Among the main directions of works on energy acquisition, there is the development and application of the technology of underground gasification of coal deposits (UCG). During the process of deposit burning and oxidation, there is also impact of temperatures exceeding 1000°C on rocks surrounding the deposit. As a result of subjecting carboniferous rocks to high temperatures for a prolonged period of time, their structure will change, which in turn will result in the change of their physical properties. Due to the project of underground coal gasification, as performed in Poland, laboratory tests are currently under way to a broad extent, including physical properties of carboniferous rocks subjected to high temperatures. The article presents results of laboratory tests of rocks surrounding the designed geo-reactor: changes to bulk density, specific density and porosity due to high temperature, and confronts the above results with the results of tests of thermal conductivity, specific heat and heat diffusivity (temperature conductivity) of the rocks. The mineralogical investigations were presented too.

One of the most important elements of road construction is its substructure, which constitutes the base on which the next layers of road are placed. Mixture of crushed-stone aggregate is very often used as material for substructure. The most frequently used type of aggregate is magma rocks, due to its good physical-mechanical properties. However, it is not always available, so it is substituted by sandstone or even concrete rubble aggregates. The bearing ratio CBR is a parameter determining the suitability of a certain aggregate for road substructure. It is also one of the most popular quality tests of aggregate as it does not require complex apparatus. This paper analyses the results of physical and geotechnical tests with particular focus on CBR bearing ratio of crushed aggregates and their application as substructure for road construction. There has also been an attempt to find the correlation between CBR bearing ratio and other physical and geometrical properties.

Each excavation or excavation complex intended to be backfilled or secured requires an individual approach, and conducting a detailed geomechanical analysis which will allow the selection of the appropriate manner of securing or backfilling or liquidation, and the order of performing mining works. The numerical model of the selected chamber or group of chambers must accurately reflect the reality and have an appropriately selected calculation model. The paper presents the selected aspects of numerical modelling of the “Wieliczka” salt rock mass. There are method of selection of geotechnical and rheological parameters of salt, the geometrization of the excavations continues and selection calculation model.

As a result, of more than 700 years of exploitation in the Wieliczka Salt Mine, a network of underground workings spreading over eleven levels was created. All mine workings of significant historic and natural qualities and the majority of functional mine workings designated to be preserved are located on levels I to V. The most precious of them, available to tourists, are located in the central part of the Mine on levels I-III. The Mine is not anticipating to make levels IV, Kołobrzeg and V available for a wider range of visitors, even though there are historically and naturally precious workings in those areas as well. The most valuable of the mine workings come from the eighteenth and nineteenth centuries and were exploited mainly in a bed of fore-shaft salt, Spiza salt and the oldest ones. The characteristic feature of these excavations, distinguish them from the chambers located on the levels I-III, is the room-and-pillar system that had been used there. Mine workings exploited in this system measure up to 100 metres in length, and the unsupported pillars standing between the chambers measuring 4-10 metres in width were remained. The described above levels, including levels of VI-IX are to provide a stable support for the workings located higher up. The remaining part of the mine, with the exception of the function workings, is designated for liquidation by backfilling. The article presents an assessment of stability of the mine workings, located on levels IV-V, and their impact on the surrounding rock mass and the land surface. The analysis was based on geodetic measurements and numerical calculations for strain state of rock mass surrounding the mine workings, in actual conditions and after partial backfilling, and forecast of the rock stability factor after the end of backfilling. The assessment stability factor in the vicinity of excavations at levels IV-V was based on the results of spatial numerical analysis covering the entire central area of the mine from the surface to level V. Numerical calculations were performed using FLAC programme based on the finite difference method, allowing to observe the mechanisms and processes of destruction and deformation. The calculations were performed for the elastic-plastic medium with the Mohr-Coulomb failure criterium. The choice of this computational model was dictated by a very diverse geological structure of the Wieliczka rock mass and a complex system of excavations.

The basic tests that allow the mechanical properties of grained material to be evaluated are tests of an aggregate’s resistance to crushing - the Los Angeles coefficient, and resistance to abrasion - the micro-Deval coefficient. These parameters primarily depend on the physical and mechanical properties of the raw material from which they are produced. The available literature widely describes the relationship between these parameters and bulk density, porosity, ultrasonic wave velocity, compression strength, tensile strength and point strength. This paper presents the relationship between the mechanical properties of aggregates and their geometrical properties. The analysis was carried out for the relationship between the Los Angeles and micro- Deval coefficients and the flatness and shape indices. As a result of the conducted considerations, the influence of the aggregate assortment on the analysed coefficients was also noted. All of the tests were carried out for aggregates (arch stones and mixtures) produced from sandstones from the Magura, Cergo and Krosno layers.