Underground Mining Research Articles

The prediction of the risks of spontaneous combustion in underground coal mines using a fault tree analysis method

Mining is one of the most risky and dangerous sectors. It is impossible to ignore the losses of life and material experienced by occupational accidents, which take place in the field of mining. Risk analysis begins with a risk assessment to identify the probability and severity of workplace hazards. Hazards must be controlled by precautions according to the risk score levels.In this study, a fault tree analysis method was conducted to analyze spontaneous combustion hazards and to predict future risks in underground coal mines. Three main causes of the top event were defined and for each of these causes, risk scores were computed using a fault tree analysis. Finally, the causes of spontaneous combustion, which is an event that is frequently encountered in coal mines, were discussed, and the spontaneous combustion risk probability was calculated as 0.3012 in cases of air entry into the gob and failure to prevent coal-air contact in development drifts. As a result of the study, the fundamental causes of spontaneous combustion, the greatest hazard in underground coal mining worldwide, have been examined in detail. The innovative approach introduced by the study aims to increase the awareness and recognition of conditions that lead to spontaneous combustion among industry workers and engineers through detailed evaluation. By doing so, it seeks to minimize the occurrence of spontaneous combustion incidents.•This paper introduces a main flowchart and countermeasure algorithm to prevent spontaneous combustion.•This paper also analyzes events which trigger spontaneous combustion and mentioned preventive measures for this events.

Implication of fault seal analysis method to evaluate the sealing conditions of major fault planes at Barapukuria basin, North-West Bangladesh

The Barapukuria coal basin stands as Bangladesh’s sole active underground coal mining site. The geological setting of this basin is marked by two major faults, the Eastern Boundary Fault and FB fault encircling the basin perimeter, alongside several smaller faults and those induced by underground longwall mining activities. A major concerning issue of this mine is the water inrush into the mine area from the extensive groundwater aquifer, Upper DupiTila (UDT). Using the Fault Seal Analysis technique employed by (Yielding et al. in Am Assoc Pet Geol Bull 81:897–917, 1997) algorithm, this analysis attempts to identify susceptible areas and potential unsealed faults that could provide the risk of water invasion into the mine area. Evaluation of Fault Seal Analysis reveals varying Shale Gauge Ratio (SGR) values: 0.08 and 0.13 for the major Eastern Boundary Fault, 0.05 for the second largest FB fault, 0.35 and 0.53 for FB-1, and 5.65, 1.69, and 1.22 for the smaller faults BGP-N-F11, BGP-N-F2, and F-24, respectively. According to SGR values, the Eastern Boundary Fault and the FB fault plane are anticipated to be unsealed and dip westward at an angle of 75°-80°, rendering them vulnerable to water inflow through the fault planes. The analysis also suggests that the Lower DupiTila (LDT) aquiclude which can impede the groundwater flow from the UDT aquifer into the mine area, is very thin or absent in the northern region of the basin making this region highly susceptible to water inundation.

The influence of cracks on pillar strength based on SRM and DFN models

This research focuses on the examination of natural fractures within underground mines, emphasizing their substantial impact on the strength and stability of ore pillars. The study adopts the Strength Reduction Method (SRM) theory and employs the Discrete Fracture Network (DFN) model, offering a novel approach to investigating the behavior of fractured rock masses. The objective of this article is to analyze the influence of natural fractures on the strength of ore pillars by employing SRM and DFN methods. The research begins by establishing a multi-level amplification program that incorporates a homogenization process. The findings reveal that, for a W/H ratio of 0.5, the strength reduction aligns consistently with empirical equations. A notable observation is that when W/H is less than or equal to 1.0, there is good agreement, but when W/H exceeds 1.0, there is a tendency to overestimate pillar strength. Subsequent investigations emphasize the significance of considering pillar development in the overall assessment of pillar forces. The study underscores the importance of integrating pillar development into the analysis, aligning with previously established research results. Therefore, by evaluating the strength and failure mechanism of columns under different aspect ratios, we studied the influence of discrete discontinuous bodies on column stability, revealed the influence of natural cracks on column strength, and provided theoretical basis and reference for the design and support of underground mines.

Application of Artificial Intelligence to the Alert of Explosions in Colombian Underground Mines

The use of Artificial Intelligence (AI), particularly of Artificial Neural Networks (ANN), in alerting possible scenarios of methane explosions in Colombian underground mines is illustrated by the analysis of an explosion that killed twelve miners. A combination of geological analysis, a detailed characterization of samples of coal dust and scene evidence, and an analysis with physical modeling tools supported the hypothesis of the existence of an initial methane explosion ignited by an unprotected tool that was followed by a coal dust explosion. The fact that one victim had a portable methane detector at the moment of the methane explosion suggested that the ubiquitous use of these systems in Colombian mines could be used to alert regulatory agencies of a possible methane explosion. This fact was illustrated with the generation of a database of possible readouts of methane concentration based on the recreation of the mine atmosphere before the explosion with Computational Fluid Dynamics (CFD). This database was used to train and test an ANN that included an input layer with two nodes, two hidden layers, each with eight nodes, and an output layer with one node. The inner layers applied a rectified linear unit activation function and the output layer a Sigmoid function. The performance of the ANN algorithm was considered acceptable as it correctly predicted the need for an explosion alert in 971.9 per thousand cases and illustrated how AI can process data that is currently discarded but that can be of importance to alert about methane explosions.

Experimental analyses of CO2 sequestration potential in mineralized fly ash and its efficacy in mitigating coal spontaneous ignition risks in underground mine goafs

To effectively utilize fly ash solid waste and realize fly ash resource utilization, carbon sequestration and emission reduction, as well as mine fire prevention and suppression, this paper analyses the components of fly ash by X-ray fluorescence spectrometer (XRF), rheological experiments, the CO2 sequestration experiments by the mineralization of fly ash, thermogravimetric analysis experiments, and flame-retardant property experiments. Additionally, the changes in the physical structure and morphology of fly ash before and after mineralization were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The carbon sequestration capacity and fluidity of fly ash slurry, as well as the ability of mineralized fly ash slurry to inhibit spontaneous coal combustion are comprehensively investigated. The research results indicate that CO2 is sequestered as calcite on the fly ash surface after mineralization. The optimal CO2 sequestration capacity of fly ash is 65.12 kg/t when 0.5 mol/L NaHCO3 is used as an additive. The fluidity of mineralized fly ash slurry is greater than that of fly ash slurry, and the lower the water-cement ratio is, the worse the fluidity. Mineralized fly ash slurry with a water-cement ratio of 3:1 has a strong carbon sequestration capacity and high fluidity, making it suitable for preventing coal spontaneous ignition in mine goafs. Mineralized fly ash slurry exhibits a regular trend where the better the mineralization effect, the lower the CO release during the low-temperature oxidation stage of coal, and the higher the cross-point temperature. Mineralized fly ash slurry has a stronger ability to inhibit spontaneous coal combustion than does ordinary fly ash slurry.

Identifying Factors Influencing Surface Deformations from Underground Mining Using SAR Data, Machine Learning, and the SHAP Method

The article presents the results of significance analyses of selected mining and geological variables for an area of underground mining activity. The study area was a region of an underground copper ore mine located in southwest Poland. The input data consisted of satellite radar data from the Sentinel 1 mission as well as mining and geological data. The line-of-sight subsidence, calculated with the use of the small baseline subset method and arranged in time series, was decomposed to extract the vertical component. The significance analysis of individual variables for the observed surface subsidence was performed using the SHapley Additive exPlanations method for the XGBoost machine learning model. The results of the analysis showed that the observed ground surface subsidence velocities were most influenced by the thickness of the PZ3 layer, which is located approximately 200 m above the roof of the mined seam, the thickness of the seam, and the timing of mining. It was also found that the proposed model was able to detect a nonlinear relationship between the analyzed excavations. The most significant influence on ground subsidence over mine excavations are mining parameters such as the spatially averaged thickness of the deposit and the time since liquidation of the deposit. The proposed approach can be successfully employed in planning both mining operations and mine closure in such a manner that the environmental impact is minimized.

Diffusion mechanism of fracture grouting in rock mass with flowing water

Grouting is a widely used geotechnical procedure known for its strong empirical properties. It has been extensively utilized for sealing subterranean water and strengthening soil and rock masses in their original locations in underground mining and underground space development. The diffusion mechanism of grouting in fractured rock is affected by the geological environment and slurry performance, which should be better revealed and characterized. In this paper, we take the surrounding rock of the roadway as the research object, consider the stress condition of the injected rock and time-dependent viscosity of the slurry, and establish fracture grouting diffusion model based on the rock composite fracture criterion. The grout strengthening mechanism is discussed based on a transparent fracture replica grouting test. According to the different transport characteristics of the slurry interacting with flowing water, it is divided into the following four areas grout-water balance area, grout loss area, stagnation area and water passage. The grout plugging mode is divided into two categories according to its final diffusion pattern: cross-section type water plugging mode and water-drop plugging mode. The pressure monitoring data of the test verified the two grout plugging modes. The diffusion distance of cis-reverse water derived in this study was in good agreement with the experimental results in grouting early stage. The research results can provide a theoretical basis for grouting engineering design.

Research on reasonable coal pillar staggered distance in shallow multi-seam mining

In shallow buried closely spaced multi-seam mining in Jurassic Coalfield in western China, due to specific reasons, it is inevitable that the lower and upper coal seam working faces and coal pillars are overlapped, resulting in stress concentration, uneven subsidence of the ground surface, the deformation and damage of the roadway intensified. In order to decrease surface damage and stress concentration, combined with physical simulation, engineering practices and theoretical analyses, reasonable coal pillar staggered distance in shallow multi-seam mining is investigated. The evolution properties of three-field (stress field, displacement field and fracture field) based on coal pillar staggered distance (CPSD) were analyzed, the determination method of rational CPSD was put up. Research findings reveal that concentrated stress results from upper and lower pillar stress superposition, and the lower pillar should be arranged in the low-stress zone. Through rational pillar arrangement, the uneven subsidence of surface is reduced, and the concentrated fractures of overlying strata and surface are decreased. For No. 1–2 and No. 2–2 coal seam mining, as CPSD is increased, subsidence above the upper coal pillar increases and the uneven subsidence of surface decreases, the concentrated stress reduced by 25%, the width of surface fractures reduced 81.1%. Consequently, rational CPSD on the basis of coupling control of three-field can be determined, the reasonable CPSD is 40–55 m. It can provide a method to realize underground safe mining and ground surface green mining in shallow multi-seam mining.

Similar experimental study on diffusion and distribution of diesel exhaust in confined space of a coal mine.

In the confined space of the underground coal mine, which is dominated by transportation lanes, explosion-proof diesel-powered trackless rubber-wheeled vehicles are becoming the main transportation equipment, and the exhaust gas produced by them is hazardous to the health of workers and pollutes the underground environment. In this experiment, a similar test platform is built to study the effects of wind speed, vehicle speed, and different wind directions on the diffusion characteristics of exhaust gas. In this paper, CO and SO2 are mainly studied. The results show that the diffusion of CO and SO2 gas is similar and the maximum SO2 concentration only accounts for 11.4% of the CO concentration. Exhaust gas is better diluted by increasing the wind speed and vehicle speed, respectively. Downwind is affected by the reverse wind flow and diffuses to the driver's position, which is easy to cause occupational diseases. When the wind is a headwind, the exhaust gases spread upwards and make a circumvention movement, gathering at the top. When the wind speed and vehicle speed are both 0.6m/s, the CO concentration corresponds to the change trend of the Lorentz function when the wind is downwind and the CO concentration corresponds to the change trend of the BiDoseResp function when the wind is headwind. The study of exhaust gas diffusion characteristics is of great significance for the subsequent purification of the air in the restricted mine space and the protection of the workers' occupational health.

An Effective Barrier Coating Technology Against Premature Bolt Failures in Underground Mines

AbstractSignificant safety and economic consequences accompany the premature failure of bolts, posing sustainability challenges for mining operations. Previous studies have indicated that hydrogen-induced stress corrosion cracking (HISCC), primarily influenced by microbial activities termed microbiologically influenced stress corrosion cracking (MISCC), stands as a major contributor to the premature failure of bolts in underground mines. Presently, an effective mechanism to mitigate these premature failures is lacking. In this study, multiple commercially available coatings undergo testing to assess their susceptibility and suitability in preventing HISCC and MISCC. Additionally, a purpose-developed coating is examined. The results reveal that the tested commercially available coatings either fail to prevent these types of corrosion or are unsuitable for the intricate conditions within underground mines. The laboratory results show the coating has a significant anti-acidic corrosion and anti-MISCC performance. Conversely, the coating formulated in this study successfully averts both MISCC and HISCC, proving its applicability within the complex geological environments prevalent in mines. This breakthrough offers a promising solution to mitigate premature bolt failures in complex underground geological environments. The developed coating presents a viable way forward for enhancing safety, reducing economic losses, and improving the overall sustainability of mining operations.

Numerical studies on the effects of the hybrid cooling and dust suppression solution in hot fully-mechanized mining face

With the increasing depth of coal mining, the hot and humid environment at the mining faces is becoming more severe. Mining in these conditions, coupled with the hazardous effects of coal dust, poses a significant risk to the health of coal miners. To improve the working conditions in underground coal mines, this study proposes a hybrid solution that combines evaporative cooling and dust suppression in fully mechanized working faces. Numerical models of the mining face are also created to simulate the cooling effects of the proposed solution. Additionally, the migration laws of water droplets from the spray system are also studied. The results indicate that the proposed solution can effectively improve thermal environments and suppress coal dust. This research can enhance the workplace safety in underground coal mines and provide valuable insights for addressing high airflow temperatures and concentrated dust levels.

Lutetian–Bartonian (Middle Eocene) micropalaeontology, biostratigraphy and palaeoecology of the Mengen Coal Basin, Northwest Türkiye (Turkey)

This study focuses on the upper Lutetian–lower Bartonian Tokmaklar Formation in the Mengen Basin of Northwest Türkiye (Turkey), examining various aspects such as biostratigraphy, palaeoecology, and isotope data (δ18O and δ13C), providing insights into the geological history and environmental conditions during this interval. Moreover, the study incorporates coal petrography on four samples to explore a potential correlation between the coalification process and the preservation of palynomorphs. The formation is informally divided into two distinct categories: a coal-bearing sequence positioned at the base of the formation and a coal-free sequence above it. However due to dense vegetation and soil cover in the area, the availability of suitable outcrops for measured sections and obtaining samples is severely limited. Therefore, we relied on drilling data from Turkish Coal Enterprises (TCE) for the purpose of coal exploration, as well as two partial sections (Ender and Çorak) from underground mining. Microapalaeontological evidences involving benthic foraminiferans, ostracods, and palynomorphs, along with isotope data (δ18O and δ13C), suggest that the Tokmaklar Formation was deposited as a result of a local transgressive process during the late Lutetian–early Bartonian. Furthermore, palynological data, particularly the existence of mangroves such as Nypa, lepidocaryoid palm and Acrostichum aureum, coupled with quantitative palaeoclimate analysis, the negative δ18O values, and the lower δ13C values indicate a warm, probably tropical climate under high rainfall.

An enhanced stability evaluation system for entry-type excavations: Utilizing a hybrid bagging-SVM model, GP and kriging techniques

In underground mining, especially in entry-type excavations, the instability of surrounding rock structures can lead to incalculable losses. As a crucial tool for stability analysis in entry-type excavations, the critical span graph must be updated to meet more stringent engineering requirements. Given this, this study introduces the support vector machine (SVM), along with multiple ensemble (bagging, adaptive boosting, and stacking) and optimization (Harris hawks optimization (HHO), cuckoo search (CS)) techniques, to overcome the limitations of the traditional methods. The analysis indicates that the hybrid model combining SVM, bagging, and CS strategies has a good prediction performance, and its test accuracy reaches 0.86. Furthermore, the partition scheme of the critical span graph is adjusted based on the CS-BSVM model and 399 cases. Compared with previous empirical or semi-empirical methods, the new model overcomes the interference of subjective factors and possesses higher interpretability. Since relying solely on one technology cannot ensure prediction credibility, this study further introduces genetic programming (GP) and kriging interpolation techniques. The explicit expressions derived through GP can offer the stability probability value, and the kriging technique can provide interpolated definitions for two new subclasses. Finally, a prediction platform is developed based on the above three approaches, which can rapidly provide engineering feedback.

Data Mining Prior to Earth Mining: A Sustainable Approach for Mineral Exploitation

The extraction of mineral resources from the earth, in various mining forms, such as open-cast and underground mining, has significant environmental and societal consequences, both during and after mining operations. It results in habitat destruction, soil erosion, deforestation, biodiversity loss, and the release of harmful pollutants into the environment. These pollutants, including heavy metals and sulphur compounds, etc., which contaminate water sources and soil, posing a serious threat to ecosystems and human health. Despite these challenges, mining remains essential for providing raw materials to meet the needs of modern civilization, and as the global population grows, demand for minerals continues to rise, leading to increased mining operations. This intensified mining activity poses a significant threat to the planet Earth. In this context, addressing the negative effects of mining, such as mining failures, and disruptions to biodiversity, is a growing concern. Mining failures encompass a range of economic, environmental, and social consequences. A comprehensive understanding of these interrelated components is crucial for mitigating the risks and consequences associated with mining failures, as well as for developing sustainable and responsible mining practices.

Ultimate Bearing Capacity of Weak Foundations under Coal Pillars

In many underground coal mines, a seam is underlain by weak floor material, and the load-carrying capacity of a pillar may be limited not by its own strength but by the bearing capacity of the floor. It has been proposed that bearing capacity may be estimated by formulae such as those of Terzaghi for structural footings on soil, but that approach is generally not valid because, for the slip surfaces assumed in the derivations of the formulae, the rock rises out of the floor beneath adjacent pillars. In the limiting equilibrium analysis proposed here, the distance to the side of a pillar to which a slip surface extends can be constrained according to the roadway or bord width. Examples are shown of the computation of bearing capacities of both homogeneous and multilayer dry and fully saturated floors, and results compared with those of elastoplastic finite element analysis. An approximate comparison with bearing capacities according to Terzaghi's formula for a strip footing is also presented for the hypothetical cases of wider roadways for which the assumed slip surfaces do not extend under adjacent pillars. For the cases considered, there is satisfactory agreement with Terzaghi’s analysis and good agreement with the results of finite element analysis. However, only one finite element analysis was carried out, and it remains to be seen whether such agreement is consistently achieved for ranges of floor strength parameters and horizontal stress.

UWB Radar Imaging Method for the Longwall Retreat and Creep Displacements Measurement in Underground Coal Mine

UWB Radar Imaging Method for the Longwall Retreat and Creep Displacements Measurement in Underground Coal Mine

A Trial Evaluation of Rock Core DCDA Absolute Shear Stress Measurement for Routine Quantitative Mining Hazard Assessment in Deep Underground High Stress Mines

A Trial Evaluation of Rock Core DCDA Absolute Shear Stress Measurement for Routine Quantitative Mining Hazard Assessment in Deep Underground High Stress Mines

Определение индивидуального риска травматизма горнорабочих в результате динамического проявления

The article analyses the effect of gas-dynamic manifestations on occupational injuries. It has been established that the most hazardous gas-dynamic manifestation for underground deep mines is a rock burst. As the rock burst is identified by the authors as the most hazardous effect by its manifestations, the authors offer their methodology of identification of occupational injury risk caused by a rock burst for a wider discussion. The main characteristics and causes of rock bursts and their signs and forecasting methods have been described. The statistics of accidents caused by rock bursts have been provided. The article contains statistical information on mild, severe, and lethal injuries caused by rock bursts in coal mines of the Kuznetsk coal basin. Multifunctional safety systems able to obtain information on the condition of rock mass have been analyzed. Special attention has been paid to the system of current control and forecast of rock mass conditions based on the «Mikon-GEO» system. In the majority of cases, based on the problems to solve, such a system is a part of multifunctional safety systems. The authors suggest that the forecast methodology is to be based on the data obtained by such systems operating based on the seismoacoustics principles. The mathematical model using the source data obtained from the «Mikon-GEO» system has been considered. The calculation algorithm enabling the assessment of the rock burst probability has been provided. The algorithm and the results of measurements of rock mass basic parameters are used to determine the individual risk value that is advisable to compare with the average value of occupational risk at production. The results obtained by the authors have been tested in one of the Kuznetsk Basin coal mines. The preliminary results of the forecast methodology use have shown the relevance of the studies and identified certain issues requiring specification and further research.

A Critical Assessment of Boundary Limits of Health Risks Associated with WBV Exposure Based on Field Studies on LHD Vehicles in Indian Underground Coal Mines

Purpose: The mining sector plays a pivotal role in meeting global resource demands, necessitating the extensive use of heavy earth-moving machinery (HEMM). Among these, load-haul-dump (LHD) mining vehicles are vital but expose operators to whole-body vibration (WBV) and shocks during their duties. Research indicates potential health risks associated with occupational WBV exposure, including musculoskeletal disorders. Evaluating these risks typically employs ISO 2631-1:1997, which, however, has limitations in addressing long-term exposure and shock effects. Methods: This study quantifies the health risks of LHD operators in Indian underground coal mines using ISO 2631-5:2018 and compares it to ISO 2631-1:1997. The methods for risk quantification from WBV vary between the two standards, leading to a comprehensive comparison. In addition, a cross-sectional study was undertaken to assess self-reported musculoskeletal pain among LHD operators. Results: The results were compared in accordance with frequency-weighted root mean square (RMS) values, vibration dose values (VDV), daily compressive dose (Sd A), and the risk of injury (RA) factor. The assessment using A(8), VDV, Sd A, and RA produced diverse evaluations, influencing varying perspectives on occupational health despite significant risks. ISO 2631-5:2018 consistently suggested a lower health risk for LHD operators as opposed to ISO 2631-1:1997. Seat effective amplitude transmissibility (SEAT) values showed amplification of vibration in the range of 4-8 Hz. Self-reported musculoskeletal pain indicated the prevalence of discomfort among operators. Conclusion: The study emphasizes a cautious approach when interpreting results and shaping guidelines to ensure sustainable development through the well-being of mining industry workers.

MECHANISED COAL EXPLOITATION IN THE "BREZJE" PIT OF THE "DJURDJEVIK" BROWN COAL MINE

In addition to the coal and electricity market and changing geopolitical circumstances, there are other sufficiently rational reasons for opening new underground mining facilities and modernizing existing mining methods.Significant limiting factors and influences, in complex mining-geological conditions, most significantly affect the possibilities of the mechanized way of mining brown coal. The "Brezje" pit is a part of the deposit where the mining-geological factors are complex and determined by the natural conditions of the deposit's genesis. Excavation methods and technologies in complex deposit conditions must be based on great flexibility and adaptability.The complexity of the tectonic structure in the "Đurđevik" pit justified the application of chamber excavation methods with borehole blasting, in various technical modifications and solutions. In all previous solutions, the degree of mechanization of the method was not significantly improved and all modifications of the chamber method were non-mechanized or semi- mechanized with a large participation of manual work, technology based on drilling and blasting, high risk of injuries, low utilization of deposits, unjustified economic effects of work. The aim of this paper is to give an adequate answer to the hypothesis "in the block structure of the deposit with pronounced tectonics, it is possible to reduce the unfavorable influence of the complex mining-geological factors of the deposit on the excavation method by choosing modern mechanization for underground exploitation". The mechanized chamber method of excavation is a conceptual solution for the possible application in complex conditions of the proposed flexible mechanization for work in the "Brezje" pit. The advantage of modern multifunctional mining machines is a high degree of adaptability to the elements of the coal layer with the use of different working mechanisms (tools) that can be changed in a very short time depending on the working phase of the process. Key words: Pit, complexity, factors, chamber method, flexible, multifunctional machine