Coal Mining District Research Articles

‘Black Gold’ and Verticality: Geology, Labour and Mining Operations in the Territorial Construction of the Witbank Labour District

Scholars acknowledge the importance of geological knowledge in the growth of South Africa’s mining industry. While this acknowledgement extends to the analysis of the rise of eMalahleni (formerly known as Witbank) to the status of ‘premier coal supplier’ of the Union of South Africa, there is currently no specific historical analysis of the role of geological knowledge in the growth and development of the district’s mining industry. This article is a response to Kate (formerly Peter) Alexander’s call to study the history of mining with reference to the contribution of geological knowledge, and provides a detailed historical account of such a contribution to the development of the political economy of the mining industry of eMalahleni. 1 Using a wide range of archival sources, the article draws from literature on the production of vertical territory and takes as its starting point the role of scientific societies such as the Geological Society of South Africa and the South African Institute of Mining and Metallurgy in the creation of geological knowledge about the coal deposits of the former Transvaal. It then examines the roles of the Transvaal Geological Survey and the Geological Survey of the Union of South Africa, as well as geological maps produced by Alexander Graham in the creation of the Witbank Coalfield, to demonstrate how the development of geological knowledge and mining operations became processes that defined the constitution of the Witbank Labour District. The paper argues that the making of the Witbank Labour District as a coal-mining district was tied to the making of the Witbank Coalfield and that the making of the coalfield from which the district’s mining industry developed was a process in which the availability of labour was as crucial a factor in the expansion of its mining operations as scientific societies, shafts, drilling operations and expert geological knowledge.

Anomalous position of Paleozoic faults of Western Donbas

Statement of the general problem. The oil and gas-bearing province of Eastern Ukraine is located in the Dnipro-Donetsk Basin (DDB). It covers the Paleozoic structural floor and is buried under younger sediments. The Paleozoic structural floor of the territory is represented as a long rift graben. The maximum thickness of the sedimentary cover in the graben is 15–17 km. According to geophysical data, the thickness of the earth's crust is 31–32 km under the axial part of the DDB and increases towards the sides. But according to the maximum thickness and facies characteristics of the Paleozoic deposits, the thickness of the Earth's crust below them could not exceed 20 km. The modern thickness is 1.5 times higher. Therefore, such a geological-geophysical model of the structure of the DDB is contradictory. Analysis of recent research and publications. The removal of the contradiction is possible due to the detection of a series of Hercynian thrusts with total amplitude of thrusts of the order of 50 km. Such thrusts began to be established on the northern and southern flanks of the DDB. Hercynian thrusts have a southwestern vergence. In the north, the Voronezh crystalline massif is pushed onto the DDB along the Noviy thrust with an amplitude of 9–10 km. In the south, the South Donbas melange zone is established, which pushes the folded Donbas onto the Ukrainian shield. On its continuation to the northwest is the southern side of the DDB - the so-called Southern monocline. The well-studied Pavlograd-Petropavlovsk coal mining district of Western Donbass with operating coal mines is located within its borders. An unsolved part of the overall problem. Numerous faults with relatively small amplitudes are established within the Paleozoic Southern Monocline. Together, they form a system of horsts and grabens with a north-western extension. But the bottom parts of the grabens are 1–3 km higher than the tops of the horsts. Such a geological situation is anomalous. This indicates the post-fault dislocation of the horst-graben system as a whole. The purpose of the article is identification of the causes of the anomalous structural position of the graben-horst system in the modern geological structure of the Southern Monocline and in the general model of the geological structure of Eastern Ukraine. Research materials and methods. Were involved more than 390 geological sections, constructed based on the data of more than 10,000 wells. Of them, 265 wells revealed the folds that are being analyzed. In addition, were used data of catagenetic transformations of the sedimentary section. Presentation of the main research material. The South Donbas mélange zone falls to the northeast and continues under the Southern Monocline. It is located in the upper block of this regional thrust structure and is in an allochthonous setting. According to geological data, the true amplitude of the thrust of Western Donbas on the Ukrainian shield is 15–20 km, and the vertical component of this amplitude exceeds 3 km. Such spatial parameters explain the abnormality of the structural position of the horsts and grabens of Western Donbass - their southwestern flanks were significantly raised relative to the northeastern flanks during thrusting. Scientific novelty. Therefore, in the modern geological structure, the Dnipro-Donetsk "basin" is not a rift, but a post-rift Hercynian folded region. It is formed by high-amplitude thrusts on the northern and southern flanks. The Hercynian fold region is buried under Mesozoic and Cenozoic sediments and is further complicated by Laramian and Attic fold-thrust dislocations of lesser intensity. Conclusions. The thrust model brings the geophysical parameters into the correspondence with the geological data and is confirmed by the actual material.

The curse of coal or peripherality? Energy transitions and the socioeconomic transformation of Czech coal mining and post-mining regions

Abstract New empirical evidence regarding theories of the resource curse and regional resilience in the context of energy transitions is presented in this article. Our analysis aimed to answer the questions of what the principal differences are between coal mining and other regions in the Czech Republic, and what are the determinants of population decline, unemployment and populism as some of the key indicators of socioeconomic transformation. Unlike most current European studies focusing on NUTS2 or NUTS3 regions, we deal with data for districts (LAU1). The analysis revealed that (in aggregate) coal mining and post-mining districts are worse off in terms of air quality, population vitality, labour market and social capital indicators. It would be problematic for policy implications to consider coal mining and post-mining districts as homogenous categories, however, since there are significant inter-group and intra-group differences in most indicators. Coal mining itself and its decline did not prove to be a direct determinant of population loss, unemployment, and support for populism. The factors significantly affecting these phenomena are geographical (peripherality, urbanisation, population density) and socioeconomic (education level, business activity). In this respect, a provocative question is offered: to what extent is it effective and sustainable to economically support coal mining regions in their existing industrial production structures and population scales, and whether the current processes of reterritorialisation and depopulation can be considered a natural process. The fact that coal mining districts are at the forefront in the implementation of wind energy may be seen as positive, but it raises questions about spatial concentration, and the environmental justice of renewable energy development.

ISOLATION AND CHARACTERISTICS OF BACTERIA CITROBACTER SP. SR35 FROM A COAL MINE WASTE DUMP

SummaryBacteria of the genus Citrobacter are found in soil, water, the intestinal tract of animals, human clinical samples (urine, sputum, blood, wound drainage, etc.), also in wastewaters and waste dumps of mines. Gram-negative bacteria SR35, capable of reducing sulfur and sulfate ions, were isolated from the waste dump of the Nadiya coal mine, Chervonograd Mining and Industrial district (Lviv region, Ukraine). The work aimed to identify and study morphological, physical and chemical properties (cell shape, size, Gram staining, sporulation, motility, oxygen requirements, ability to form H2S, utilization of carbon sources, catalase activity, oxidase activity) of isolate SR35. Methods. We used standard microbiological and biochemical research methods (microbial culture, microscopy methods, determination of amilase, lipase activity). Chromosomal DNA was isolated by the method of soft lysis. The 16S rRNA gene was amplified using universal primers 27F and 1492R. It was sequenced by the Sanger method. Phylogenetic reconstruction was performed using the MEGA X program. Identification of isolates was carried out based on both the sequence of the 16S rRNA gene and physiological and biochemical properties. Results. The studied bacteria are rods (0.5–0.8×1.5–2.0μm), which form chains and are capable of reducing nitrate and sulfate ions and assimilating several carbon sources. Glucose, lactose, mannose, mannitol, and inositol are fermented with the formation of acid. Motile. Catalase positive, oxidase negative. Form H2S during growth in Kligler’s medium. According to the results of pairwise alignment of the isolate’s 16S rRNA gene sequence, the highest percentage of identity with representatives of the genus Citrobacter was established (99.23–99.86% identity, coverage 98%) and it was confirmed by phylogenetic reconstruction. Citrobacter sp. SR35 is resistant to 2 μM cadmium (II), 5 mM iron (II), 0.25 mM cobalt (II), 10 mM manganese (II), 0.5 mM copper (II), and 0.1 mM chromium (VI). Conclusions. According to the results of sequencing of the 16S rRNA (accession number GenBank OP279754) gene, and physiological, and biochemical characteristics (oxidase, catalase, metabolism of carbon sources, production of H2S, etc.), it was established that isolate SR35 belongs to the genus Citrobacter.

Herbaceous and Woody Root Biomass, Seasonal Changes in Root Turnover, and Arbuscular Mycorrhizal and Ectomycorrhizal Colonization during Primary Succession in Post-Mining Sites

Seasonal changes in the biomass and length of fine roots and their growth into ingrowth cores were measured in a chronosequence of post-mining sites represented by 6-, 16-, 22-, and 45-year-old study sites, located on spoil heaps after brown coal mining in the Sokolov coal mining district. The depth distribution of roots differed between herbs and woody species and also with succession age. At the 22-year-old site, the greatest root biomass was found in the fermentation layer (248.9 ± 113.4 g m2) and decreased with depth. In the case of herbaceous root biomass, the greatest root biomass was found in the 16-year-old site (63.7 ± 15.2 g m2), again in the fermentation layer, which decreased with depth. Overall root biomass increased with succession age, reaching its highest value in the 45-year-old site. In younger sites, the root biomass was dominated by herbs and grasses, whereas woody roots dominated in older sites. After one year, the root biomass in ingrowth cores reached up to one quarter of in situ biomass, which would suggest a low turnover rate. However, the difference between the minimum and the maximum value during the course of one year represents more than half of the mean value. Analysis of the number of arbuscules on roots of Plantago lanceolata sown in soil from all succession stages revealed extensive colonization by arbuscular mycorrhizal fungi in early succession (14.2 ± 0.3 mm root−1), decreasing with succession age, and reaching the lowest value in the 22-year-old site (2.4 ± 0.08 mm root−1) before increasing in the oldest site. Colonization of roots by ectomycorrhizal fungi increased with succession age, reaching a maximum in the 16-year-old site. In comparison with the extent of ectomycorrhizal colonization in relation to root length, the greatest length of ectomycorrhiza-colonized roots was found in the 22-year-old site; hence, the pattern was the opposite of the one observed in arbuscular mycorrhiza-colonized roots.

A dual-continuum model (TOUGH2) for characterizing flow and discharge in a mechanically disrupted sandstone overburden

Underground hard coal mining usually disrupts the mechanical equilibrium of rock sequences, creating fractures within minor permeable rocks. The present study employs a dual-continuum model to assess how both fractured and porous sandstone media influence the percolation process in postmining setups. To test the approach, the software TOUGH2 was employed to simulate laminar fluid flow in the unsaturated zone of the Ibbenbüren Westfield mining area. Compared to other coal mining districts in Germany, this area is delineated by the topography and local geology, leading to a well-defined hydrogeological framework. Results reveal good agreement between the calculated and measured mine water discharge for the years 2008 and 2017. The constructed model was capable of reproducing the bimodal flow behavior of the adit by coupling a permeable fractured continuum with a low-conductivity rock matrix. While flow from the fractured continuum results in intense discharge events during winter months, the rock matrix determines a smooth discharge limb in summer. The study also evaluates the influence of individual and combined model parameters affecting the simulated curve. A detailed sensitivity analysis displayed the absolute and relative permeability function parameters of both continua among the most susceptible variables. However, a strong a priori knowledge of the value ranges for the matrix continuum helps to reduce the model ambiguity. This allowed for calibration of some of the fractured medium parameters for which sparse or variable data were available. However, the inclusion of the transport component and acquisition of more site-specific data is recommended to reduce their uncertainty.

Current stress field and its relationship to tectonism in a coal mining district, central China, for underground coal energy exploration

Adopting 47 sets of in situ stress measurements taken at depths ranging from 417 to 1123 m in a coal mining district in central China by the overcoring method, we characterize the magnitude and orientation of the current stress field and its relationship to tectonism in this district to determine the controls on in situ stress in underground coal energy exploration and seismogeology. The measurements reveal that this district is in a relatively high horizontal stress environment. The stress regimes are generally favorable for strike-slip faulting and reverse faulting and are characterized by σH >σv >σh and σH >σh >σv, revealing that the regional stress field is absolutely dominated by horizontal tectonic stress and reflects a typical tectonic stress field type. The maximum horizontal principal stress is predominantly oriented between the ENE–WSW and WNW–ESE directions and averages nearly E–W,​ which is closely related to the tectonic plate movement and crustal deformation and agrees well with the direction derived from focal mechanism solutions and other stress indicators in and around the region. The current stress field in this district generally inherited the characteristics of the tectonic stress field in the third stage and partially retained the traces generated by the tectonic stress field in the first and second stages. In addition, the frictional parameter μm, which is calculated using the derived stress data, is used as a strong predictor to reflect the capability of the level of crustal stress accumulation. This region is in a state of critical or subcritical equilibrium, and regional faults at shallow depths have a medium to slightly high frictional strength, indicating that some well-oriented faults may theoretically approach or reach frictional equilibrium and that frictional sliding may occur.

Selenium Migration Mode in Coal Seams: Insights from Multivariate Analysis, Leaching Investigation, and Modelling

Processes controlling selenium concentrations ([Se]) in mine waters were studied at an operating coalmine district in Xuzhou city, China. The geochemistry and mobility of selenium was studied through leaching experiments, multivariate analysis, and numerical modeling. Results showed that selenium leaching was influenced by selenium occurrence in minerals, pH, electron activity (pe), and sulfur concentration in the water. Selenium occurrence in host rock was mainly sulfide minerals, and clay minerals in coal, respectively. Therefore, the oxidation and dissolution of sulfide minerals and transformation of clays may control the release of selenium. Experimental leaching experiments suggested selenium tends to leach more when the solution has more sulfur dissolved. A positive relationship is established between pH and the amount of Se released into solution with four times more Se released at pH 12 compared to pH 2 when leached with high-purity water. This release behavior is higher in O2-rich environments. The numerical modeling results showed that pH, pe, and sulfur presence in the solution play important roles in selenium adsorption. Selenium was desorbed from adsorbing surfaces under alkaline conditions, specifically when the solution pH was higher than 8. Higher pe values in the solution caused reduced selenium adsorption. In addition, dissolved sulfur competed with selenate for surfaces of adsorption, thus, selenium adsorption decreases as the sulfur concentration increased.

Pollution of mine and ground water in Shakhtinsky district of Eastern Donbass

The main purpose of this research is to assess the role of coal mines in generation of chemical composition of mine and ground water in the oldest coal-bearing Shakhtinsky district in Eastern Donbass. The standard methods of mathematical and statistical data analysis are used to characterize mine and ground water (estimated arithmetical mean, median estimator, minimum and maximum values, standard deviation). The main index of water contamination is the contamination rate of water, soil, bottom sediments, etc., which is commonly used in geochemistry and geoecology, namely, the pollution load factor and the overall water pollution index. The water quality assessment uses the standards adopted in RF, USA, EU and WHO for drinking and fishery water. The practices of coal mining and mine closure widely use leaching, oxidation and dissolution elements, especially sulphur and sulphides, the content of which in coals and rocks reaches 4-5 %. As a result, mine water becomes highly mineralized and often acidic, and has the highest concentrations of Fe and Mn, hundreds of time higher than MAC in drinking water. Furthermore, it should be noted that MAC is largely exceeded by concentrations of Be, Ni, SO4, Mg and Na. Heavily contaminated ground water in coal-bearing Shakhtinsky district sometimes contain acid water with mineralization up to 15 g/l. The studies show that mine water is the main source of ground water pollution. The high contamination rate of mine and ground water in Shakhtinsky coal mining district necessitates monitoring observations toward improvement of water treatment technologies and environmental reclamation. In the development of mine water treatment technologies, it is necessary, first, to reduce the concentrations of Fe and Mn, as well as Be, Ni, SO4, Mg, and the index of mineralization M.

Hydrogeochemistry and Quality Assessment of Groundwater Based on Fuzzy Analytical Hierarchy Process: A Case Study From Sulin Coal-Mining District in Northern Anhui, China

Hydrogeochemistry and Quality Assessment of Groundwater Based on Fuzzy Analytical Hierarchy Process: A Case Study From Sulin Coal-Mining District in Northern Anhui, China

Geochemical Behaviours and Formation Mechanisms for Elevated Fluoride in the Drinking Groundwater in Sulin Coal-Mining District, Northern Anhui Province, China

Geochemical Behaviours and Formation Mechanisms for Elevated Fluoride in the Drinking Groundwater in Sulin Coal-Mining District, Northern Anhui Province, China

Calculating groundwater mixing ratios in multi-aquifers based on statistical methods: a case study

Abstract Samples of river water and groundwater from Quaternary (QA), sandstone (SA), Taiyuan formation (TA), and Ordovician limestone (OA) aquifers in the Suxian coal-mining district, Anhui Province, China were collected. Their physicochemical properties, and major ion and isotopic compositions were determined. The samples were alkaline, with pH values exceeding 8, and the total dissolved solids concentrations depended on the water source. The δD and δ18O contents were highest in the river water samples and lowest in the SA groundwater. The isotopic characteristics of the QA and OA groundwaters suggest recharge by rainfall and surface water. The isotopic characteristics of river water were controlled mainly by evaporation. Water–rock interactions, the flow rate, and the main water sources were the most important influences on groundwaters in QA, OA, and TA, but the properties of SA groundwater were controlled by static reserves. Two discriminant functions, explaining more than 98.2% of the total variances, indicated that QA, TA, and OA were hydraulically connected. Three groundwater sources were identified as end-members, and a conceptual model was established to calculate water mixing ratios.

Residential Development in the Coal Mining Districts of the Kuznetsk Basin in 1930–1932

The article features the problem of residential development that migrant workers had to face in the mining districts of the Kuznetsk Basin during the first five-year plan. The author identified the causes of the housing crisis in the early 1930s that forced many independent miners to abandon mining enterprises. The paper describes the agenda taken by the central government authorities of Donbass and Kuzbass in order to provide miners with housing. It focuses on the types of housing in the Kuznetsk Coal Basin according to the method of production and building patterns, including communal houses. Prefabricated standard wooden constructions made it possible to build a lot of houses in a relatively short period of time. The main mistakes included a poor material base, limited workforce, and a shortage of building materials. As a result, the initial construction program was never fulfilled. The research focused on the residential development of the coal mining town of Prokopyevsk, its types of dwellings, the number of citizens involved in mining provided with state-owned housing, and the average housing space per capita. Thanks to the housing commissioned, the housing stock was significantly increased in the coal industry in general, and, more particularly, in the Kuzbassugol coal mining trust. The extensive residential development was not aimed at improving the living conditions of miners and their families but at binding migrants to their mines in order to meet the coal-mining program of the first five-year plans.

Groundwater Hydrogeochemical Mechanisms and the Connectivity of Multilayer Aquifers in a Coal Mining Region

Multiple runoff connections for groundwater supply and water quality evolution mechanisms were disclosed using hydrochemistry, multivariate statistics, stable hydrogen and oxygen isotopes, and inverse hydrogeochemical modeling in a multi-layer groundwater system in a north China coal-mining district. Groundwater quality was mainly influenced by dissolution and weathering of carbonate, silicate, gypsum, halite, and fluorite, as well as cation exchange. Sulfate enrichment in the Carboniferous limestone aquifer may be due to pyrite oxidation, while gypsum dissolution and sewage contribute sulfate to the Quaternary alluvium. The Ordovician limestone groundwater is hydraulically connected to the other two aquifers. Incongruent dissolution of dolomite occurs when the Ordovician limestone water contacts the Carboniferous aquifer, while evaporation occurs when the Ordovician limestone water migrates upward through fractures to the Quaternary aquifer.

Perceptions of external costs of dust fallout from gold mine tailings: West Wits Basin

Mining is important for the South African economy, as it is for many developing African nations. In 2017, mining was reported to contribute 6.8 % to the South African GDP and provided more than 460, 000 jobs. Though mining adds an enormous amount of value to the country, it has significant impacts on the environment and the socio-economic factors of society. The well-documented environmental impact of mining operations on surface and groundwater systems, known as Acid Mine Drainage (AMD), is just one of these environmental impacts. There are also other impacts such as the pollution of agricultural soils, the creation of sinkholes and air pollution. For example, airborne dust remains a persistent problem in South African urban areas due to the climatic conditions, extensive surface mining, unrehabilitated tailings storage facilities and mineral processing. However, very little is reported on the socio-economic costs that are due to poor environmental management. Some scholars assert that despite the Mine Health and Safety Act, deposition monitoring guidelines and national dust regulations, South Africa still experiences persistent dust problems, especially in coal and gold mining districts. This paper investigates the effect of gold mining dust pollution in and around a Gold Mining Village, in South Africa. A quantitative and qualitative approach was used, where a questionnaire and interviews were conducted to examine the Gold Mine Village perceptions on dust pollution and their socio-economic environment. This paper further examines how poor and premature mine closure by liquidation results in unrehabilitated mine tailings and how this has significant impacts on the socio-economic status of individuals and surrounding businesses. The community being investigated in this study, perceives the dust fallout impact to be a socio-economic threat. The paper finds that the community believes it incurs medical financial expenditures due to treating respiratory-related diseases triggered by dust fallout.

Depressions caused by localized subsidence in the Netherlands, Belgium and Germany: a link with coal mining?

Abstract. In the coal mining districts of the Netherlands, Belgium and Germany, we identified 662 previously unidentified depressions at the land surface using LIDAR data. Their density decreases westwards along with deepening of the Carboniferous coal layers, while not changing in dimensions. The timing of their formation based on historical maps and landowner reports, suggests that they mostly formed during the period 1920–1970, the peak of mining activity. Based on their position, density and age, we link the formation of depressions to the coal-mining activities in South Limburg, Germany and Belgium. Our working hypothesis tentatively explains the origin, mechanism of formation and timing of these local subsidence features.

Groundwater chemical characteristics and circulation mode in the Suixiao coal-mining district

Groundwater recharge and runoff conditions are ascertained in the Suixiao coal-mining district using the hydrogen and oxygen isotopes and the trace elements in the unconsolidated pore aquifer of the Cenozoic group, the fissured sandstone aquifer of the Permian system, and the karst fissured limestone aquifer of the Carboniferous Taiyuan Formation and the Ordovician system, which are the main recharge aquifers during coal mining. The main water–rock interactions are pyrite oxidation, cation exchange and adsorption, and carbonate acidification, which are educed by principal component analysis of conventional ions. These results combined with geological conditions prove that hydraulic connection exists generally between the main recharge aquifers, and the groundwater circulation is controlled by faults in the sandstone and limestone aquifers. The water–rock interaction is very weak in the east of the district, which is proved to be a recharge area by Fisher discriminant analysis. This study provides the theoretical basis for the hydrochemistry exploration and the establishment of a water-inrush warning system in a concealed coalfield.

Evaluation of treatment efficiency of coal mine drainage and impact on surrounding waters for selected coal mines

Coal mine water usually has high content of trace elements, leading to contamination of surrounding water bodies. Water treatment technologies are used to remove organic and inorganic matters from coal mine water. To evaluate the treating efficiency of conventional and advanced treatment on coal mine drainage, samples of coal mine, carbonate, surface water, and treated water from the treatment processes were collected and analysed. It turns out that the conventional treatment processes can hardly remove both major ions and trace elements in coal mine water. Reverse osmosis technology can reject major ions effectively, but weak in trace elements removal. The analysis of surface water quality suggested contamination by coal mine water in the coal-mine district. To control the contamination and reuse the coal mine water effectively and safe, it is necessary to evaluate more carefully the efficiency of water treatment and potential environment impact of coal mine water on the surrounding surface and ground waters.

The Occurrence and Concentration of Rare Earth Elements in Acid Mine Drainage and Treatment By-products: Part 1—Initial Survey of the Northern Appalachian Coal Basin

The conventional rare earth element (REE) industry has historically sought to develop ore deposits where geologic processes have produced mineralized zones with commercially attractive REE concentrations. These deposits are extremely uncommon, particularly in the USA. Given the criticality of these materials and the need for sustainable domestic supply, the current research seeks to leverage other autogenous processes that lead to concentrated REE resources. One such process is the generation of acid mine drainage (AMD). AMD is very common in many coal mining districts and results from the exposure and oxidation of pyrite during mining. During the generation and migration of AMD, liberated sulfuric acid mobilizes several metal ions including REEs. Treatment of AMD is required under U.S.C §1251, the Clean Water Act, and often consists of neutralization, oxidation, and metal hydroxide precipitation. To investigate the deportment of REEs during this process, a field sampling campaign was undertaken, whereby the concentration of REEs in AMD and AMD precipitates was measured directly. In the nine sites evaluated in this study, the REE concentrations of the precipitates varied from 29 to 1286 ppm with an average of 517 ppm among the sampled sites. The individual elements were enriched compared with the associated bulk Northern Appalachian (NAPP) coal material by factors ranging from 3 to 15. Furthermore, the distribution of REEs in all precipitate samples favored the heavy REEs (HREEs) when compared with traditional REE ores. This research represents the first part of multi-part research endeavor to characterize, classify, and determine the practicality of refining REEs from AMD and its by-products.

Effects of mining speed on the developmental features of mining-induced ground fissures

Shallow coal seam exploitation not only causes serious surface subsidence but also induces extensive ground fissures, which severely threaten the safety of underground mining and the surface eco-environment. We use the Daliuta coal mine of the Shendong mining district in China as a case study to investigate and characterize the influence of underground coal mining on the development of ground fissures. A new comprehensive impact parameter K of geology and mining for ground fissure development is introduced to explain the effects of mining speed on the developmental features of ground fissures. The results show that ground fissures often develop in the surface tensile zone ahead of the working face advancing position and show an inverted C-shape on the surface, which is similar to periodic fracturing of the basic roof. The ground fissure angle increases linearly with mining speed and logarithmically with K, while the developmental cycle decreases linearly with mining speed. We propose a technical measure to control ground fissure disasters by adjusting mining speed, which provides a theoretical reference for eco-environmental governance in shallow coal seam mining districts.