Impact of the Hydrogeological Conditions on the Calculated Surface Uplift above Abandoned and Flooded Coal Mines

Abstract

Upward surface movement or uplift has been extensively observed above abandoned and flooded deep coal mines, which used the longwall mining method, i.e., a caving method. Detailed analysis of satellite measurements indicated that the process of uplift is one of the more complex phenomena in ground control. The observed uplift is linked to the flooding of the underground infrastructure and rock mass. This was confirmed by conducting analytical calculations. The distribution of water pressure at the end of the mining phase and their increase during the flooding is an important aspect in all estimations. The main objectives of the study are to compare the impact of various hydrogeological conditions of this distribution at the start of the flooding phase and to select the most realistic one. They range from a zero-water pressure to a linear decrease from the top to the bottom longwall panel. Different scenarios of how the water pressures change as a function of time are also compared, i.e., from filling an open reservoir from bottom to top, to a systematic change in the linear downward trend. The main conclusion is that a linear trend, i.e., the original assumed scenario, is the best option in comparison to the other scenarios evaluated. It provides the best fit between the estimated uplift values and the large amount of remote sensing measurements along north–south transects in the Belgian Campine coal basin.