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.

The dynamic replacement columns are formed by driving a coarse-grained material into a soft soil by means of repeatable drops of a pounder. The final shapes of the columns are non-cylindrical and depend on the subsoil conditions. This paper presents results of the laboratory study on influence of the thickness of the soft soil on the displacements of the backfill aggregate during the driving process. A test box with one acrylic-glass wall was prepared, in which, over a load-bearing sand layer, a soft soil of various thicknesses (���� = 0.3, 0.4 or 0.5 m) was modelled using a semi-transparent acrylic polymer. The displacements of the backfill gravel particles were tracked by means of a high-speed camera. The material was driven by dropping a 0.2 m high (����) pounder. The results revealed that the distance between the bottom of the first crater and the top of the sand layer played an important role in directing the particles. At ����/���� = 2.5 pear-shaped floating columns were formed as the grains in the side zones were less affected by the pounder drops and their paths deviated from the vertical axis by not more than 50°. In case of ����/���� = 2.0 and 1.5, the column bases reached the bearing layer and the impact energy caused much larger vertical and horizontal displacements of the backfill material in the side zones – the observed largest angles were equal to 64° and even 90°, respectively. Eventually, the final column shapes resembled a non-symmetrical barrel and a truncated cone.