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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]

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 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]

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.

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]

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]

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]

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.

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]

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.

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]

Understanding the permeability characteristics of coal under mining disturbance is crucial for ensuring coal mine safety and efficient gas extraction. Coal is a dual porosity medium consisting of matrix and fracture, and there are some differences in mechanics and permeability between matrix pores and fracture. However, research on the damage and gas seepage characteristics of dual-porosity coal is limited. In this paper, a coupled damage-permeability model considering matrix pores and fractures in coal is established, incorporating the influences of effective stress, gas adsorption, thermal expansion, and thermal cracking. And the reliability of the newly developed model was verified using experimental data of temperature and pressure variations under different stress boundary conditions. The results indicate that during the elastic stage, the total permeability and fracture permeability of coal exhibit a trend of decreasing and then increasing with pore pressure, while matrix permeability gradually increases. In the full stress-strain stage, the overall damage-permeability and fracture damage-permeability of coal exhibit an "S"-shaped variation trend with axial strain, while matrix damage-permeability shows a slow increasing trend. To accurately characterize the evolution of gas seepage in coal, contributions from matrix pores and fractures must be comprehensively considered, and the effects of gas adsorption, effective stress, thermal cracking, and thermal expansion on permeability cannot be ignored. Furthermore, through parameter sensitivity analysis, it is found that during the elastic stage, coal permeability decreases with an increase in the adsorption sensitivity coefficient and thermal expansion coefficient. In the full stress-strain process, coal permeability increases with an increase in the damage-permeability coefficient. The results of this study are of great significance for predicting the evolution of coal permeability in the working face ahead under mining disturbance. • The crack unit surface energy was introduced as a random distribution variable to characterize the crack-induced damage. • A damage-permeability model of dual-porosity coal under thermal-mechanical coupling was constructed. • The variation laws of permeability and damage variables in different structures were explored. • The effects of effective stress, gas adsorption, and temperature on dual-porosity permeability of coal were discussed. [ABSTRACT FROM AUTHOR]

The depth effect of coal mechanical behavior seriously affects the safety and efficiency of deep coal mining. To explore the differences in failure behavior and damage characteristics of coal masses at different depths during the coal mining process, based on the consideration of in situ stress environment, physical properties, and mining disturbance of coal seams, triaxial unloading experiments with acoustic emission (AE) monitoring were conducted on coal samples at four different depths taken from the Pingdingshan coal mine area. The results showed that the AE activity of deep coal was more concentrated, and the cumulative AE energy of coal increased with increasing depth. The cumulative AE energy of the 1050-m coal sample was 69 times that of the 300-m coal sample. The b value representing the microcrack scale decreased with increasing depth, and the rupture degree of deep coal increased. The cracking mode of coal was classified and the failure behavior was analyzed. The cumulative tensile crack percentage of coal increased with increasing depth, and the tensile–shear composite failure occurred in the 300-m coal sample, whereas significant tensile failure occurred in the 1050-m coal sample. In addition, the damage evolution process of coal was divided into three stages, and the characteristic stress of coal was obtained. The ratio of crack initiation stress (σci) to peak stress (σc) increased with increasing depth, and the damage evolution process of deep coal was more rapid. The research results can provide useful guidance for disaster prevention and evaluation of surrounding rock stability during deep coal resource mining in the Pingdingshan coal mine area.

Some of the coal deposits in the northwest region of China are at relatively shallow depths, covered by a thin layer of bedrock and a thick layer of wind-blown sand. We studied the mechanics and permeability of a clay aquiclude by X-ray diffraction and triaxial loading tests and the fracturing of the overlying bedrock and aquiclude in physical simulation tests. The results indicate that if the bedrock thickness is 90 m or more, the height, distribution pattern, and damage to the water-conducting fractured and caving zones ("belts") are normal. If the bedrock thickness is 30 m or less, the "three belts make one" phenomenon occurs, and caving extends into the soil layer; the overlying rock is completely perforated by vertical fractures and the collapse spreads to the surface. When the bedrock thickness is between 30 and 90 m, the height of the water-conducting fractured zone is inhibited by the weathered rock and cohesive soil layers, and the height of the "two belts" is significantly decreased. This can be used to prevent and control coal mine water hazard. [ABSTRACT FROM AUTHOR]

Open‐cut mining severely disrupts landforms and soils, preventing or impeding the restoration of preexisting or functional ecosystems because essential properties of the original soils cannot immediately or easily be reinstated. We examined the soil physicochemical and bacterial characteristics of 21 coal‐mined sites in subtropical Queensland, Australia, 3–23 years after establishment of native plant species relative to nonmined analogue sites. Soil disturbance significantly decreased total nitrogen, nitrate nitrogen, and especially total carbon (TC). The TC is projected to take 36 years to recover. Bacterial communities assessed by 16S ribosomal RNA sequencing showed greater species richness and evenness in rehabilitated as compared with nonmined soils, regardless of rehabilitation age. However, bacterial species composition was associated significantly with soil electrical conductivity, the plant density, and total stem cross‐sectional area of woody vegetation. The bacterial communities on rehabilitated sites became progressively more similar to those of nonmined analogue sites over time. This work demonstrates that if topsoils are conserved carefully during mining and supplemented by inorganic fertilizer addition, vigorous plant growth and changes in bacterial community composition can occur soon after plant establishment. This will mitigate the effects of soil disturbance and accelerate the return to the chemical and biological attributes of nonmined analogue soils. [ABSTRACT FROM AUTHOR]

To improve the recovery ratio of coal resources and stress environment of the roadway, gob-side entries have been widely implemented to numerous coal mines in China. Traditional gob-side entry is generally excavated after the gob of the adjacent longwall face is stabilized. To achieve a balance between the seam mining and roadway excavation, numerous mine coals use the method of driving a roadway along the next gob, which heads adjacent to the advancing coal face, and maintaining a narrow coal pillar. Consequently, the dynamic pressure occurs at the gob-side entry; accordingly, the difficulty of roadway maintenance is increased. However, the traditional gob-side entry stability analysis is not applicable to a gob-side entry under dynamic pressure. In this study, the overburden structural model and coal pillar stress model of a gob-side entry under dynamic pressure were established considering the compression load of the immediate roof and gangue and influence law of the cantilever beam length of main roof. Subsequently, thickness, hardness, and deformation of the immediate roof on the stability of the gob-side entry were studied, and the theoretical criterion for the stability of "voussoir beam" structure and coal pillar of the gob-side entry under dynamic pressure were proposed. Based on the geological conditions in tailgate # 110505 of the Yushuling coal mine, reasonable measures were taken considering the aspects of roof cutting and pressure relief, coal pillar design, and surrounding rock reinforcement. After applying the proposed measures, the width of the coal pillar was reduced from 15 m to 4 m. Meanwhile, the grouting cable beam was used to strengthen the roof, and the narrow coal pillar was reinforced by a bidirectional grouting anchor cable was developed. As a result, after the roadway was stabilized, the roof-to-floor convergence and two-side convergence were 268 mm and 105 mm, respectively. Moreover, the stress concentration factor of the coal pillar was 1.20. The stability characteristics of the overburden and coal pillar of the gob-side entry under dynamic pressure were effectively controlled, and remarkable economic benefits were obtained in this coal mine. The techniques proposed for maintaining the stability of the 4 m wide coal pillar and ensuring the bidirectional grouting reinforcement have been successfully applied in a coal mine for the first time, which have high innovation and application values. This study provides a reference for the design and maintenance of the gob-side entry under dynamic pressure. [ABSTRACT FROM AUTHOR]

• A FLAC3D zonal osmotic unsaturated seepage model including water immersion weakening effect based on water-resisting coal pillar was established, and the influence of water seepage distribution on the stability of water-resisting coal pillar under mining and water immersion superposition was studied. • It is proposed that the lateral boundary intersection of the water-conducting fissures on both sides of the overlying strata and the connection between the seepage zone on the waterlogged side and the plastic zone on the mining side inside the water-resisting coal pillar as the critical conditions for the failure of both. • A reasonable retention width determination method based on the distribution of the internal water seepage, the central elastic compression tight water barrier, and the plastic zone of the water-resisting coal pillar were proposed. • Based on the deficiencies of finite element numerical simulation calculations in simulating fractured rock formations, a Fish language based on the stiffness weakening effect of overlying strata was developed. • It is proposed to consider the influence of the water barrier capacity of the overlying strata when the coal pillar with different widths is retained, that is, the stability of the "coal pillar-overburden" synergy water barrier capacity on the safe mining of the working face. The construction of coal mine underground reservoirs utilizing old goaf as storage space plays an important role in the ecological environment and economic development of arid mining areas. The destruction and design of coal pillars have always been the focus of research on the stability of coal mine underground reservoirs. Under the combined effect of mining and water immersion, the water-resisting coal pillar is easy to cause gradual damage and instability. Based on this, a numerical simulation method of fluid–solid coupling considering the zoned osmotic unsaturated seepage characteristics and the water immersion weakening effect of water-resisting coal pillars, and the collaborative water-blocking mechanism of coal pillars and overlying strata were proposed to quantify the stability of coal mine underground reservoirs. In the simulation process, the coupled distribution characteristics of the seepage field, plastic zone, and stress field of the permeable flow of coal pillars with different widths under mining and water immersion were realized, and the water-blocking mechanism of the overlying strata based on the distribution characteristics of the water-conducting fissure lateral boundary was studied. Meanwhile, it is proposed that the lateral boundary intersection of the water-conducting fissures on both sides of the overlying strata and the connection between the seepage zone on the waterlogged side and the plastic zone on the mining side inside the water-resisting coal pillar as the critical conditions for the failure of both. Therefore, a reasonable design method for the width of the water-resisting coal pillar was proposed to prevent failure, which includes "water seepage zone + elastic pressure-dense water-resistance zone + plastic zone" three-zone distribution and considers the distribution characteristics of the overlying strata, which are "water-conducting fissure zone + middle extrusion water-blocking zone". The reasonable width was determined to be 150 m for the water-resisting coal pillar, and on this basis, the dynamic degradation mechanism of the load-bearing capacity of the 150 m coal pillar under multi-field coupling during the entire mining process was quantitatively analyzed. Therefore, an engineering method was proposed to support and reinforce the water-resisting coal pillar and reasonably drain the water in the upper segment. This study is expected to provide theoretical guidance for the stability research and reasonable width determination of the water-resisting coal pillar in the protection of water resources in the water-rich goaf and the safe mining of adjacent working faces. [ABSTRACT FROM AUTHOR]

Results of mycological research conducted in the years 2001–2013 in the restoration stands growing on reclaimed mine spoils are presented. Four opencast lignite mine spoil heaps in Poland were examined: Pątnów-Jóźwin, Adamów, Mt Kamieńsk, and Turów. The paper focuses on 71 species of ectomycorrhizal fungi: recorded for the first time in the country (16 taxa), currently red-listed (23 taxa), known from few localities only (32 taxa). Notes on their ecology and habitats are provided, as well as their distribution in Europe and in Poland. Restoration tree stands, established as part of the reclamation process of mine spoils, form a unique habitat for many rare and interesting fungal taxa. Among them are pioneer species, species known mainly from Northern Europe or mountainous locations, highly specialized and narrow-niche taxa, and many threatened species. Afforested mine spoils contribute significantly to the fungal biodiversity, both at a local and at a larger scale.

Results of mycological research conducted in the years 2001–2013 in the restoration stands growing on reclaimed mine spoils are presented. Four opencast lignite mine spoil heaps in Poland were examined: Pątnów-Jóźwin, Adamów, Mt Kamieńsk, and Turów. The paper focuses on 71 species of ectomycorrhizal fungi: recorded for the first time in the country (16 taxa), currently red-listed (23 taxa), known from few localities only (32 taxa). Notes on their ecology and habitats are provided, as well as their distribution in Europe and in Poland. Restoration tree stands, established as part of the reclamation process of mine spoils, form a unique habitat for many rare and interesting fungal taxa. Among them are pioneer species, species known mainly from Northern Europe or mountainous locations, highly specialized and narrow-niche taxa, and many threatened species. Afforested mine spoils contribute significantly to the fungal biodiversity, both at a local and at a larger scale. [ABSTRACT FROM AUTHOR]

Elucidating the responses and potential functions of soil microbial communities during succession is important for understanding biogeochemical processes and the sustainable development of plant communities after environmental disturbances. However, studies of such dynamics during post-mining ecological restoration in alpine areas remain poorly understood. Microbial diversity, nitrogen, and phosphorus cycle functional gene potential in the Heishan mining area of Northwest China was studied, including primitive succession, secondary succession, and artificial succession disturbed by mining. The results revealed that: (1) The dominant bacteria in both categories (non-remediated and ecologically restored) of mining area rhizosphere soil were Proteobacteria , adopting the r strategy, whereas in naturally occurring soil outside the mining area, the dominant bacteria were actinomycetes and Acidobacteria , adopting the k strategy. Notably, mining perturbation significantly reduced the relative abundance of archaea. (2) After restoration, more bacterial network node connections were observed in mining areas than were originally present, whereas the archaeal network showed the opposite trend. (3) The networks of microbial genes related to nitrogen and phosphorus cycle potential differed significantly, depending on the succession type. Namely, prior to restoration, there were more phosphorus related functional gene network connections; these were also more strongly correlated, and the network was more aggregated. (4) Soil factors such as pH and NO 3 –N affected both the mining area remediation soil and the soil outside the mining area, but did not affect the soil of the original vegetation in the mining area. The changes in the structure and function of plant rhizosphere microorganisms after mining disturbance can provide a theoretical basis for the natural restoration of mining areas. • Mining disturbances are associated with a change in soil nutrients. • Proteobacteria r-strategists dominated secondary artificial successions post-mining. • Actinobacteria and Acidobacteria k-strategists dominated original succession soil. • Mining perturbation significantly reduced the relative abundance of archaea. • N and P cycling network in the metagenome useful to explore soil microorganisms. [ABSTRACT FROM AUTHOR]

Coal mining under a body of water introduces a potential risk of water inrush to the mine. Based on the practice of coal mining near the Jinsha river in Gansu province, China, and focused on the seepage prevention of the mining-disturbed riverbed, the surface movement, failure characteristics of the overburden strata, and water percolation induced by mining underneath the river have been investigated by means of in situ monitoring, physical modeling, and discrete element numerical simulation. A flexible anti-seepage scheme, Four Element Structure (FES), is put forward to protect the riverbed from seepage, and the structure can harmonize and buffer the mining-induced deformation of the surface land. Upward from the bottom of the riverbed, FES is composed respectively of: Reinforcement layer , which plays the roles of strengthening the riverbed, buffering the deformation, and enhancing the integrity of the riverbed; Bedding course layer , which prevents the anti-seepage layer from folding damage due to dislocation and sharpness in the riverbed, meanwhile it can absorb localized deformation; Anti-seepage layer , which is a major anti-seepage texture made by geo-membrane with the properties of water proof, a high strength, good flexibility and ductility; Protective layer , which covers the geo-membrane by a layer of precast reinforced concrete bricks to fix and protect the anti-seepage layer. In addition, treatment principles are proposed for reshipping of the river path in plane, the stream gradient along the longitude and the shape of cross section of the riverbed, and a comprehensive seepage prevention system is established. [ABSTRACT FROM AUTHOR]

The environmental changes caused by coal mining activities caused disturbances to the plant, soil, and microbial health in the mining area. Arbuscular mycorrhizal fungi (AMF) play an important role in the ecological restoration of mining areas. However, it is less understood how soil fungal communities with multiple functional groups respond to coal mining, and the quantitative impact and risk of mining disturbance. Therefore, in this study, the effect of coal mining on soil microorganisms' composition and diversity were analyzed near the edge of an opencast coal-mine dump in the Shengli mining area, Xilingol League, Inner Mongolia. The response strategy of soil fungi to coal mining and the stability of arbuscular mycorrhizal fungi (AMF) in the soil fungal community were determined. Our results showed that coal mining affected AMF and soil fungi in areas within 900 m from the coal mine. The abundance of endophytes increased with the distance between sampling sites and the mine dump, whereas the abundance of saprotroph decreased with the distance between sampling sites and the mine dump. Saprotroph was the dominant functional flora near the mining area. The nodes percentage of Septoglomus and Claroideoglomus and AMF phylogenetic diversity near the mining area were highest. AMF responded to the mining disturbance via the variety and evolution strategy of flora. Furthermore, AMF and soil fungal communities were significantly correlated with edaphic properties and parameters. Soil available phosphorus (AP) was the main influencer of soil AMF and fungal communities. These findings evaluated the risk range of coal mining on AMF and soil fungal communities and elucidated the microbial response strategy to mining disturbance.

In engineering activities involving the mining of coal resources, gas is the main factor for causing coal and gas explosions accidents, with permeability being an important parameter in estimating gas emissions. With the steady development of the mining face, stress in front of the work face has evidently changed, that has resulted in coal damage under mining disturbance. In the underground environment, coal is in a complex environment where water, gas and external loads combine with each other, leading to changes in permeability that are often extremely complex, with effective stress being the dominant factor to changes in permeability. Therefore, coal permeability change related to damage-induced effects under different water contents should be further studied. In this study, first, the influence of water, gas adsorption and effective stress on coal fracture permeability change were considered. Further, damage variables were introduced to combine mechanical damage with water weakening damage. By quantifying changes in matrix sizes with new fracture generations, the plastic deformation in fractures was estimated. Based on a cubic model, a damaged-induced permeability model under the interaction of hydro-mechanical effects was established. From this, a triaxial seepage experiment involving the whole stress-strain process, including effective stress changes of water-bearing coal, was conducted to compare with, and to verify the results against an established model. The experimental results revealed that changes in axial strain and permeability was "S" shaped during the whole stress-strain process. In addition, during the whole stress-strain and effective stress changes process, the permeability model corresponded well with the experimental results. This demonstrated that the model could not only predict permeability change under elastic deformation, but could also describe permeability changes under plastic deformation during the damage stage. The purpose of this study was to provide a new method for predicting the permeability evolution law relating to coal mining and gas extraction. • Seepage experiments on effective stress changes and whole stress-strain process of water-bearing coal were conducted. • The influence of water, sorptive gas and effective stress combined damage mechanics on the fracture strain of coal is considered. • Based on cubic model, a permeability model was established considering the elastic-plastic deformation in different stages. [ABSTRACT FROM AUTHOR]