Testing the in situ Bulk Density of MiningWaste Stored in Dumping Grounds

Abstract

More than 200 dumps serving the disposal of waste produced by hard coal mines are situated in the Upper Silesian region. The material found in the dumps is mainly coal mining waste (i.e., overburden rocks obtained in the production and processing of hard coal). Volumetric and bulk densities are important physical parameters when it comes to recording the amount of waste disposed at the dumps. A possibility of determining this parameter during field studies was analysed. The method applied consisted of excavations performed in dump areas, weighing the excavated material and a precise determination of the volume of a selected space. A study carried out in this way allowed for testing a much larger sample, as the mass of the sample was only limited by the carrying capacity of the vehicle transporting the material to be weighed using industrial-grade scales. This had a positive impact on the accuracy of determining density. The precise determination of density was achieved by using the photogrammetric method, which guaranteed high accuracy. Two alternative photogrammetric techniques were used to ensure the control of calculations, i.e., close range terrestrial photogrammetry and low-altitude photogrammetry using unmanned aerial vehicles. Photographic equipment with high-resolution matrices was used. The processing of photographic documentation was conducted using professional software: Pix4d Mapper and AutoCad Civil 3D. Based on the mass and volume results obtained using the method described above, the bulk density of three coal mining waste samples was obtained for the actual conditions of the dump. The in-situ testing allowed us to consider the actual density of the waste material found in the dump.