SELECTED METHODS OF TESTING HYDROGEOLOGICAL FEATURES OF ROCKS AS A SUPPORT FOR GROUNDWATER FLOW MODELLING NEAR A RECLAIMED OPEN PIT

An appropriate method of depositing post-mining waste can impede very significantly the water flow within the landfill and be one of the most effective methods of limiting the leaching of pollutants and their migration to the aquifer. The forecasting of water circulation and the dynamics of the process of pollutants leaching and their migration is supported by numerical modelling programs that allow assessing real conditions to follow changes in the processes over time. In case of reclamation of an open pit with post-mining wastes from hard coal mines, model research for the assessment of its impact on the aquatic environment should be supported by a complex of modern, uniform and mutually complementary methods of testing rock materials. The numerical models of groundwater flow and migration of pollutants required, among others, data on hydrogeological properties of rocks deposited in a storage site. They are based on both the results of field and laboratory tests. An important element in forecasting the impact of post-mining waste used in the reclamation of an open pit on groundwater is the quantitative assessment of the absorptive capacity of deposited wastes (mainly Carboniferous rocks) and the volume of free spaces of rock debris as a zone particularly susceptible to mineral weathering and pollution leaching. These tests must be carried out simultaneously with the simulation, in the laboratory, of changes in the filtration coefficient of loose materials depending on the thickness of the dump and changes in the vertical pressure exerted by rocks filled up during reclamation. Based on the example of research conducted on the material stored in the excavation after exploitation of backfilling sand, the authors proposed to adapt the research methods originally developed for the purposes of forecasting water hazards in mine shafts and underground excavations for the need of assessing changes in water circulation conditions within the dump.