Hydrogeological and physico-mechanical responses of physically heterogeneous waste rock to storage time and vertical pressure

The variability of the selected properties of mining waste under the influence of its long-term storage and increasing vertical pressure is assessed, through tests conducted on five samples of waste rock used in the reclamation of an open-pit mine. It was found that the considerable variability in the mining waste grain size, exhibiting extreme strength and slakeability parameter values, influences the filtration properties of the rock material. Increasing vertical pressure exerted under laboratory conditions resulted in significant grain degradation, material consolidation and permeability reduction. Exponential functions are the most accurate way of characterising the correlations between the rock sample volume density and the filtration coefficient. The test results demonstrated that the oldest waste was characterised by the lowest permeability and highest compressibility. The material with half a year storage time exhibited the highest filtration properties. Waste stored for 15 years and subjected to coal recovery was also characterised by high permeability. The mining waste filtration coefficients obtained for each vertical pressure value were referenced to values characteristic for soil and rock at a water temperature of 10°C (the average annual temperature of shallow groundwater in the area of waste sampling for laboratory testing).