This article presents the results of the study of changes in mineral and chemical composition of artificial aggregates consisting of coal shale (a hard coal mining waste) and fluidized ashes. Such an aggregate was used for road construction. After completion of the construction works but before making the road available for public use, significant deformation of the surface in the form of irregular buckling of the asphalt layer occurred. It was excluded that this resulted from mining damage, design errors or performance mistakes, among others. A study of the materials that had been incorporated in the construction layers was undertaken in order to find the component and the mechanism responsible for the buckling of the road surface. A comparison of the mineral and chemical composition of aggregate samples collected from the embankment where the road buckled with the reference sample and samples from places without deformations showed that the bumps in the road embankment consisted of minerals that were not initially present in the aggregate. Wastes produced as a result of high temperatures (slag and power plants ashes, metallurgical wastes) are not as stable in terms of chemical and phase composition in the hypergenic environment. As a result of the processes occurring in the road embankment, anhydrite, which is the primary component of fluidized ashes, was transformed into gypsum and ettringite. As a result of contact with water CaO (present in fluidized ashes) easily changed into calcium hydroxide. As the crystallization of these minerals is expansive, it resulted in the filling of pores and, in extreme cases, in a substantial increase in the volume of the aggregate and, consequently, in the deformation of the road surface.

Post-mining dumps are a common sight in the industrial areas of Silesia (Poland). Despite several reclamation projects, many of them still constitute an unresolved problem. It is not only a matter of unaesthetic view – they often pose a threat to the environment and the people living nearby. Despite revitalization, some dumps are not properly maintained and are at the risk of slope failure. Such places require constant geodetic observation and stability control. In this article, the example of a dump located in the city of Gliwice was used to show the possibilities offered by the use of photogrammetry and unmanned aerial vehicles (UAV) for cyclic checks of the embankment condition. The current state of the dump and the results of interventions after two incidents of slope failure,were observed. The main slopes of the terrain surface and at the selected cross-sections were determined in two flight missions. The obtained geometrical data were used in the further numerical analysis. Finite Element Method model representing one of the escarpment cross-sectionswas built to estimate the factor of safety and determine the main mechanisms responsible for the failure. Elastic-perfectly plastic Coulomb-Mohr model was used to describe the behaviour of the minestone and the ‘ c – tan φ reduction’ – for calculation of the stability. The problem of reliable material properties’ estimation was emphasized. The analysis included the impact of seepage and total head difference on the slope stability. It was concluded that the rainfall intensity had a decisive influence on the instability of the dump.