Coal Mine Research Articles

Multisolid waste collaborative production of aeolian sand-red mud-fly ash cemented paste backfill

This study proposed the novel idea of anaolian sand-red mud-fly ash cemented paste backfill (ARFCPB) to realize low-carbon backfill mining. This idea realizes large-scale disposal and resource utilization of red mud (RM) and fly ash (FA) solid wastes. The influence of the FA/RM mass ratio and mass concentration on the mechanism of action of ARFCPB was explored through comprehensive rheological performance, mechanical property, microscopic, and leaching toxicity tests. The results showed that the fresh ARFCPB slurry could be described by the Herschel–Bulkley model (R2 ≥ 0.964). As the FA/RM mass ratio increased, the ARFCPB slurry yield stress decreased, the thixotropy decreased, and the slump increased. This is because RM has a large specific surface area and an unsmooth surface, resulting in greater water absorption by RM than by FA. In addition, the uniaxial compressive strength (UCS) of ARFCPB can meet the needs of backfill mining with higher strength requirements. UCS first increases and then decreases with increasing FA/RM mass ratio, which is optimal when the mass ratio of FA to RM is 4. When the FA/RM mass ratio was 4, the UCSs of specimens A4 and B4 with mass concentrations of 78% and 80%, respectively, were 5.6MPa and 6.4MPa after 28 days of curing. The leaching results of heavy metal ions in group B4 meet the Class III groundwater standards and can be used for centralized drinking water sources and industrial and agricultural water. Considering the fluidity characteristics, mechanical properties, and leaching results, B4 was identified as the optimal formulation. Finally, the microstructure of the ARFCPB was studied using ultrasonic pulse velocity (UPV) and SEM. The results can contribute to clean production in the aluminum production industry, coal-fired power plants, and coal mines.

Manufacturing Artificial Aggregates from Overburden Coal Mine Waste and Their Properties for Pavement Applications

Manufacturing Artificial Aggregates from Overburden Coal Mine Waste and Their Properties for Pavement Applications

Processing Coal Mine Acidic Water Using Nanofiltration Membrane in West Aceh

Processing Coal Mine Acidic Water Using Nanofiltration Membrane in West Aceh

Estimating resource rents for Mozambique

This paper estimates resource rents for Mozambican coal mining using company-level data employing the residual value method devised by SEEA-Energy (the multi-purpose conceptual framework for organising energy-related statistics) and compares the findings with the World Bank's estimates of coal rents. The latter estimates are often used in the resource curse literature and also guide the World Bank's policy notes, forming the baseline of their policy advice on resource exploitation. On average, the results show unit coal rents for the 2011–2020 period that are less than half of the World Bank estimates, suggesting that the World Bank overstates coal rents for Mozambique considerably. The main driver of this discrepancy is the World Bank's underestimation of extraction costs. The results suggest that studies employing resource rent estimates should consider sensitivity analyses and greater use of local data, and that the World Bank's policy advice should be interpreted cautiously to avoid unreasonably high expectations.

The Sovereign Debt Crisis in Sri Lanka: Anatomy and Policy Options

Abstract During the COVID-19 pandemic, there was a dramatic increase in national debt levels across the world, with reported cases of downgrading sovereign debt ratings and difficulty of fulfilling debt obligations (“debt distress”), heavily concentrated in low- and middle-income countries. In this context, the unfolding sovereign debt crisis in Sri Lanka has attracted worldwide attention as the canary in the coal mine for what could become a global “development” crisis. This paper examines the Sri Lankan crisis encompassing both the sources of vulnerability to the COVD-19 shock, and stabilization and structural adjustment reforms after the debt default, with emphasis on the systemic “solvency” challenge of dealing with the massive debt overhang evolved over the previous two decades. The prime focus of the Extended Fund Facility (EFF) program that Sri Lanka signed with the IMF in March 2023 is on economic stabilization through fiscal consolidation. This paper makes a strong case for combining economic stabilization with coherent structural adjustment policies to redress the long-standing antitradable bias in the incentive structure that underpinned vulnerability of the economy to external shocks.

Study on the Influence of Some Ventilation Parameters on Dust Dispersion in Heading Face Coal Mine Using CFD Numerical Model

Coal dust is one of the environmental factors that seriously affect the health of workers as well as the mining equipment in underground coal mines. At present, coal dust is commonly generated during drilling, blasting, excavation, and transportation processes in mining operations. During mining blasting processes, coal dust is generated with varying particle sizes and high concentration levels. High concentrations of dust will affect mining operations and increase the ventilation time required for mining faces. In addition, coal dust exists in suspended form in the roadway and is harmful to human health, especially fine dust particles that have a negative impact on work efficiency. To improve ventilation efficiency and eliminate coal dust, this article presents a CFD-DPM numerical modeling method that integrates a DEM collision model based on the finite element method to analyze the motion characteristics of airflow and dust particles in the mine tunnel, while considering collisions between particles and between particles and walls. The article analyzes the distribution of wind speed, the dispersion of dust in the space around the roadway, and dust concentrations at distances of 1 m, 3 m, and 6 m from the working personnel and at a position 1.5 m above the roadway floor, corresponding to the breathing zone of the workers, with varying parameters such as velocity and duct position. The results indicate that with a wind velocity of V = 18 m/s and an air duct height h = 3.0 m, the best dust reduction results are achieved, and they provide theoretical guidance for selecting and optimizing ventilation parameters in dust control.

Study on the Influence of Grouting Treatment on the Movement and Deformation of Surface in Longwall Coal Mining Goaf Areas

Study on the Influence of Grouting Treatment on the Movement and Deformation of Surface in Longwall Coal Mining Goaf Areas

Thin seams and small mines are associated with higher exposures to respirable crystalline silica in US underground coal mines

ObjectivesPrevious radiologic and histopathologic studies suggest respirable crystalline silica (RCS) overexposure has been driving the resurgence of pneumoconiosis among contemporary US coal miners, with a higher prevalence of severe disease...

Life Cycle Mining Deformation Monitoring and Analysis Using Sentinel-1 and Radarsat-2 InSAR Time Series

The life cycle of mining results in various patterns of surface deformation as it progresses through development, production, and reclamation. Therefore, the spatial–temporal patterns of ground deformation provide a crucial indicator to understand the mining activities, related geohazards, and environmental restoration. This study investigates the decadal deformation (2012–2022) of three coal mines during different stages of mines’ life cycles in Henan, China, using radar interferometry with Radarsat-2 and Sentinel-1 data. The results reveal multiple deformation patterns across different areas: the Changcun mine area changed from ground subsidence to uplift following the termination of exploitation in 2016; the Xiadian mine area has been continuously developing over the past decade, resulting in a cumulative subsidence of 55.6 mm; and the Liyuan mine area exhibits surface rebound at a rate of 7.9 mm/year since its closure in 2007. We also probe the mining geometry of the production process by using a rectangular model. This study highlights the significance of long-term InSAR observations and deformation modeling in elucidating the mining operation dynamics of small mining zones in their production, transition, and post-closure periods, thereby facilitating the management of small-scale mining.

System simulation and parametric analysis of low-concentration coal mine gas fed SOFC-CHP with deoxygenation and enrichment pretreatment

Solid oxide fuel cell (SOFC) combined heat and power (CHP) can efficiently convert low-concentration coal mine gas (LC-CMG) into clean energy, avoiding the greenhouse effect of LC-CMG. Deoxygenation and methane enrichment pretreatment of LC-CMG can prevent explosion and anode oxidation risk. Herein, a chemical process model of LC-CMG fed SOFC-CHP system with the pretreatment was established to predict the performances under different operating conditions. Performance evaluation and exergy analysis were performed considering the use of oxygen-rich gas from the pretreatment at SOFC cathode. The effects of key operation parameters on system performances were investigated in terms of residual oxygen concentration, inlet methane concentration, fuel flow and fuel utilization. The results indicated that net electrical efficiency and heat supply efficiency can respectively reach 49.13 % and 23.90 % using LC-CMG of 15 % CH4 with enhancing effect of oxygen-rich gas at cathode. The decrease of methane concentration and the increase of residual oxygen concentration and flow rate caused the decreased electrical efficiency but the increased heat supply efficiency due to the enlargement of concentration polarization and heat supply. The optimal operation parameters were recognized by comprehensively considering diverse performance indicators. This work can guide system integration and operation optimization of LC-CMG fed SOFC-CHP.

Hydration mechanism of limestone calcined clay cement containing calcined coal gangue

Coal gangue (CG), a byproduct of coal washing and mining, has experienced a substantial increase in production in tandem with rising energy consumption trends. The utilization of calcined CG as an additive to cementitious materials is considered a potentially effective strategy for CG management and expanding its applicability on a large scale. This research investigates the impact of calcined CG on the characteristics of blended cements by applying isothermal calorimetry, X-ray diffraction (XRD), Mercury Intrusion Porosimetry (MIP), and mechanical assessments. This paper investigates four separate binder systems: Ordinary Portland Cement (OPC), OPC incorporating 30 % calcined CG, OPC with 15 % limestone addition, and limestone calcined clay cement (LC3). The XRD analysis of the hydrate phase assemblage indicated that the hydrates in LC3 systems exhibit a notable increase, consequently leading to a significant reduction in porosity by MIP results. Furthermore, LC3 systems show greater refinement in pore structure compared to other blended cements. These findings present novel opportunities for furthering the utilization of coal gangue and extending the applications of LC3 cement.

An entropy based spatial-temporal cube with its application to assess stress of overburden due to mining.

Underground coal seam mining significantly alters the stress and energy distribution within the overlying rock, leading to eventual structural degradation. Therefore, it is imperative to quantitatively identify the temporal and spatial characteristics of stress evolution of overlying rock caused by mining. This paper introduces a novel rock stress model integrating entropy and a spatial-temporal cube. Similar material model tests are used to identify the abrupt entropy changes within the mining rock, and the trend analysis is carried out to describe the spatial-temporal evolution law of stress during mining. Experimental findings indicate elevated stress levels in the unmined rock preceding and following the panel, as well as within specific rock strata above it. Definitively, dynamic stress arches within the surrounding rock of the stope predominantly bear and distribute the load and pressure from the overlying rock, and each stress mutation is accompanied by a sudden stress entropy change. Over time, z-score shows that the noticeable reduction in mining-induced overburden stress becomes increasingly pronounced, especially in the water-conducting fracture zone. The model's bifurcation set serves as the comprehensive criterion for the entropy-induced sudden changes in the rock system, signifying overall failure.

In Situ Lung Dust Analysis by Automated Field Emission Scanning Electron Microscopy With Energy Dispersive X-ray Spectroscopy: A Method for Assessing Inorganic Particles in Lung Tissue From Coal Miners.

Overexposure to respirable coal mine dust can cause severe lung disease including progressive massive fibrosis (PMF). Field emission scanning electron microscopy with energy dispersive x-ray spectroscopy (FESEM-EDS) has been used for in situ lung dust particle analysis for evaluation of disease etiology. Automating such work can reduce time, costs, and user bias. To develop and test an automated FESEM-EDS method for in situ analysis of inorganic particles in coal miner lung tissue. We programmed an automated FESEM-EDS procedure to collect particle size and elemental data, using lung tissue from 10 underground coal miners with PMF and 4 control cases. A statistical clustering approach was used to establish classification criteria based on particle chemistry. Data were correlated to PMF/non-PMF areas of the tissue, using corresponding brightfield microscopy images. Results for each miner case were compared with a separate corresponding analysis of particles recovered following tissue digestion. In situ analysis of miner tissues showed higher particle number densities than controls and densities were generally higher in PMF than non-PMF areas. Particle counts were typically dominated by aluminum silicates with varying percentages of silica. Compared to digestion results for the miner tissues, in situ results indicated lower density of particles (number per tissue volume), larger size, and a lower ratio of silica to total silicates-probably due to frequent particle clustering in situ. Automated FESEM-EDS analysis of lung dust is feasible in situ and could be applied to a larger set of mineral dust-exposed lung tissues to investigate specific histologic features of PMF and other dust-related occupational diseases.

Research on the Explosion Reaction Mechanism of Volatile Gases from Coal Dust Pyrolysis

ABSTRACT It is imperative to have an in-depth understanding of the coal dust explosion reaction mechanism to control and prevent coal explosions in the coal mining industry and promote the safe and efficient utilization of coal resources. The volatile gases are the primary components involved in coal dust explosion reactions. Therefore, studying the explosion reaction mechanism of volatile gases in coal dust is of great significance for revealing the process of coal dust explosion. This study conducted a thermogravimetric mass spectrometry (TG-MS) experiment to analyze the mass loss characteristics and volatile gas components during coal dust pyrolysis. Experimental results showed that the pyrolysis process of coal dust is mainly divided into three stages. The main components of volatile gases escaping from coal dust pyrolysis are CO, CH4, CO2, and H2O. Then, the Chemkin-Pro numerical simulation method was also introduced to analyze the mixture explosion reaction process of coal dust pyrolysis volatile gas. The sensitivity analysis and the rates of production analysis (ROP) of reactants, products, and intermediate products during the volatile gas explosion reaction were conducted. Furthermore, 14 components and 27 key elementary reactions involved in the reaction process were simplified and extracted. A simplified reaction pathway for the mixture explosion of coal dust pyrolysis volatile gas was constructed. This study introduces a novel approach to investigate the mechanism of homogeneous combustion of volatile gases in coal dust explosion reactions.

A Method for Evaluating the Data Integrity of Microseismic Monitoring Systems in Mines Based on a Gradient Boosting Algorithm

Microseismic data are widely employed for assessing rockburst risks; however, significant disparities exist in the monitoring capabilities of seismic networks across different mines, and none can capture a complete dataset of microseismic events. Such differences introduce unfairness when applying the same methodologies to evaluate rockburst risks in various mines. This paper proposes a method for assessing the monitoring capability of seismic networks applicable to heterogeneous media in mines. It achieves this by integrating three gradient boosting algorithms: Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LightGBM), and Categorical Boosting (CatBoost). Initially, the isolation forest algorithm is utilized for preliminary data cleansing, and feature engineering is constructed based on the relative locations of event occurrences to monitoring stations and the working face. Subsequently, the optimal hyperparameters for three models are searched for using 8508 microseismic events from the a Coal Mine in eastern China as samples, and 18 sub-models are trained. Model weights are then determined based on the performance metrics of different algorithms, and an ensemble model is created to predict the monitoring capability of the network. The model demonstrated excellent performance on the training and test sets, achieving log loss, accuracy, and recall scores of 7.13, 0.81, and 0.76 and 6.99, 0.80, and 0.77, respectively. Finally, the method proposed in this study was compared with traditional approaches. The results indicated that, under the same conditions, the proposed method calculated the monitoring capability of the key areas to be 11% lower than that of the traditional methods. The reasons for the differences between these methods were identified and partially explained.

Experimental research on creep characteristics and failure mechanism of mining roadway in nearly vertical coal seams

Introduction: Nearly vertical coal seams present a significant challenge for the coal mining industry due to their difficult accessibility. However, these seams account for a substantial proportion of the world’s coal reserves. Therefore, it is vital to conduct research on disaster control techniques for safe mining of these seams.Method: The research team used experimental research, theoretical analysis, and numerical calculation methods to investigate the creep characteristics and failure mechanisms of layered sandstone roadway in nearly vertical coal seam.Results and discussion: These findings revealed that the maximum moment and concentrated stress of the sandstone located on the side of the roadway roof was positioned in the middle of the nearly vertical structure, making it more susceptible to transverse shear failure. On the other hand, the nearly vertical structure on the floor side was prone to shear slip failure initiated from the bottom of the structure. This led to the asymmetric instability of the roadway. The practical implications of this research are significant for the safe mining of nearly vertical coal seams. The results could help inform the development of disaster control techniques.

Effects of deep coal mining on groundwater hydrodynamic and hydrochemical processes in a multi-aquifer system: Insights from a long-term study of mining areas in ecologically fragile western China

The groundwater hydrodynamic and hydrochemical process of the multi-aquifer system will experience complicated and serious influence under deep coal mining disturbance. There is relatively little research that has integrated hydrodynamic and hydrochemical properties of groundwater to investigate the spatiotemporal distribution characteristics and evolution patterns of hydrogeochemistry and hydrodynamic information in deep multi-aquifer systems. The study of the groundwater hydrodynamic and hydrochemical spatiotemporal coupling response of multi-aquifer systems under the deep and special thick coal seam mining-motivated effect in ecologically fragile western mining areas is of great significance for the safe mining of coal resources and ecological environment protection. In this research, the hydrochemical analysis data composed of 218 groundwater samples from Tangjiahui coalfield, Northwest China with 1526 measurements and a 6-year (2016–2021) sampling period were collected for studying the hydrogeochemical spatiotemporal evolution process and governing mechanism of the multi-aquifer system using hierarchical cluster analysis, ion-ratio method, saturation index and multidimensional statistical analysis. Additionally, wavelet analysis and cross-wavelet coherence analysis were implemented to quantitatively recognize the spatiotemporal variation characteristics of hydrodynamic information and analyze the coherence relationships between time series. The results demonstrate that the hydrochemical characteristics exhibit significant spatial differences, while the temporal variation of hydrochemical characteristics in the Permian Shanxi Formation fractured sandstone aquifer (PSFFA), mine water (MW), and Ordovician karst limestone aquifer (OKA) is not significant. The water-rock interaction is the predominant control mechanism for the spatial evolution of hydrogeochemistry in the research area. Moreover, the large-scale mining of deep coal seams controls the type and degree of water-rock interactions by damaging the structure of aquifers and altering the hydrodynamic conditions of groundwater. The period from 2016 to 2021 exhibits multi-time scale characteristics in time series of precipitation, mine water discharge, and the water level of PSFFA and OKA. The mine water discharge has a positive correlation with the water level of PSFFA and OKA, whereas the significant period of precipitation and the water level of PSFFA coherence is not obvious. The research findings not only provide in-depth insights to protect the groundwater resources in water-shortage mining areas but also promote the secure mining of deep coal resources.

Stability evaluation of open-pit mine slope based on Bayesian optimization 1D-CNN

As mechanized open-pit coal mining intensifies, assessing and predicting slope stability has become increasingly important. To address the limitations of traditional mechanical calculations, numerical simulations, and physical experiments, this paper identifies the key factors impacting slope stability in open-pit mines and develops a multi-parameter sample data set. The study employs hyperparameters optimized using a Bayesian algorithm, introduces additional convolutional layers, and combines the Adam optimizer with dropout techniques to enhance the feature extraction and performance of one-dimensional convolutional neural networks (1D-CNN). This leads to a Bayesian-optimized one-dimensional convolutional neural network (B-1D MCNN) model for predicting slope stability.The study evaluates the classification performance and accuracy of various models for slope stability, including BP neural networks, genetic algorithm-optimized convolutional neural networks, 1D-CNN, and B-1D MCNN, using accuracy, precision, and F1-score as metrics. The analysis also examines the influence of factor indicators and training set length on the model's output to assess its generalization capabilities.The research findings suggest that: (1) the B-1D MCNN model for evaluating slope stability demonstrates the capability to accurately depict the nonlinear correlation between influencing factors and slope stability. (2) Compared with other models, the B-1D MCNN model has shown enhancements of 10.96% to 27.85%, 10.26% to 28.55%, and 8.98% to 25.05% in terms of Accuracy, F1-Score, and Precision, respectively. (3) As the length of the training dataset increases, the performance of the model improves accordingly. (4) The B-1D MCNN model shows a generalization power of 87.5%.

Profit Over People: Killing a Tribal Movement Against Corporate Mining in India

Coal mining and coal use have been the most significant cause of global warming. It damages the environment and affects the lives, livelihood and culture of the indigenous people who live in a coal mining area. Resistance and rejection have been strong among those people. The article examines a people’s movement in Jharkhand, India, that resisted an open-pit corporate coal mine. The case study explains how they organized and mobilized into a strong movement. It also describes what happens to the poor indigenous when a company disrespects an agreement. The article raises some fundamental ethical questions for the future of people’s movements, mining companies, national governments, and the survival of our earth.

The Donetsk Region's coal industry: Activation of innovation processes

Subject. This article discusses the issues of managing the coal sector of the economy. Objectives. The article aims to form a mechanism for the implementation of innovation processes in the coal mining industry, taking into account the economic interests of the Donetsk People's Republic. Methods. For the study, we used systems and comparative analyses. Results. The article proposes an organizational and economic mechanism that provides an optimal combination of traditional goals and long-term objectives to intensify innovation processes in the coal industry, the main directions of development of which are the creation of clusters and technical re-equipment of enterprises. Conclusions. In the Donetsk region, measures have been taken to attract investment and create favorable conditions for business.