MODEL RESEARCH ON THE EFFECTIVENESS OF TECHNICAL METHODS OF LIMITING THE EXPANSION OF THE DEPRESSION CONE CAUSED BY DEWATERING OF THE PLANNED GUBIN OPEN-PIT BROWN COAL MINE

Due to the planned exploitation of the Gubin lignite deposit by opencast method, a numerical hydrogeological model was built. The main goal of the model was to forecast the development of the cone of depression caused by the future mine dewatering. Due to the location of the mine near the Nysa Łużycka River, a drainage system will be developed. The main task of this system is to eliminate the development of the cone of depression in the upper Quaternary aquifer in Germany, as well as to protect the Natura 2000 areas located in the immediate vicinity of the mine against harmful effects on groundwater-dependent ecosystems. The modelling studies allowed analyzing the efficiency of slurry walls, deep barriers of recharge wells, and shallow soakaway systems for water from the future mine dewatering. It has been shown that in case of dewatering of a multi-layer aquifer complex with many hydraulic contacts, the use of slurry walls may be insufficient to limit the development of the cone of depression. However, the combination of slurry walls with the systems recharging the aquifers enables effective counteracting the negative impact of dewatering on the environment.