwall mining on groundwater resources requires a knowledge of aquifer properties, both in front of, and behind, the mining face. In this study, we develop a method based on the one-dimensional flow equation, and utilize type-curves to estimate an aquifer hydraulic diffusivity value from water level versus time measurements at a single well. We tested the method by calculating the hydraulic diffusivity value of the Trivoli Sandstone aquifer over a longwall coal mine in the Illinois Basin, and our results are reasonably close to reported values. The presented method significantly reduces the computational effort involved in: (1) predicting mine-induced water-level drops, and (2) determining the hydraulic conductivity and storage coefficient value representative of a larger aquifer volume, as compared to conventional aquifer test methods.