During the construction of tunnels using tunnel-boring machines (TBMs), the wear of disc cutters is an unavoidable process. The timely replacement of worn disc cutters can have a positive effect on construction time and therefore on costs. The wear of disc cutters can be assessed using various measurement methods. The aim of this article is to show different methods of measuring and evaluating the wear of disc cutters and to present their main advantages and disadvantages. In this study, four different wear-measuring methods were used and applied to a worn double disc cutter: a macroscopic visual inspection, profile measurement with a caliper, weighing, and close-range photogrammetry. The results of the measurements showed that the worn disc cutter was subject to normal abrasive wear, with local steel chipping occurring. Based on the close-range photogrammetry measurements, a profile of the worn disc cutter was also created and compared with the original profile. It was found that the best results for the wear assessment of a disc cutter can be achieved by using several measurement methods simultaneously. The integration of different measurement and evaluation methods is therefore recommended for a comprehensive understanding of disc cutter wear.

Roller cone drill bits are used in drilling larger diameter wells. The drilling efficiency of the roller cone drill bit depends on the wear rate of the materials that forms bit teeth, which crushes the rock at the bottom of the well. To prevent excessive wear, research has largely focused on the study and determination of abrasion-resistant materials. In our work, we investigated the wear mechanism of a roller cone drill bit whose wear-resistant teeth are protected by a hard metal coating welded onto the teeth. The difference between material properties of erosion-protective carbide coating and the tooth steel leads to uneven wear of bit teeth. In order to determine the material changes, we carried out detailed studies of the rock through which drilling was carried out, the drilling parameters and the materials of which the roller cone bit is made. The principle of wear of the tooth materials and their carbide coating, determined by our research, indicated the guidelines which could be basis for the development of abrasion-resistant materials could be carried out, as well as the problem of applying an erosion protection to the teeth of the studied type of roller cone bits.

In geotechnology and mining, tools and equipment interact with aggressive geological material, causing the wear of these components. For this reason, it is important to determine the rate of abrasivity of individual geological materials, depending on the type of interaction with the tool. Various abrasivity tests have been developed in laboratories. Some of them are general, while others are special. What they all have in common is that they attempt to determine the abrasivity of rocks or soils in relation to the wear of the test specimens. This article gives an overview of the laboratory test methods for assessing the abrasivity of geological materials, which are useful in the field of geotechnology and mining engineering. General and special abrasivity tests are presented in detail. The aim of the article is to present existing laboratory tests to assess the abrasivity of rocks and soils, based on which further investigations of wear can be considered as part of a comprehensive approach to this tribological problem. Understanding of the wear mechanisms is the basis for the development of wear-resistant tools and models for predicting the tool life.

The basis for the safe extraction of mineral resources underground is good knowledge of the local and surrounding geological conditions and the activity of the nearby aquifers. Hydrogeological modelling in combination with dewatering of the aquifers above the coal and monitoring of the groundwater level in piezometers is of particular importance for safe underground coal mining in the Velenje mine. This study shows the contribution of an improved hydrogeological conceptual model to the prediction of groundwater movement in the aquifers above the coal seam using a hydrodynamic six-layer model. The improved hydrogeological conceptual model is based on the determination of the groundwater age and a detailed geological classification of the layers. The groundwater ages, determined using the tritium detection method, were important to understand the recharge of the individual aquifers. As there is no direct recharge at the surface, the aquifers are only recharged by the slow leakage of groundwater from the upper to the lower aquifers. The hydrodynamic six-layer model, which is based on an improved hydrogeological conceptual model, now simulates groundwater more accurately than previous hydrodynamic models and helps with dewatering planning and the technical design of mining facilities near aquifers.

In this paper, research on the possibilities of sodium sulphate (Na₂SO₄) separation from other substances in the filter ash sample is presented. The research material contains six components that differ in chemical composition and density. The possibilities of Na₂SO₄ separation using dry and wet methods were studied. The dry method was based on separation with a centrifugal air classifier at four cut size limits. The wet method was based on the dissolution of water-soluble components, filtration of insoluble components, and drying the products. The sulphur content of the individual products was determined using both methods. The aim of the research was to determine which method is more suitable for separation of the material in a way that most of the material would contain as little sulphur as possible and the rest of the material would contain concentrated sulphur. The wet method proved to be more successful. The product with mass fraction 33.1% of the total mass, obtained from the aqueous solution, contained 8.39% sulphur after filtration and drying. The water-insoluble component, with mass fraction 66.9% of the total mass, contained 0.56% sulphur. The dry method with the centrifugal air classifier proved to be less successful in comparison with the wet method. The particles containing Na₂SO₄ are very similar in size and density to the other components of the material, so the separation to the desired extent was not achieved.