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In order to explore the mechanical response characteristics of faults when the working face is normal fault mining, a numerical simulation model is established based on the engineering geological conditions of 1105 working face in Gaozhuang Coal Mine to obtain the evolution characteristics of fault damage variables under mining disturbance. The simulation results are analyzed by multiple linear regression analysis and the mechanical model of footwall rock mass is established to obtain the relationship between fault damage variables and coal stress. The results show that the fracture damage of the fault develops from the high rock layer to the low rock layer. When the fault damage variable reaches the critical value, the fault has the condition to activate; under the influence of working face mining, the development of fault damage variable is earlier than the increase of abutment pressure of coal body. Fault damage variable can be used as a key index to predict fault activation and coal body stress increase; through multiple linear regression analysis, the determined influencing factors of fault damage variables are distance from fault, vertical stress, internal friction angle of fault and fault cohesion; in the process of working face to fault mining, the decrease of coal width between working face and fault causes the increase of coal stress. At the same time, the mining leads to the damage development of the fault surface, the effective bearing area between the upper and lower rock mass is reduced, the weight of the rock mass is mostly borne by the lower coal body, and the coal body stress is further increased.

Abstract A 3D geometric model is established based on a fluid‒solid coupling model for purpose of identifying the influences of mining disturbances on the distribution of gas pressures in front of a working face during gas extraction. Then, the stress distribution and gas extraction process are simulated using COMSOL software. The spatiotemporal evolutions of gas pressures in front of the working face are analyzed from the dimensions of point, line, surface, and volume. A comparative analysis has been conducted to explore the distribution patterns of gas pressure in fractures and pores. The results show that under mining disturbance, the stresses in front of the working face create a stress-relaxation area, a stress concentration area, and an original stress area. Moreover, a low stress concentration is located near the boreholes. In the early stage of gas extraction, corresponding to the stress distribution, the gas pressures present a depressurization area, pressure concentration area, and almost undisturbed area. As the time increases after mining, the effects of mining disturbances gradually decrease, and the range of the gas pressure concentration area steadily shortens and shifts toward the front of the working face. Under the same temporal conditions, the gas pressure in pores is higher than that in fractures. At the onset of mining, the pore gas pressure is even greater than the initial pressure. Furthermore, during the identical extraction period, the “concentration area” of pore gas pressure is situated farther away from the coal wall of the working face compared to the “concentration area” of fracture gas pressure. These results of the study provide theoretical support for arranging drainage boreholes, enhancing gas extraction efficiency, safeguarding against gas accidents.

Abstract During coal mining operations, the coal will be deformed and damaged due to multiple mining disturbances (MMD), often resulting in disasters, like rock burst. To understand the evolution rules of coal deformation under MMD and its final fracture characteristics after impact dynamic load loading, reduce the adverse effects of mining disturbances, and improve disaster prevention and control capabilities, quasi-static uniaxial cyclic loading-unloading (L-U) and dynamic axial compression tests were conducted on large-sized coal-like samples. During the tests, three-dimensional (3D) laser scanning and acoustic emission (AE) monitoring technology were utilized to accurately capture the full-field deformation and AE response data, facilitating a systematic analysis of deformation and fracture characteristics. The results show that: (1) Under the cyclic L-U effect induced by MMD, each loading cycle causes compression deformation with partial recovery during unloading, presenting an overall “wavy” variation trend. (2) The maximum load is the most critical factor affecting the damaged coal deformation, with smaller load resulting in less overall sample deformation. (3) After the impact dynamic loading, the damaged samples suffered large-scale impact splitting failure, with the compressive-shear layer failure mainly occurred inside the holes. (4) Lower loading during cyclic L-U process correlate with reduced damage degree, and smaller debris particles with a higher fractal dimension when impact failure occurs, indicating a more severe impact failure. (5) With multiple cycles of L-U, the cracks inside the sample gradually extend and expand from around the hole to the outside. The greater the load and the number of cycles, the more serious the crack damage will be. (6) In the practical mining process, it is crucial to reinforce roadway interiors while minimizing low-loading cyclic disturbances induced by MMD. The study has obtained the deformation evolution rules and failure characteristics of coal under MMD, providing a theoretical basis for the prevention and control of corresponding engineering disasters.

Abstract To solve the problem of controlling the stability of small coal pillars under the mining disturbance of the adjacent working face, the fourth panel 403 and 404 working faces of the Gaojiabao coal mine with two mining roadways is taken as the object of this research. The comprehensive research method of combining mechanical theory analysis, coal dynamic disturbance experiments and field engineering practice was adopted. First, the analysis determined the magnitude and frequency of fracture‐related disturbance loading on the overburden roof of the working face; next, the strain and stress threshold indicators of the coal body, sensitive to the external disturbance load of 103 J magnitude (continuous disturbance deformation), were tested and obtained through a self‐developed rock creep disturbance experimental system, and the stress threshold indicators of coal body specimens sensitive to creep disturbance were defined as the long‐term strength. Then, a coal pillar‐roof mechanics structure model was established in the premining and postmining areas of the working face, and the overlying support pressure on the coal pillar body was analysed. Finally, a small coal pillar composite reinforcement support technology with ‘two‐way buttressing anchor cable for pressure reinforcement + steel pipe concrete pier column + overhead roof break’ was designed to ensuring that the coal pillar body would not be destabilised by cumulative disturbance and large deformation under disturbance. According postmining area support capacity calculations, the support loading acting on the coal pillar is approximately 17593 kN, with the stress being 2.93 MPa; and the factor of safety is approximately 1.23. After engineering practice application of this approach, the vertical deformation of the small coal pillar body and side heave disturbance deformation were effectively controlled during the working face mining disturbance, the vertical deformation of the reinforced coal pillar was only 187 mm, and the side heave deformation was finally stabilised at approximately 124 mm, which maintained good stability.

Rockburst, one of the leading types of disaster in mining and rock engineering causing serious injuries and the loss of property, frequently occurs, involving various features and complex evolutionary mechanisms. Compared to rockbursts occurring at mining faces, those occurring in main roadways cause more serious problems for mine production. This paper first analyzes the characteristics of rockbursts in main roadways using two case studies involving the Gaojiapu and Cuimu coal mines. The causes of rockbursts in main roadways were studied using microseismic monitoring, energy density cloud maps, and seismic velocity tomography. During the mining of the 22306 working face in the Cuimu coal mine, targeted measures, such as deep-hole blasting of the roof strata and deep-hole blasting of the coal seam, were implemented to prevent rockbursts in the main roadways. The effectiveness of these measures was verified through long-term analysis of tremor activities. The study found that the influence of mining at two working faces on both sides of main roadways was significantly greater than that from a single-sided working face. The intensity of the tremor activities occurring near the main roadways was correlated with the distance from the working face to the main roadways. The closer the working face was to the main roadways, the stronger the tremor activities were near the main roadways. According to the distribution range of the tremors, the influence area of working face mining exceeded 800 m, with tremors distributed linearly along the main roadways. Even five months after the completion of working face mining, there were still a large number of tremors near the main roadways, which gradually disappeared after another five months. Mining activities were the main reason for the occurrence of main roadway rockbursts and the stress concentration within the main roadways themselves was another reason for the occurrence of rockbursts. The influence of working face mining could be reduced by deep-hole blasting of roof strata and the stress concentration within main roadways themselves could be reduced by large-diameter drilling. Those joint preventive measures effectively prevented the occurrence of rockbursts in main roadways. This study is of important theoretical and practical significance for further studies of rockburst mechanisms and prevention in regard to main roadways in coal mines, and the findings are significant in terms of the enhancement of safety in coal mines. [ABSTRACT FROM AUTHOR]

During coal mining operations, the coal will be deformed and damaged due to multiple mining disturbances (MMD), often resulting in disasters, like rock burst. To understand the evolution rules of coal deformation under MMD and its final fracture characteristics after impact dynamic load loading, reduce the adverse effects of mining disturbances, and improve disaster prevention and control capabilities, quasi-static uniaxial cyclic loading-unloading (L-U) and dynamic axial compression tests were conducted on large-sized coal-like samples. During the tests, three-dimensional (3D) laser scanning and acoustic emission (AE) monitoring technology were utilized to accurately capture the full-field deformation and AE response data, facilitating a systematic analysis of deformation and fracture characteristics. The results show that: (1) Under the cyclic L-U effect induced by MMD, each loading cycle causes compression deformation with partial recovery during unloading, presenting an overall "wavy" variation trend. (2) The maximum load is the most critical factor affecting the damaged coal deformation, with smaller load resulting in less overall sample deformation. (3) After the impact dynamic loading, the damaged samples suffered large-scale impact splitting failure, with the compressive-shear layer failure mainly occurred inside the holes. (4) Lower loading during cyclic L-U process correlate with reduced damage degree, and smaller debris particles with a higher fractal dimension when impact failure occurs, indicating a more severe impact failure. (5) With multiple cycles of L-U, the cracks inside the sample gradually extend and expand from around the hole to the outside. The greater the load and the number of cycles, the more serious the crack damage will be. (6) In the practical mining process, it is crucial to reinforce roadway interiors while minimizing low-loading cyclic disturbances induced by MMD. The study has obtained the deformation evolution rules and failure characteristics of coal under MMD, providing a theoretical basis for the prevention and control of corresponding engineering disasters. [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To solve the problem of controlling the stability of small coal pillars under the mining disturbance of the adjacent working face, the fourth panel 403 and 404 working faces of the Gaojiabao coal mine with two mining roadways is taken as the object of this research. The comprehensive research method of combining mechanical theory analysis, coal dynamic disturbance experiments and field engineering practice was adopted. First, the analysis determined the magnitude and frequency of fracture‐related disturbance loading on the overburden roof of the working face; next, the strain and stress threshold indicators of the coal body, sensitive to the external disturbance load of 103 J magnitude (continuous disturbance deformation), were tested and obtained through a self‐developed rock creep disturbance experimental system, and the stress threshold indicators of coal body specimens sensitive to creep disturbance were defined as the long‐term strength. Then, a coal pillar‐roof mechanics structure model was established in the premining and postmining areas of the working face, and the overlying support pressure on the coal pillar body was analysed. Finally, a small coal pillar composite reinforcement support technology with 'two‐way buttressing anchor cable for pressure reinforcement + steel pipe concrete pier column + overhead roof break' was designed to ensuring that the coal pillar body would not be destabilised by cumulative disturbance and large deformation under disturbance. According postmining area support capacity calculations, the support loading acting on the coal pillar is approximately 17593 kN, with the stress being 2.93 MPa; and the factor of safety is approximately 1.23. After engineering practice application of this approach, the vertical deformation of the small coal pillar body and side heave disturbance deformation were effectively controlled during the working face mining disturbance, the vertical deformation of the reinforced coal pillar was only 187 mm, and the side heave deformation was finally stabilised at approximately 124 mm, which maintained good stability. [ABSTRACT FROM AUTHOR]

Mining disturbance has great impacts on soil physicochemical factors, causing notable differences between pre-mining and after-mining conditions, and between coal mining areas and non-mined areas. However, little is known about whether the fissure statuses induced by mining activities affect the edaphic factors and how soil microbial communities respond to these fissure development states. In this study, we systematically investigated the edaphic factors and microbial communities in a mining disturbance area exhibiting the full development status of soil fissures, where the sampling sites were divided into soil fissure development and closure zones. Microbial alpha-and betadiversity, correlation coefficient matrix, non-metric multi-dimensional scaling, principal co-ordinates analysis, mantel test, and microbial co-occurrence network were employed to elucidate variations, correlations, and interactions between edaphic factors and microbial communities under the two different soil fissure states. Results suggested that soil physicochemical properties were significantly affected by fissure states, showing an increasing trend in soil moisture content and soil nutrients. The associations among edaphic factors have weakened during the soil fissure development process. Soil microbial communities showed different compositions and the underlying influential mechanisms between two soil fissure states. Soil moisture content, pH, particle compositions, organic matter, and heavy metals largely affected microbial communities. Rare species were vulnerable to mining disturbance and were keystone taxa that reinforced the overall interconnections of the soil microbial community (e.g., Nordella, Sphingomonas, Massilia, and Rubritepida). Our study revealed the impacts of distinct fissure states on the soil physicochemical properties and microbial communities, and the edaphic conditions showed key contributions to the soil microbial communities, particularly the abundance and ecological roles of rare species. [ABSTRACT FROM AUTHOR]

The ore (rock) bodies between the 570 m and 630 m levels in Jiaojia Gold Mine are characterized by well-developed joints and fissures, prone to forming wedge-shaped unstable structures, leading to rock mass col- lapse. Geological drilling and structural surface condition surveys indicate that the rock mass in Jiaojia Gold Mine is relatively fractured, with well-developed joints and a wide range of joint occurrence distributions. This study investi- gates and summarizes the convergence deformation patterns of roadways under mining disturbances. Radar testing and analysis reveal that the damage depth of the roadways in Jiaojia Gold Mine generally remains at about 2 m, with many weak structural surfaces present, necessitating timely reinforcement measures. This research provides a rational plan for the support of the ore body and guides the reasonable selection of stope structural parameters to ensure safe production in this mining section. It offers valuable insights for managing fractured rock mass in similar mines. [ABSTRACT FROM AUTHOR]

Copyright of Mining & Metallurgy (10057854) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The mechanical behavior of the coal body acted upon by varying pressure is very important for the stability analysis of the actual mining face. Based on the designed stress loading path, uniaxial compression tests are performed on coal samples of different coal steps in the presence of various loading rates. The main goal of this investigation is to examine the internal damage and crack evolution characteristics of the coal samples. The results reveal that the ringing number and energy abruptly alter before the peak stress, the resistivity decreases, the damage increases and the internal fracture development of the coal rock intensifies. The low-order coal is essentially damaged in shear after several stages of loading, and the high-order coal is mainly damaged in tension due to the stress concentration caused by the primary cracks, and the fracture rapidly develops along the primary cracks. The obtained results of this study provide a theoretical basis for the design of the protective layer and the control of mining disturbances in the actual working face mining environment. Highlights: Development of an approach of mining disturbed stress loading rate. Assessment of mechanical properties of various coal rank samples subjected to mining disturbed stress environment. Loading rate variations cause sudden changes in the coal rock ringing number, energy, resistivity, and damage. Characteristics of fracture evolution of various coal rank samples during the loading process. [ABSTRACT FROM AUTHOR]

Copyright of China Mining Magazine is the property of China Mining Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to disclose the multi-physical field characteristics of the deep coal seam mining process and their dynamic evolution legislation, based on the "rock-coal-rock" model, during the mining process, the stress field, displacement field, energy field, and plastic zone evolution process are all simulated using FLAC3D6.0. The findings show that stress in the original rock is redistributed as a result of coal seam mining, creating a pressure relief zone in the middle of the goaf and advanced support pressure in the front part of the working face. The roof falls following the termination of coal seam mining. The collapsed blocks fill the middle of the goaf, playing a supporting role. The floor bulges as a new supporting pressure zone forms and builds up high elasticity. The stress reduction zone shifts from a rectangular to an inner circular distribution and an outer square as the working face's mining distance increases and the range of the fracture field expands accordingly. In addition, a complete model was constructed to verify the correctness of the "rock-coal-rock" model. The stress, displacement, and energy curves of the overlying strata at a distance of 12 m from the bottom of the coal seam in the middle of the goaf obtained by the two methods were basically consistent. Ultimately, the findings of the numerical simulation were compared with the advanced support pressure data that were acquired on-site and they were good. This work can provide a reference for the safe mining of deep coal seams. [ABSTRACT FROM AUTHOR]

Rockburst, one of the leading types of disaster in mining and rock engineering causing serious injuries and the loss of property, frequently occurs, involving various features and complex evolutionary mechanisms. Compared to rockbursts occurring at mining faces, those occurring in main roadways cause more serious problems for mine production. This paper first analyzes the characteristics of rockbursts in main roadways using two case studies involving the Gaojiapu and Cuimu coal mines. The causes of rockbursts in main roadways were studied using microseismic monitoring, energy density cloud maps, and seismic velocity tomography. During the mining of the 22306 working face in the Cuimu coal mine, targeted measures, such as deep-hole blasting of the roof strata and deep-hole blasting of the coal seam, were implemented to prevent rockbursts in the main roadways. The effectiveness of these measures was verified through long-term analysis of tremor activities. The study found that the influence of mining at two working faces on both sides of main roadways was significantly greater than that from a single-sided working face. The intensity of the tremor activities occurring near the main roadways was correlated with the distance from the working face to the main roadways. The closer the working face was to the main roadways, the stronger the tremor activities were near the main roadways. According to the distribution range of the tremors, the influence area of working face mining exceeded 800 m, with tremors distributed linearly along the main roadways. Even five months after the completion of working face mining, there were still a large number of tremors near the main roadways, which gradually disappeared after another five months. Mining activities were the main reason for the occurrence of main roadway rockbursts and the stress concentration within the main roadways themselves was another reason for the occurrence of rockbursts. The influence of working face mining could be reduced by deep-hole blasting of roof strata and the stress concentration within main roadways themselves could be reduced by large-diameter drilling. Those joint preventive measures effectively prevented the occurrence of rockbursts in main roadways. This study is of important theoretical and practical significance for further studies of rockburst mechanisms and prevention in regard to main roadways in coal mines, and the findings are significant in terms of the enhancement of safety in coal mines.

Under the influence of mining activities, investigating hydrological processes is an important cornerstone of water resources and eco-environment protection. In this study, the spatio-temporal variations of stable isotopic compositions (δD and δ18O) of river water and groundwater in five periods of a hydrological year were analyzed to identify the origin and hydraulic connection of water bodies in the mining district under mining disturbance. The δD and δ18O indicate that the water bodies in the study area are mainly recharged by local precipitation and undergo evaporation. There is a close hydraulic connection between river water, mine water, and groundwater, and the deep confined water is affected by the river water and phreatic water due to the developing water-conducting fractures. The δ18O of phreatic water in each period is depleted in the southwest and enriched in the northeast of the study area. The δ18O of confined water has an obvious spatial variation in the wet season due to the combined effects of opencast working and underground mining, whereas uniform spatial variation is observed in the dry season. Compared with the dry season, mining disturbances have a greater impact on river water and groundwater in the wet season. The difference in spatial variation of δ18O between phreatic and confined water may be attributed to the easier recovery of phreatic water than confined water after mining disturbance. This finding provides important information about the hydrological characteristics of the Pingshuo mining district.

The Ordovician thermal reservoir in Liaocheng East Thermal Field is the preferred area for exploration and development of bedrock thermal reservoir in Shandong Province. In this paper, a regional deep-circulation fracture-karst bedrock thermal reservoir model of semi-structural trap is established by analyzing the geothermal characteristics of caprock, reservoir,water source, heat source and channel in the area. The analysis shows that the semi-trap deep circulation occurrence characteristics not only improve the hot water mineralization and trace elements, but also lead to the problems of strong reservoir sealing, large mining disturbance and difficult sustainable utilization.Based on the measured data of the observation wells in the area for many years, the empirical formula of mining depth reduction is established. The variation coefficient method and comprehensive index method are used to evaluate the disturbance of thermal reservoir mining in the area. It is considered that the exploitation of bedrock thermal reservoir in the area leads to the decrease of water level, water volume, reservoir pressure, temperature and service life. There are few secondary problems such as disturbance of water quality, land subsidence, thermal pollution, environmental pollution and cross-layer water source pollution. Combined with the regional reinjection test, the suitable local mining and reinjection schemes are discussed : centralized mining, gradient utilization, reinjection in the same layer, balanced mining and reinjection. The reinjection wells of bedrock thermal reservoirs in the area should be set in the range of 300-500 m around the mining well, and the tail water temperature should be 35-40 °C. This study provides a theoretical basis for the sustainable utilization of bedrock thermal reservoirs in the area. [ABSTRACT FROM AUTHOR]

Disturbances caused by block caving mining can significantly change the geometric parameters of rock fractures and affect the hydraulic characteristics of the rock mass. In areas with heavy rainfall, there is a high risk of water gushing into mining roadways if the overlying rock mass becomes highly permeable. Therefore, it is extremely important to find out the changes in permeability characteristics of surrounding rock mass under caving mining disturbance. In this research, fracture parameters, including fracture orientation, aperture, density, and trace length, before and after mining activities, were obtained via fracture mapping. Discrete fracture networks were established based on these fracture parameters using the Monte Carlo method, and then seepage simulations were carried out with a MATLAB program. The variations of permeability characteristics of rock mass under block caving mining disturbance, including representative elementary volume for permeability (REV-P), principal permeability direction, and principal permeability coefficients, were obtained. Results show that this seepage simulation method can accurately calculate the permeability coefficients, compared with field test results. After mining disturbance, the mean trace length of fractures and REV-P size increase by about 40%; the principal permeability direction changes from 164.53 to 143.63°, and the maximum principal permeability coefficient increases by 6.6 times, which is mainly influenced by the changes of fracture trace length and aperture due to block caving mining disturbance. [ABSTRACT FROM AUTHOR]

A fault is a common geological structure encountered in underground coal mining. Interactions between the discontinuous structure of a fault and mining activities are the key factors in controlling the rock bursts induced by the fault. It is of great importance to study the rock burst mechanism of an extra-thick coal seam under the combined influence of reverse faults and coal mining for the prediction and prevention of rock burst. In this study, we establish a sliding dynamics model of rock mass in a fault zone and analyze the mechanical distribution of fault-induced rock bursts under the combined action of mining disturbances. Additionally, we utilize theoretical calculation and a 3D numerical simulation method to clarify the rockburst mechanism in an extra-thick coal seam controlled by a thrust fault under mining disturbance and a fault. The results showed that the distribution range of the shear stress increment in the fault footwall was larger than that in the hanging wall, revealing a skewed distribution. The fault dip angle and mining thickness exhibit significant influence on the structure around the fault. With increases in the dip angle of the fault and mining thickness, the maximum vertical stress and peak stress first increase and then decrease. A position 80 m away from the fault is the dividing line between the fault-non-affected area and the fault-affected area. The 13,200 working face of the Gengcun coal mine is used as a case study to study the influence of mining disturbances on microseismic events. The results of this study are in good agreement with the theoretical calculations and numerical simulation results. [ABSTRACT FROM AUTHOR]

Open-pit mining activities inevitably affect the surrounding ecological environment. Therefore, it is crucial to clarify the disturbance characteristics of open-pit mining activities on the surrounding vegetation and scientifically implement ecological restoration projects. This study investigates the impact of open-pit coal mining in arid and semi-arid regions on surrounding vegetation from a vegetation phenology perspective. Initially, we construct a high-frequency time series of vegetation indices by Harmonized Landsat 8 and Sentinel-2 surface reflectance dataset (HLS). These time series are then fitted using the Double Logistic and Asymmetric Gaussian methods. Subsequently, we quantify three pivotal phenological phases: Start of Season (SOS), End of Season (EOS), and Length of Season (LOS) from the fitted time series. Finally, utilizing mine boundaries as spatial units, we create a buffer zone of 100 m increments to statistically analyze changes in phenological phases. The results reveal an exponential variation in vegetation phenological metrics with increasing distance from the mining areas of Heidaigou-Haerwusu (HDG-HEWS), Mengxiang (MX), and Xingda (XD) in northwest China. Then, we propose a method to identify the disturbance range. HDG-HEWS, MX, and XD mining areas exhibit disturbance ranges of 1485.39 m, 1571.47 m, and 671.92 m for SOS, and 816.72 m, 824.73 m, and 468.92 m for EOS, respectively. Mineral dust is one of the primary factors for the difference in the disturbance range. The HDG-HEWS mining area exhibits the most significant disruption to vegetation phenological metrics, resulting in a delay of 6.4 ± 3.4 days in SOS, an advancement of 4.3 ± 3.9 days in the EOS, and a shortening of 6.7 ± 3.5 days in the LOS. Furthermore, the overlapping disturbance zones of the two mining areas exacerbate the impact on phenological metrics, with disturbance intensities for SOS, EOS, and LOS being 1.38, 1.20, and 1.33 times those caused by a single mining area. These research results are expected to provide a reference for the formulation of dust suppression measures and ecological restoration plans for open-pit mining areas. [ABSTRACT FROM AUTHOR]

The rock burst induced by the mutual disturbance of mining and excavation is significantly influenced by high static load stress and external dynamic load disturbance. In this paper, the evolution characteristics and progressive damage mechanism of surrounding rock in the process of mutual disturbance of mining and excavation are systematically studied. The results show that the evolution of surrounding rock stress can be roughly divided into three stages: rapid rise in the early stage, continuous rise and step-like decline in the middle stage, and slow rise in the late stage. In the process of parallel mining, the overlying rock movement above the goaf shows the sequence of horizontal penetration of tiny fissures—fracture intensification transition to stratification—non-coordinated caving of middle–low overlying rock—obvious horizontal cracks in the upper key layer. Only under the quasi-static loading mining action does the upper key layer not reach the breaking condition. The wave side of the heading face which is close to the focal point is affected by the dynamic load disturbance, the acceleration duration is short, and the attenuation is relatively fast, so it is the area prone to the earliest impact failure in the face of mining disturbance. The conclusion is helpful to deepen the understanding of the coal burst mechanism of mutual disturbance of mining and excavation. [ABSTRACT FROM AUTHOR]

Abstract To address the problem of instability and failure of the 11,514 return air roadway caused by dynamic pressure in Jinhuagong Coal Mine, this study uses theoretical analysis, numerical simulation, and field test methods. The disturbance deformation mechanism and the surrounding rock control technology for the 11,514 return air roadway during face‐to‐face mining and excavation are analyzed. The results show that the causes of regional asymmetric deformation and failure of the surrounding rock of the 11,514 return air roadway are multiple superpositions of lateral bearing pressure of the 11,812 mined‐out area, mining stress in the 8814 working face, and advanced stress of the 11,514 return air roadway. When mining and excavation faces meet, the 11,514 return air roadway is affected by the superimposition of the mining stress. At the same time, the solid coal side of the roadway is in the mining pressure relief area in the 8814 working face in the upper coal seam, and the asymmetric distribution of the principal stress on both sides of the 11,514 return air roadway causes deformation and failure of the surrounding rock. Based on the differences in superimposed stress disturbance in different parts of the roadway, a subsection control technology is proposed. This technology is focused on supporting secondary reinforcement in the range of 40 m before and after the mining overlap position on the 11,514 roadway. Field measurement data confirm the effectiveness of this support technology.

Ion-adsorption rare earth mining areas are located in southern China's ecologically fragile red soil hills region. For a long time, under the influence of multiple factors such as low mining technology and indiscriminate mining, this area has experienced serious environmental problems. Therefore, it is crucial for the ecological management and restoration of mining areas to accurately conduct a quantitative evaluation of ecological restoration status. We used remote sensing and geographic information data to establish an ecosystem resilience evaluation index system consisting of five criteria (land stress, vegetation conditions, surface conditions, biodiversity, and air pollution) and 17 evaluation factors. The Lingbei rare earth mining area in Dingnan County in the red soil hill region was used as a case study since it is a representative ion adsorption rare earth mining area. The restoration status of the mining area was evaluated from 2000 to 2020. The results showed the following: (1) From 2000 to 2020, the ecological resilience level of the mining area was 0.695, 0.685, 0.664, 0.651, and 0.657, exhibiting a decrease followed by an increase. (2) Spatially, the ecological resilience was low at the mine site and increased with increasing distance, indicating that rare earth mining adversely affected ecological resilience in the mining area. (3) The regional ecological resilience has improved over time due to the implementation of green development policies. However, the rate of improvement is slow and ecological restoration of mining areas will remain an ongoing challenge in the future. This study can provide a scientific basis and practical reference for the ecological protection and restoration of mining areas. [ABSTRACT FROM AUTHOR]

Overburden strata fracture evolution is critical to dynamic disaster prevention and gas-relief drainage, so it is important to accurately determine the evolution relationships with mining disturbance. In this paper, experiments and numerical simulation were adopted jointly to characterize the time-varying fracture area of overlying strata. The experimental results showed that the roof strata gradually broke and collapsed with coal mining, which indicated the fractures of overburden strata developed in an upward direction. The fracture development causes were explained by numerical simulation, which showed that stress increase exceeded the strength of coal and rock strata, and fractures were formed and expanded. Both experiments and numerical simulation results showed the two sides and the top of fracture areas provided channels and spaces for gas migration and reservoir, respectively. In addition, the breaking angle of overburden strata and the height of fracture areas were analyzed quantitatively. Through microseismic monitoring at the mining site, the fracture scales and ranges of overburden strata were verified by the energy and frequency of microseismic events, which were consistent with the support of maximum resistance. The position of drainage boreholes was considered based on the results of overburden strata fracture evolution. Our study is aimed at promoting coal mining in safety and improving gas drainage with a sustainable approach. [ABSTRACT FROM AUTHOR]

The mining of ion-adsorption rare-earth elements (REE) in South China has caused severe ecological disturbances in mining areas. Therefore, environmental monitoring and evaluation of REE mining areas have become a prerequisite for the sustainable development of the ion-adsorption REE industry. In this study, a remote sensing-based ecological index (RSEI) model was used to evaluate changes in the environmental quality of REE mining areas. Thirty Landsat images from 1986 to 2019 were used in a case study of the Lingbei mining area in Dingnan County, China. Google Earth images were used for visual interpretation and comparison with the classification results of different types of land damage and restoration for different disturbance levels. The random forest (RF) method was used for classification, and the underlying mechanism of the environmental changes was discussed. The results show that the RSEI accurately reflects the environmental quality of the REE mining areas. The analysis of the spatiotemporal distribution of the environmental quality in the REE mining areas shows that since 1986, mining techniques, such as pool leaching, heap leaching, and in-situ leaching, resulted in surface vegetation removal and topsoil stripping, causing extensive environmental damage. After 2011, the environmental quality was slowly restored due to the optimization of mining technology and the government’s focus on environmental management, resulting in the recovery of mining sites. The changes in the environmental quality of the REE mining areas in different disturbance states indicate that the area affected by human disturbance is 15.44 km², accounting for 44.43% of the total mining area and 16.31% of the area exhibits serious impacts on the ecological environment. The proposed method provides a quantitative approach to describe the evolution of environmental quality in the mining area over the past 34 years, providing a scientific basis for the sound management of the mining areas to promote the regional sustainable development. [ABSTRACT FROM AUTHOR]

The roof of the large cross-section roadway under the short goaf area is disturbed by coal seam mining and roadway boring twice, in order to study this two influences, taking the II 8224 open-off cut roadway in Renlou coal mine as the engineering background, the influence depth of goaf unloading and the disturbance characteristics of roadway mining were analyzed by theoretical analysis, numerical simulation and field measurement. The results show that the theoretical calculation results and numerical simulation results of unloading depth in goaf are consistent with the analysis results of drilling core, and the rock strata within the scope of unloading influence will rise up. The subsidence time of large section roadway roof under goaf is 14 d, and the maximum subsidence velocity is only 15 mm/ d. It is concluded that the influence depth of disturbance and failure of upper goaf unloading on floor rock is 5. 2 m. Under the influence of goaf unloading, the subsidence time, subsidence speed and subsidence amount of roadway roof are small. [ABSTRACT FROM AUTHOR]

Seepage stability is an important factor to ensure the safety of underground mining when mining ore bodies under rivers.To analyze the influence of the Toudaoyangcha river on the seepage stability of underground mining in Sansheng Iron Mine, based on the hydrogeological concept model, the seepage characteristics under the influence of underground mining disturbance in Sansheng Iron Mine were analyzed by using Flac3 D numerical analysis software.The results show that the stoping is less affected by the seepage of the river level, and there is no water inrush risk in the mine.The calculation results can provide a reference for safe mining in mines. [ABSTRACT FROM AUTHOR]

Rock bursts occur in nearly vertical coal seam mines at shallow to moderate burial depths, which endangers safe mining. To study the rock burst mechanisms of nearly vertical and extremely thick coal seams, the characteristics of rock bursts were studied via on-site investigation, and a field test of in situ stress was carried out. The mechanical behavior of rock pillars in the middle of the B1+2 and B3+6 coal seams was analyzed using theoretical and numerical simulation methods. The results show that the horizontal maximum principal stress orientation and the nearly vertical coal seam strike were both 82°. The bending of the rock pillars occurred due to the horizontal unbalanced force, and a large amount of bending energy was accumulated within 50 m above the mining level. Rock pillars were bent toward the B1+2 mining goaf and exerted a reverse bending and squeezing effect on the B3+6 coal seam below the mining levels. In addition to the inclination and compression of the B3+6 coal seam roof, stress concentration zones formed in the B3+6 coal seam, where a large amount of elastic energy had accumulated in the coal-rock mass. Consequently, both the rock pillars and the B3+6 coal body at the mining level are in an unstable state undue to mining disturbance. Rock burst energy theory and numerical calculation results showed that in the stress concentration zones of the B3+6 coal seam, the energy density of the coal mass reached or exceeded its critical value before rock burst occurred, and rock bursts were prone to occur under mining disturbances. The in situ microseismic results showed that high-energy microseismic events were mainly concentrated in middle rock pillars around the mining levels and the coal mass in high-stress concentration zones. [ABSTRACT FROM AUTHOR]

Metal mines mined using the sublevel caving method often exhibit various environmental problems on the ground surface. This can affect the safety of the production process in the mining area. A numerical model using Universal Distinct Element Code has been established to investigate deformation failure giving rise to this underground mining. The calculations are combined with in-situ monitoring data collected over a period of 10 years. The results indicate that the strata movement in the footwall can be divided into two stages: an arch caving development stage and post arch caving development stage. Mining disturbance is the main cause of caving in the arch caving development stage. The overlying strata experience 'caving–stability–caving', leading to the formation of an 'arch-shaped' caving pattern. In the post arch caving development stage, flexural-toppling deformation occurs in the strata in the direction of the collapse pit due to the tectonic stress present and high dip angles of the discontinuities. Through-going failure surface has been analyzed by studying the plastic state and displacement of elements. The formation of through-going failure surface is related to the flexural-toppling deformation and stress concentration caused by mining activities. Based on the different failure mechanisms, an efficient partition has been proposed such that the footwall can be divided into a stable zone, flexural-toppling failure zone, compression and slipping-toppling failure zone, and shear-slipping failure zone. The results are a useful reference when applied to the Chengchao Iron Mine and other similar metal mines. [ABSTRACT FROM AUTHOR]

Taking the soil samples collected at Baorixile Open-pit Mine as the research object, based on the relevant soil hydraulics parameters measured in the laboratory, the groundwater level in the field survey and the relevant meteorological data, the soil water migration law was studied in the aeration zone from 1990 to 2016, the feasibility of using soil water flux to estimate precipitation infiltration coefficient is discussed, and the effects of groundwater level decline and soil reconstruction of dump on precipitation infiltration coefficient are analyzed. The results showed that under the condition of natural rainfall, the average soil water flux at 10 m in the steppe area was 20.38 mm, and the average precipitation infiltration coefficient for many years was 0.06; with the increase of groundwater depth, the precipitation infiltration coefficient firstly decreases and then keeps stable at 2 m, that is to say, the drop of groundwater level in the mining area has little effect on the recharge of groundwater by precipitation; at present, the soil reconstruction model of “humus + clay + medium sand” can greatly improve the moisture content of humus and play a positive role in the vegetation restoration of open-pit dump, but to a certain extent, it reduces the infiltration coefficient of precipitation, which makes it unfavorable for groundwater to accept the recharge of meteoric precipitation.

To study the mining stress evolution law of inclined backfilled stope in deep mining, this paper first proposes a method for determining the parameters of the brittle-ductile transition model corresponding to the Hoek–Brown criterion and Mohr-Coulomb criterion under high geostress. Then, a model composed of inclined backfilled stopes with different depths is established to simulate the sequential mining process of ore bodies with varying depths from shallow to deep. The numerical model's stratum displacement, rock mass stress distribution, and risk factors show that the mining-induced stress will move to the upper stopes and the stratum below the deepest stope. The transfer range and influence degree of mining-induced stress will increase with the increase of the deep mining, resulting in the most dangerous backfilled stope occurring one to two layers above the deepest stope and the apparent stress concentration area occurring below the deepest stope. To prevent disasters caused by mining stress, pillars in inclined deep stopes should have large safety factors. Replacing low-strength backfills with high-strength backfills can reduce the stress concentration in the stratum below the deepest stope. [ABSTRACT FROM AUTHOR]

To address the problem of instability and failure of the 11,514 return air roadway caused by dynamic pressure in Jinhuagong Coal Mine, this study uses theoretical analysis, numerical simulation, and field test methods. The disturbance deformation mechanism and the surrounding rock control technology for the 11,514 return air roadway during face‐to‐face mining and excavation are analyzed. The results show that the causes of regional asymmetric deformation and failure of the surrounding rock of the 11,514 return air roadway are multiple superpositions of lateral bearing pressure of the 11,812 mined‐out area, mining stress in the 8814 working face, and advanced stress of the 11,514 return air roadway. When mining and excavation faces meet, the 11,514 return air roadway is affected by the superimposition of the mining stress. At the same time, the solid coal side of the roadway is in the mining pressure relief area in the 8814 working face in the upper coal seam, and the asymmetric distribution of the principal stress on both sides of the 11,514 return air roadway causes deformation and failure of the surrounding rock. Based on the differences in superimposed stress disturbance in different parts of the roadway, a subsection control technology is proposed. This technology is focused on supporting secondary reinforcement in the range of 40 m before and after the mining overlap position on the 11,514 roadway. Field measurement data confirm the effectiveness of this support technology. [ABSTRACT FROM AUTHOR]

In order to grasp the evolution law of the mechanical characteristics of the floor under the disturbance of the first coal seam mining in Pingmei No.8 coal mine, this paper uses COMSOL Multiphysics software to simulate the stress distribution characteristics of the underlying coal rock layer under the disturbance of Ji15 coal seam mining. Results show that: under the disturbance of first mining layer, the vertical stress field of underlying coal stratum is symmetrically distributed in the middle of working face. Obvious stress-relief zone could be seen above and below the working face of first mining layer. There is stress concentration at both ends of the mining area, and the maximum stress concentration reaches 2.56. The stress-relief effect is within 30 m from the bottom of first mining layer. Meanwhile, the stress releasing rate could reach more than 95%, and the length of sufficient stress-relief zone could reach 70.22% of the length of working face in first mining layer. Therefore, the coal seam within 30 m of stress-relief layer should be preferentially selected as the first mining layer.

Taking 1604 working face of Guhanshan Mine as the research background, by means of a high-precision micro-seismic monitoring system and numerical simulation, the dynamic failure characteristics of the surrounding rock and the danger of water inrush from the floor during the mining of the working face are studied. The results show that the asymmetrical energy release phenomenon occurs along the empty side and along the solid coal side of the bottom floor rock mass along the two sides of the working face. Among them, the bottom floor rock mass along the solid coal side has the largest damage scale with a depth of about 30 m. At a position of 12 m under the floor and 8 m in the inner staggered transportation lane, the energy density value of the surrounding rock is between 5-50 J/m2. Combined with the monitoring results of the surrounding rock deformation of the roadway, it is considered that the bottom pumping lane is located at this position and the mining disturbance is lower; the pumping roadway is located directly below the transport roadway or outside the transport roadway. The energy density of the surrounding rock release is greater than 100 J/m2, and the degree of disturbance is high. The numerical simulation results show that the bottom slot is located in the pressure relief area of the floor when the staggered groove is 8 m, which is located directly below the groove and is in the stress concentration area when the staggered groove is outside.

The rock burst induced by the mutual disturbance of mining and excavation is significantly influenced by high static load stress and external dynamic load disturbance. In this paper, the evolution characteristics and progressive damage mechanism of surrounding rock in the process of mutual disturbance of mining and excavation are systematically studied. The results show that the evolution of surrounding rock stress can be roughly divided into three stages: rapid rise in the early stage, continuous rise and step-like decline in the middle stage, and slow rise in the late stage. In the process of parallel mining, the overlying rock movement above the goaf shows the sequence of horizontal penetration of tiny fissures—fracture intensification transition to stratification—non-coordinated caving of middle–low overlying rock—obvious horizontal cracks in the upper key layer. Only under the quasi-static loading mining action does the upper key layer not reach the breaking condition. The wave side of the heading face which is close to the focal point is affected by the dynamic load disturbance, the acceleration duration is short, and the attenuation is relatively fast, so it is the area prone to the earliest impact failure in the face of mining disturbance. The conclusion is helpful to deepen the understanding of the coal burst mechanism of mutual disturbance of mining and excavation.

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Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Special mining methods and red soil lead to large-scale land degradation and desertification in ion-type rare earth (RE) mining areas. Therefore, it is crucial for ecological management and restoration of mining areas to accurately understand the evolution process of desertification. In this study, remote sensing Landsat images from 1986 to 2019 were used to extract desertified land information from the Lingbei mining areas, Dingnan County, Ganzhou, China. To improve the reliability of the experiment, samples selected from Google images were used for verification to compare the accuracy of the desertification difference index (DDI) model and random forest (RF) algorithm for extracting land desertification information. The results showed that compared with the DDI model, the overall accuracy and kappa coefficient of the RF model based on multiple features were improved by 7% and 9.37%, respectively, indicating its higher applicability. Spatiotemporal change analysis of desertification in the mining area showed that the total area of desertification in the mining area increased most rapidly during 1986–1994 and reached 60.75 km2. The area of desertified land increased continuously from 1994 to 2004 and reached a maximum of 143.08 km2 in 2004. The area of desertified land decreased by 50.27 km2, but the severe desertified land (SDL) area increased by 1.69 km2 during 2004–2011. The area of desertified land gradually declined and stabilized from 2011 to 2019. Analysis of the desertification process in mining areas under different disturbance conditions showed that the desertified land disturbed by RE mining was most severely damaged. There is still an area of 16.77 km2 in the process of restoration, of which 2.24 km2 belongs to the SDL level. Moderate desertified land (MDL) and light desertified land (LDL) have not been completely contained and require the attention of the relevant departments to ensure their timely reclamation. [ABSTRACT FROM AUTHOR]

To discuss the hydrochemical evolution characteristics of the mining process of Peigou Coal Mine, based on the test results of 43 water samples collected at different times from three main discharge aquifers, namely, Carboniferous Taiyuan Formation limestone water (L7–8 + L5–6 water), Ordovician limestone water (including Taiyuan Formation L1–4), and Permian main mining coal seam roof and floor sandstone water (roof and floor water), a hydrochemical evolution model of the mining disturbances since 2003 has been established. The carbonate and sulphate dissolution and pyrite oxidation in Ordovician limestone water significantly decreased and then increased in 2006, and silicate weathering was weak. The carbonate and sulphate dissolution, silicate weathering and pyrite oxidation of roof and floor sandstone water increased. At the same time, a water source identification model suitable for the Peigou Coal Mine was developed by comparing the Fisher discriminant and the BP (back propagation) neural network discriminant. The accuracy rates of Fisher discriminant and BP neural network discriminant are 81.40% and 83.72% respectively, which indicates that BP neural network is more accurate. Finally, the evolution of hydraulic connection between aquifers is analysed. We speculate that there is a fracture development channel between Ordovician limestone water and roof and floor water aquifers that is affected in 2005 by the mining disturbance. This study has significance for examining the hydrochemical evolution of groundwater in mines and acting as a guideline to prevent and control water inrushes. [ABSTRACT FROM AUTHOR]

The mining activities of ion⁃type rare earth have caused extremely ecological disturbances on the surface of the mining area and caused local ecological and environmental problems. The variation of surface thermal environment in the mining area can better reflect the ecological disturbance characteristics of the mining area, and is an important parameter to identify surface ecological disturbances. The ion⁃type rare earth area has the characteristics of scattered ore and small single⁃site area, thus obtaining the surface temperature data with strong practicability and higher spatial resolution is valuable to the monitoring of the eco⁃ logical environment of the rare earth mining area. We constructed a temperature downscale model with image fusion and spectral unmixing. The Lingbei ion⁃type rare earth district in Dingnan County of Ganzhou City is selected as the study area. The Landsat 8 satellite image is used as main data source. Firstly, we select data of two seasons in the same year,and combine the integrated image fusion algorithm and linear spectral mixture model . The surface temperature resolution of the surface is downscaled to 15m. Then, the land surface temperature results after downscaling are qualitatively and quantitatively analyzed and tested for accuracy. The results show that the spatial distribution of the surface temperature and the overall trend of the mining area before and after the decomposition are consistent. The surface temperature after the down⁃scaling can reflect the surface features and spatial differences of the mining area in more details. The overall root mean square error （RMSE） of the two seasonal phases in the study area are respectively for 1.459 K and 1.196 K, the mean absolute error （MAE） are 1.128 K and 0.952 K respectively with high accuracy. Our proposed method has high applicability for improving the spatial resolution of the surface temperature of the ionic rare earth. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A physical model experiment was conducted to study the surrounding rock failure mechanism for the roadway under deviatoric pressure from mining disturbance. During the excavation process, a self-developed deviatoric pressure reaction system was used to realize deviatoric pressure loading. Meanwhile, a digital photogrammetric measurement system and a static strain data collection system were utilized to obtain the deformation, strain and stress of the model. The deviatoric pressure stress field characteristic and deformation failure mechanism of roadway were investigated by synthetic analysis of experimental data and displacement vector diagram. The physical experimental results showed that mining disturbance had an inevitable influence on the formation of roadway deviatoric pressure, which caused the V-shaped distribution of pressure stress above the roadway. The V-shaped deviatoric pressure stress caused the roadway asymmetric deformation that was proportional to the deviatoric pressure stress above the roadway. And the asymmetric deformation further aggravated the degree of deviatoric pressure stress and formed a vicious cycle, which resulted in the instability of the roadway. In addition, a numerical simulation under deviatoric pressure was conducted to verify the accuracy of physical experimental results. This study can provide helpful references for researching the instability behavior of the roadway. [ABSTRACT FROM AUTHOR]

Water inrush disasters from the coal seam floor occur frequently due to the high water pressure of the Ordovician limestone aquifer, multiple aquifers and strong mining disturbance. We presented a model of water-resisting key strata (WRKS) to investigate the mechanism of floor water inrush from multiple aquifers in deep coal mines. Roof hydraulic fracturing (RHF) for controlling floor water inrush and multi-parameter monitoring were proposed and validated in the Xingdong coal mine in Xingtai, Hebei Province. The results indicated that the periodic weighting step of the test working face after RHF was 9.53 m, which was 61.42% less than that of the working face without RHF (24.7 m). The floor failure depth was 30 m, which was 34.4% less than that of the zones without RHF (45.7 m). Hydraulic fracturing weakened the strength of the overlying strata to control the weighting step and reduce the mining disturbance stress, and the stability of the floor WRKS was enhanced, thereby preventing water inrush from the coal seam floor. The research results provide a solution for preventing floor damage and floor water inrush under strong mining disturbance and in complex hydrogeological environments in deep mining.

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Throughout the Central Appalachian ecoregion, mountaintop removal coal mining (MTM) is the predominant form of land use change. The streams draining MTM impacted watersheds have been reported to contain high stream nitrate (NO3−) concentrations, yet the source and persistence of elevated NO3− remains unknown. Here we compiled data from multiple sources to conduct a regional evaluation of the impact of mining on stream NO3−, examine NO3− persistence after mining cessation, and identify potential N sources. Using water quality data from six large watersheds, we observe elevated NO3− in watersheds with the highest active mining density. At four small MTM watersheds with repeat sampling, we found that high levels of NO3− concentrations declined after mining cessation but remain elevated above reference after several decades. At MTM watersheds, we found annual mass flux of NO3− was 3.68 to 26.4 kg N ha−1 year−1, which is 1 to 2 orders of magnitude higher than a nearby forested reference watershed. Stream water NO3− isotopic ratios at these sites did not match previously suggested NO3− sources such as explosives used during mining and fertilizer applied during reclamation but were highly enriched in both δ15N and δ18O compared to the reference watershed suggesting high rates of NO3− retention. Explosive residue could account for the bulk of watershed NO3− export during active mining phases but other mining related N sources including fertilizer and rock‐derived N, the construction of valley fills, and alterations in watershed NO3‐ cycling likely contribute to the persistence of elevated NO3− export observed in this study. Plain Language Summary: Mountaintop removal coal mining, a form of surface coal mining common in Central Appalachia, causes deep transformations of previously forested mountain landscapes. Previous studies demonstrated that mining adversely impacts downstream water quality including causing high levels of dissolved nitrate, a form of nitrogen. Excessive stream water nitrate can damage stream food webs, trigger algal blooms, and pose a threat to human health. This work identifies elevated nitrate as a widespread problem caused by mountaintop removal coal mining. We sought to identify the sources of this nitrate and how long the problem persists after mining stops. We found evidence that nitrate levels in Central Appalachian rivers increased with the amount of active mining in their watersheds. In heavily mined watersheds, we found the level of nitrate exported was 1 to 2 orders of magnitude higher than at an adjacent forested watershed. Nitrate levels remained higher in mined watersheds even several decades after mining ended. Our work identifies explosives as a likely source of stream water nitrate during active mining. In addition, changes to the physical structure of the landscape and the increased chemical breakdown of newly exposed rock may also contribute to persistent high nitrate levels in affected streams. Key Points: Nitrate fluxes from mined watersheds were 1‐2 orders of magnitude higher than an adjacent forested watershed, impacting regional water qualityNitrate export declined after the cessation of active mining but persisted above reference levels for decades post‐miningThe persistence of mining‐associated N export suggests N sources are linked to deeper flow paths within constructed valley fills [ABSTRACT FROM AUTHOR]

To explore the differences in deformation failure and energy evolution and simulate the real excavation conditions of coal masses at different depths during the coal-mining process, an unloading failure experiment was conducted. The experiment included coal samples at different depths from the no. 15 coal seam of the Ji group in the Pingmei coal-mining area. The sample depths were 300, 600, 700, 850, and 1050 m. The in situ stress environment, physical rock properties, and excavation disturbance influence were considered in the analysis. The results show that as the depth increases, the peak strength and residual strength of coal samples increase nonlinearly and that the deformation capacity simultaneously increases. The elastic strain energy stored before the unloading of coal, the total energy input, the accumulated elastic energy, and the dissipated energy generated during failure all increase with increasing depth, and the ratios of these results for the 1050–300 m samples were 10.79, 3.75, 3.78, and 4.67, respectively. A prepeak stage energy evolution model was established for coal samples from different depths, and the energy transformation trends of the deformation and failure of coal were explored from the perspective of the energy evolution rate. The energy dissipation efficiency (ued) was defined to represent the energy dissipation generated per unit of energy input. When the energy input is mainly transformed to dissipation energy, the failure of coal occurs (ued > 0.5), and the energy is predominantly associated with crack growth at this point, so the coal is quickly destroyed. This conversion occurs earlier as the depth increases. The AE energy release trend exhibited a good correspondence with the increases in the energy dissipation, dissipation rate, and dissipation efficiency with depth during coal unloading failure, which indicates a more intense failure of the coal body at deeper depths. [ABSTRACT FROM AUTHOR]