Archives of Mining Sciences

Knowledge of the way in which minor and trace elements occur in coal is one of the most important geochemical indicators of coal quality. The differences between the methods of binding elements in coal in each coal seam and the variability of this feature of coal in the basin profile have not been discussed so far. These coal features were identified in a group of selected coal seams (209, 401, 405, 407, 501, 504, 510, 615, 620) in the Upper Silesian Coal Basin (USCB). At the same time, the differences in the role of identified mineral and maceral groups in concentrating specific elements in coal is highlighted. Identical or similar tendencies of changes in the way in which As and V, Ba and Rb, Co and Pb, Co and Zn, Mn and Pb, Pb and Zn, Co and Rb, and for Cr and Cu occur in the coal seams in the USCB profile was found. Changes in the mode of occurrence of As and Pb in coal in the USCB profile were probably influenced by carbonate mineralization. The changes in the mode of occurrence of Mni and Pb in the coal were probably determined by dia and epigenetic sulfide mineralization, while the content of Ba, Cr, Rb, Sr, and V in coal from these deposits was affected by clay minerals. It was observed that the greater the degree of the carbonization of the organic matter of coal, the lower the content of As, Mn and Pb in coal and the higher the content of Ba and Sr in coal.

The application of fluidized fly ash in underground mining excavations is limited due to its significant content of free calcium and calcium sulfate. In order to increase the amount of utilized fly ash from fluidized beds, it should be converted to a product with properties that meet the requirements for mining applications. This research presents the results of an attempt to adapt fluidized fly ashes for use in underground mining techniques, by means of carbonation and granulation. Carbonation was performed with the use of technical carbon dioxide and resulted in the reduction of free calcium content to a value below 1%. Granulation on the other hand, resulted in obtaining a product with good physical and mechanical parameters. The performed mineralogical and chemical studies indicate that trace amounts of “binding” phases, such as basanite and/or gypsum are present in the carbonized ash. The addition of water, during the granulation of carbonized fluidized fly ash, resulted in changes in the mineral phases leading to the formation of ettringite and gypsum as well as the recrystallization of the amorphous substance. It was confirmed that the carbonization and granulation of flying fluidized ashes positively affects the possibility of using these ashes in underground mining excavations.

In this article, the issue of mining impact on road pavements and subgrade is presented, taking into account the interaction between geosynthetic reinforcement and unbound aggregate layers. Underground mining extraction causes continuous and discontinuous deformations of the pavement subgrade. Structural deformations in the form of ruts are associated with the compaction of granular layers under cyclic loading induced by heavy vehicles. Horizontal tensile strains cause the loosening of the subgrade and base layers. The granular layers under cyclic loading are additionally compacted and the depth of ruts increases. Moreover, tensile strains can cause discontinuous deformations that affect the pavement in the form of cracks and crevices. Discontinuous deformations also affect the pavement in the fault zones during the impact of mining extraction. The use of geosynthetic reinforcement enables the mitigation of the adverse effects of horizontal tensile strains. Horizontal compressive strains can cause surface wrinkling and bumps. Subsidence causes significant changes in the longitudinal and transverse inclination of road surface. Both examples of the laboratory test results of the impact of subgrade horizontal strains on reinforced aggregate layers and the selected example of the impact of mining deformation on road subgrade are presented in this article. The examples show the beneficial impact of the use of geosynthetic reinforcement to stabilize unbound aggregate layers in mining areas.

A simple empirical study on the orientation, diameter, and extent of radial fractures (long and short) at the vicinity of the face-perpendicular preconditioned boreholes is described. Homogenous and heterogeneous mining faces were considered when studying the orientation of radial fractures, four and five face-perpendicular preconditioning practices were used to investigate the outspread and diameter of radial fractures from one blasted drill hole to another. Long radial fractures were observed to be developed along the direction of the maximum principal stress and short radial fractures were observed to be developed along the direction of the intermediate principal stress in a homogenous mining face. On the other hand, long radial fractures were observed to be developed along the direction of the intermediate principal stress, while short radial fractures were observed to be developed along the direction of the maximum principal stress when the mining faces subjected to heterogeneous rock mass. The diameters of the radial fractures observed were inconsistent and were not nine times the diameter of the original borehole. Furthermore, the extent of radial fractures from one borehole to another was noted to be gradually improved when the additional of preconditioned borehole was in place. This study maintained that the orientation of radial fractures is mostly controlled by the rock properties, however, extend and the diameters of the radial fractures are controlled by rock properties, the effectiveness of the stress wave and gas pressure and brittleness of the rock mass.

The prediction of rock cuttability to produce the lignite deposits in underground mining is important in excavation. Moreover, the certain geographic locations of rock masses for cuttability tests are also significant to apply and compare the rock cuttability parameters. In this study, sediment samples of two boreholes (Hole-1 and Hole-2) from the Sagdere Formation (Denizli Molasse Basin) were applied to find out the cerchar abrasivity index (CAI), rock quality designations (RQD), uniaxial compressive strengths, Brazilian tensile strengths and Shore hardnesses. The Sagdere Formation deposited in the terrestrial to shallow marine conditions consists mainly of conglomerates, sandstones, shales, lignites as well as reefal limestones coarse to fine grained. A dataset from the fine grained sediments (a part of the Sagdere Formation) have been created using rock parameters mentioned in the study. Dataset obtained were utilized to construct the best fitted statistical model for predicting CAI on the basis of multiple regression technique. Additionally, the relationships among the rock parameters were evaluated by fuzzy logic inference system whether the rock parameters used in the study can be correlated or not. When comparing the two statistical techniques, multiple regression method is more accurate and reliable than fuzzy logic inference method for the dataset in this study. Furthermore, CAI can be predicted by using UCS, BTS, SH and RQD values based on this study.

In recent decades, two different approaches to mine ventilation control have been developed: ventilation on demand (VOD) and automatic ventilation control (AVC) systems. The latter was primarily developed in Russia and the CIS countries. This paper presents a comparative analysis of these two approaches; it was concluded that the approaches have much in common. The only significant difference between them is the optimal control algorithm used in automatic ventilation control systems. The paper describes in greater detail the algorithm for optimal control of ventilation devices that was developed at the scientific school of the Perm Mining Institute with the direct participation of the authors. One feature of the algorithm is that the search for optimal airflow distribution in the mine is performed by the system in a fully automated mode. The algorithm does not require information about the actual topology of the mine and target airflows for the fans. It can be easily programmed into microcontrollers of main fans and ventilation doors. Based on this algorithm, an automated ventilation control system was developed, which minimizes energy consumption through three strategies: automated search for optimal air distribution, dynamic air distribution control depending on the type of shift, and controlled air recirculation systems. Two examples of the implementation of an automated ventilation control system in potash mines in Belarus are presented. A significant reduction in the energy consumption for main fans’ operation obtained for both potash mines.

The correct management of underground works, petroleum and gas reservoirs and geothermal applications relies on the hydromechanical behaviour of rock masses. We describe a laboratory approach to measuring permeability for different types of rock specimens. A laboratory system was designed and set up using rock mechanics equipment (a servo-controlled hydraulic press, a Hoek cell, a pump for injecting water and a scale for measuring the volume of water flow). To verify the validity of the permeability measurements, tests were carried out on a reference porous rock (Corvio sandstone), with results showing good agreement with those published in the literature. Tests were subsequently carried out on artificially fissured granite specimens with different joint patterns, submitted to various confinement stresses up to 20 MPa. Results showed good agreement with traditional Klinkenberg test results. Other tests done with artificially fissured specimens are described for demonstrative purposes.

Blasting cost prediction and optimization is of great importance and significance to achieve optimal fragmentation through controlling the adverse consequences of the blasting process. By gathering explosive data from six limestone mines in Iran, the present study aimed to develop a model to predict blasting cost, by gene expression programming method. The model presented a higher correlation coefficient (0.933) and a lower root mean square error (1088) comparing to the linear and nonlinear multivariate regression models. Based on the sensitivity analysis, spacing and ANFO value had the most and least impact on blasting cost, respectively. In addition to achieving blasting cost equation, the constraints such as fragmentation, fly rock, and back break were considered and analyzed by the gene expression programming method for blasting cost optimization. The results showed that the ANFO value was 9634 kg, hole diameter 76 mm, hole number 398, hole length 8.8 m, burden 2.8 m, spacing 3.4 m, hardness 3 Mhos, and uniaxial compressive strength 530 kg/cm2 as the blast design parameters, and blasting cost was obtained as 6072 Rials/ton, by taking into account all the constraints. Compared to the lowest blasting cost among the 146-research data (7157 Rials/ton), this cost led to a 15.2% reduction in the blasting cost and optimal control of the adverse consequences of the blasting process.

In this work, the support of two general galleries located in poor quality rock mass and subjected to the influence of high thickness coal layer exploitations is designed and optimized. The process is carried out in four phases:

A first preliminary support is defined employing different geomechanical classifications and applying the New Austrian Tunnelling Method (NATM) using bolts and shotcrete.

An instrumentation campaign is carried out with the goal of analysing the behaviour of the support. The study noticed the failure of the support due to the time of placement of the different elements.

A back-analysis using the Flac and Phases software has allowed the evaluation of the properties of the rock mass and the support, the study of the influence of the time of placement on the component elements (bolts and shotcrete), and the redefinition of that support.

Subsequently, a new support is designed and optimized through numerical modeling after the start of mining without experience in these sizes of sublevel caving that caused the failure of the previously designed support. The new support is formed by yieldable steel arches that are more suitable to withstand the stresses generated by nearby mining work.

In the Canary Islands, groundwater is the main source of drinking water. Groundwater mines have been the system used by the engineers of the archipelago to collect water from the ground. The Canary Islands are volcanic with soils characterized by being rich in uranium, the disintegration of which gives rise to radon gas. In this study, radon gas levels in the mines on two islands of the archipelago have been measured to study exposure to this gas in the galleries. Results show values much higher than the European regulatory limit concentrations.

The paper presents a brief outline of the European Union Climate and Energy Package in early 2020, as well as the EU’s plans in this respect until 2030 (Winter Package and Green Deal) and even further until 2050 (EU’s climate neutral target). Also the current condition of power generation in Poland and challenges for Polish energy sector in the nearest future are discussed. The Energy Policy of Poland until 2040 (EPP 2040) is analysed in relation to possible risks and dangers. Some improvements are proposed in regard to the implementation of the document. In addition, the current volume and perspectives of hard coal and lignite mining in Poland until 2040 are discussed and compared with an expected demand for coal in Polish power plants and combined heat and power stations. On the basis of the prognosis of energy consumption in the period 2031-2040, there seems to appear a serious risk of energy shortage due to a possible delay in a nuclear power project and lack of lignite mining at the level defined in EPP 2040 policy. Therefore, some variants of providing the security of energy supplies are taken into account and thoroughly analysed in the paper.

Coal waste stockpiles – as artificial formations being a result of the exploitation of underground coal deposits – are constantly influenced by external factors, such as rock mass movements affecting the stability of the stockpile body and changing weather conditions, leading to a cycle of aerological phenomena which intensify the self-heating of the deposited material. Together with the occurrence of external factors, the stored material is also characterised by a set of internal features (also called genetic) that have a direct impact on the kinetics of the self-heating reaction.

The paper focuses mainly on the issue of external factors such as the inclination angle of the stockpile, erosion of the slopes and thermal insulation of the layers of the stored material, which affect the phenomenon of self-heating of the material. Studies of impact of these factors on the thermal stability of coal waste stockpiles are important in the aspect of secondary exploitation of the stockpiles as well as during their reclamation or revitalisation. The numerical solutions presented in the paper should be treated as guidelines that define the directions of analysis for specific cases.