A variety of geophysical methods and analytical modeling are applied to determine the rockburst hazard in Polish coal mines. In particularly unfavorable local conditions, seismic profiling, active/passive seismic tomography, as well as analytical state of stress calculating methods are recommended. They are helpful in verifying the reliability of rockburst hazard forecasts. In the article, the combined analysis of the state of stress determined by active seismic tomography and analytical modeling was conducted taking into account the relationship between the location of stress concentration zones and the level of rockburst hazard. A longwall panel in the coal seam 501 at a depth of ca.700 m in one of the hard coal mines operating in the Upper Silesian Coal Basin was a subject of the analysis. The seismic tomography was applied for the reconstruction of P-wave velocity fields. The analytical modeling was used to calculate the vertical stress states basing on classical solutions offered by rock mechanics. The variability of the P-wave velocity field and location of seismic anomaly in the coal seam in relation to the calculated vertical stress field arising in the mined coal seam served to assess of rockburst hazard. The applied methods partially proved their adequacy in practical applications, providing valuable information on the design and performance of mining operations.

The current level of rockburst hazard in copper mines of the (LGOM) Legnica- Głogów Copper Belt Area is mostly the consequence of mining-induced seismicity, whilst the majority of rockbursting events registered to date were caused by high-energy tremors. The analysis of seismic readings in recent years reveals that the highest seismic activity among the copper mines in the LGOM is registered in the mine Rudna. This study investigates the seismic activity in the rock strata in the Rudna mine fields over the years 2006-2015. Of particular interest are the key seismicity parameters: the number of registered seismic events, the total energy emissions, the energy index. It appears that varied seismic activity in the area may be the function of several variables: effective mining thickness, the thickness of burst-prone strata and tectonic intensity. The results support and corroborate the view that principal factors influencing the actual seismic hazard level are regional geological conditions in the copper mines within the Legnica-Głogów Copper Belt Area.

This paper presents our experience obtained when mining the thick and steeply-inclined Seam 510 in the Polish Kazimierz-Juliusz coal mine with the use of a unique mechanical face mining system. Seam 510, which is 15–20 m thick and inclined at angles of 40°–45°, was initially treated as uneconomical because effective mining systems were not available. However, to extract high-quality coal resources, a completely mechanized variant of the sublevel caving system was designed based on standard machines and equipment applied in coal mining. Extraction was conducted top-down at the levels of the particular mining sub-level drifts with roof caving. The faces in the extracted coal release areas were protected by a single pair of specially designed mechanized mining system sections. One of the basic problems revealed during extraction of subsequent mining panels, was the observed changeability of the resource mining rates. The extraction losses changed in the available resources from less than 10% to about 50%. This paper presents two typical courses of changes in the extractable resource mining rates. Similar rate changes occurred in both cases with continued mining of a single seam section. Our analysis enabled deposit loss estimations and production output planning under the sublevel caving systems applied in the extraction of seam deposits of similar structure.

This article concerns numerical modeling of the impact of mining operations on fault behavior, carried out on the basis of a calculation program based on the finite element method. The calculations and their graphic results related to the reactions of vertical discontinuity on the mining operations that run along its boundary under changing operating parameters, such as geometry of the field and direction of mining with respect to the fault, as well as the method of liquidation of the caving zone. The behavior of the fault was analyzed based on distributions in the plane of shear stress and slip, together with their range and energy dissipated due to friction. The results of numerical calculations made it possible to draw conclusions on the impact of faults and the impact of operating conditions of mining in their vicinity on the level of seismic hazard.

A vast majority of hard coal deposits in Poland have a multi-seam structure, hence the presence of mining remnants left from previous operations. The impact of those remnants (exploitation edges or residual pillars) can further intensify geomechanical phenomena occurring in the rock mass, leading to changes in the original state of stress. This applies to all layers within the rock strata, including thick and coherent ones (referred to as tremor-inducing layers) where the impacts of mining remnants are likely to trigger tremors, thus enhancing the rock bursts hazard. In the light of the geomechanical model of rock strata recalled in the study, it is assumed that homogeneous and isotropic elastic layers are found between the considered mining remnant (which is revealed as the stress distribution), and the rock medium modelled as a homogeneous and isotropic half-plane. Development of the state of stress in the bedded medium was brought down to the analysis of interacting elastic layers, where the biharmonic equation is satisfied for each layer and for each respective half-plane. This equation can be solved by the integral Fourrier transform method. The impacts of the exploitation edge and the residual pillar on the elastic strain energy in the tremor-inducing layer is illustrated by recalling the Burzyński’s stress criterion. Strain energy in the tremor-inducing layer was analysed for various deformation properties of the surrounding strata and for various methods of coal extraction from the seam underneath the tremor-inducing layer. The results of the study evidence that a change in deformation properties of strata in the vicinity of the tremor-inducing layer may affect the state of stress and strain energy, which impacts on the tremor hazard levels in the vicinity of mining remnants areas.

Mining-induced seismicity in the area of development works and proper mining operations is one of the major determinants of the rockburst hazard level in underground mines. Rockburst hazard assessment in Polish collieries is performed by a variety of mining and geophysical methods, including seismic and seismoacoustic techniques, borehole surveys, small diameter drilling, rock strata profiling and analyses of geomechanical properties of rocks, geological structure and geological mining conditions. In the case of zones particularly exposed to potential hazards, it is recommended that analytical or numerical forecasts of the state of stress in the vicinity of workings should be used already at the stage of planning of mining operations. This study summarises the comparative analysis of seismic test data and analytical forecasts of the state of stress in five selected headings in one of the burst-prone collieries within the Upper Silesia Coal Basin in Poland (USCB). As regards the seismic data, duly defined quantitative indicators and energy criteria of the registered seismic activity are recalled in the assessment of rockburst hazard level during the roadheading operations. Analytical simulations utilise a developed geomechanical model and stress–strain relationships stemming from the principles of elastic media mechanics. From the standpoint of mining engineering practice, interpretation of results obtained by the two methods reveals how effective analytical models will be in prognosticating or verification of rockburst hazard conditions.