Green Mining

To promote the sustainable exploitation of open-pit coal resources, waste is used as backfill material to realize the comprehensive utilization of solid waste mine resources. We proposed a mining method that is a combination of the highwall mining and filling mining methods. Cemented paste backfill (CPB) samples were prepared with high-clay-mineral-content marl particles as aggregate and normal Portland cement, sulfoaluminate cement and gypsum as cementing materials. The physical and mechanical properties and microstructural evolution of CPB with different binder ratios under wetting–drying cycles were measured. The results showed that the CPB with 0–3 wetting–drying cycles underwent shear and tensile coalescence, and that with 4–10 cycles underwent shear coalescence. The unconfined compressive strength (UCS) and elastic modulus (EM) decreased exponentially with increasing number of wetting–drying cycles but decreased exponentially and cubically with increasing porosity, respectively. The EM is more sensitive to gypsum content than the UCS. CPB deterioration was divided into an initial deterioration stage and a secondary deterioration stage. The evolution curve of the total damage variable presents an ‘S’ shape, with an initial damage stage, an accelerated damage expansion stage, a decelerated damage expansion stage and an end damage stage. The research results provide a basis for improving the recovery rate of resources under highwall conditions, and the extensive utilization of stripping materials, and promote the coordinated development of coal resource exploitation and environmental protection. Full article

To maintain high-level economic development, protect the ecological environment, and achieve carbon peaking and carbon neutrality goals, the construction of green mines has become a critical issue in China. In this study, the importance of mineral resources to human society is discussed, and the construction experiences and sustainable development directions of green mines are summarized, which can provide valuable references for the global mining industry. The entry and management process in China was introduced to help understand green mines’ construction objectives and tasks. Moreover, based on the successful construction cases of green mines, four typical green mine models are concluded: the green technology mining model, operation modernization mining model, stability mining model, and ecological restoration mining model. In addition, the key construction elements of green mines are concluded, for example, the mining environment, mining methods, comprehensive utilization of resources, energy conservation, emission reduction, scientific and technological innovation and intelligence, and enterprise-land stability, which provided the directions and guidance for green mine construction. Full article

Three-dimensional resistivity/chargeability tomography based on distributed data acquisition technology is likely to provide abundant information for mineral exploration. To realize true 3D tomography, establishing transmitter sources with different injection directions and collecting vector signals at receiver points is necessary. We implemented 3D resistivity/ chargeability tomography to search for new ore bodies in the deep and peripheral areas of Huaniushan, China. A distributed data acquisition system was used to form a vector receiver array in the survey area. First, by using the expanding gradient array composed of 11 pairs of transmitter electrodes, we quickly obtained the 3D distributions of the resistivity and chargeability of the whole area. Based on the electrical structure and geological setting, a NE-striking potential area for mineral exploration was determined. Next, a pole–dipole array was employed to depict the locations and shapes of the potential ore bodies in detail. The results showed that the inversion data for the two arrays corresponded well with the known geological setting and that the ore veins controlled by boreholes were located in the low-resistivity and high-chargeability zone. These results provided data for future mineral evaluation. Further research showed that true 3D tomography has obvious advantages over quasi-3D tomography. The expanding gradient array, characterized by a good signal strength and field efficiency, was suitable for the target determination in the early exploration stage. The pole–dipole array with high spatial resolution can be used for detailed investigations. Choosing a reasonable data acquisition scheme is helpful to improve the spatial resolution and economic efficiency. Full article

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. Full article

Significant interest has been focused on recovery rates, recovery options, and recovery utilization when tailings impoundments are re-mined. However, the stability of the tailings dams during the recovery process is also a severe issue. Based on engineering geological surveys and laboratory tests, the evolution of the Tongling tailings impoundment’s instability characteristics under different recovery heights and diverse working conditions was analyzed by numerical simulation. Firstly, with the help of 2D software, the position of the tailings dam infiltration line and the alteration of the dam safety factor during the stoping process were calculated. Secondly, 3Dmine (2017) software was used to create the 3D surface structure of the tailings impoundment, and then a 3D numerical analysis model was established by means of Midas GTS NX software. The numerical simulation of seepage and stress analyses were conducted based on the model. Consequently, the evolution of the stability characteristics of tailings dam under different operating conditions was calculated. The research demonstrates that the dry beach length of the tailings pond gradually reduces with a decrease in the extraction height, resulting in a lower infiltration line. Under flood conditions, the saturation line has partial overflow due to the poor seepage discharge capacity of the dam. The total displacement of the dam body is inversely proportional to the retrieval height. The more extreme the analyzed working conditions, the more the safety factor will be reduced. Additionally, the plastic variation area of the dam body will be more comprehensive, which will increase the risk of a dam collapse. Full article

Aeromagnetic measurement plays an important role in mineral exploration, but unmanned aerial vehicles generate maneuvering noise during aerial flight, which negatively impacts the accuracy of aeromagnetic measurement data. Therefore, aeromagnetic compensation is an indispensable step in aeromagnetic data processing. The multicollinearity of variables in the aeromagnetic compensation model based on linear regression affects its accuracy, resulting in a large difference in the compensation effect of the same group of compensation coefficients in different directions. In order to obtain high-quality aeromagnetic data, this study proposes an adaptive model-based method for suppressing aeromagnetic maneuvering noise. First, due to the fact that the variables that cause multiple collinearity in the compensation model are related to the flight heading, the model variables are adaptively assigned to each heading based on the characteristics of the variable data for different headings. The compensation model is optimized and improved, and the impact of multiple collinearity is thus suppressed. In adaptive modeling, variables with greater significance and smaller multicollinearity are automatically allocated to build the optimal heading model, and then high-precision compensation coefficients are obtained. This algorithm was applied to the data collected by a certain unmanned aerial vehicle aeromagnetic measurement platform in Ma’anshan and compared with traditional methods. The experimental results show that the adaptive modeling-based aeromagnetic compensation algorithm is superior to traditional algorithms, with fewer errors and a higher improvement ratio. Hence, the method can effectively solve the ill-conditioned problem of a model affected by multicollinearity and further improve its compensation accuracy and robustness. Moreover, the feasibility and value of this algorithm were verified in actual mineral resource detection. Full article

Artisanal gold mining (AGM) is a very important topic, of which the environmental and social impact has been widely studied. However, there are few studies on operational efficiency, financial analysis, and the lack of mine planning. The purpose of this work was to investigate whether AGM operation without mercury is sustainable. The following parameters were analyzed in the case study: the general situation, interaction with the company that owns the area, production, drilling and blasting, loading and transport, freight to the centralized plant, workforce, materials and supplies, geological control planning and the relationship with the processing plant. Even without the mercury variable, AGM was found to be unsustainable. The lack of planning and operational inefficiency did not allow for continuous operation. The results of this research provide guidance on the future steps the current government and society should take to achieve sustainable AGM. Full article

The mining of mineral resources has caused serious damage to land and significant pressure on ecological environment. During the repairing of damaged land and degraded ecosystems, there have been many pieces of literature related to land reclamation and ecological restoration (LRER) that have emerged. To understand the progress and prospect of LRER research, it is necessary to sort out such pieces of literature, analyze the current research status, and forecast the future research directions. Here, Bibliometrix R-package was used to analyze 2357 articles, which were derived from the core database of Web of Science, to explore the development of LRER from 1990 to 2022. The results are as follows. (1) The annual scientific output results show that both the number of articles published on LRER and the number of articles annually citied were increasing gradually from 1990 to 2022. (2) High-frequency keyword analysis indicates that heavy metal (Cd, Pb) pollution remediation is a research hotspot. The cluster analysis (CA) and multiple correspondence analysis (MCA) show that there are two clusters in the current research of LRER, in which one surrounds heavy metal pollution and the other focuses on ecological restoration of mining areas. The two clusters correspond to the remediation and ecological restoration (rehabilitation) stages of stepwise ecological restoration, respectively. Thematic evolution analysis shows that, for more than 30 years, mine drainage and heavy metal pollution treatment, soil reconstruction (soil profile reconstruction, soil improvement), and vegetation restoration have been the focus of research. (3) Future research should focus on the relationship between mine ecological restoration and carbon sequestration and the relationship between ecological restoration and biodiversity in mine areas. In addition, LRER technology exchange, international cooperation, and industrialization are also main directions of development. Generally, in this study, metrology software (Bibliometrix R-package 3.1.4) from the literature was used to sort out the relevant literature on LRER over the past 30 years so as to provide reference for future research on LRER. Full article

Acidithiobacillus ferrooxidans is a chemotrophic, aerobic, acidophilic, and Gram-negative bacterium that plays a key role in iron and sulfur cycling and has a wide range of applications in the industrial field. A novel A. ferrooxidans strain, hereinafter referred to as strain “YQ-N3”, was isolated from sediments of a river polluted by acid mine drainage (AMD) of an abandoned mine in Shanxi, China. The whole genome sequencing results revealed that A. ferrooxidans YQ-N3 has a 3,217,720 bp genome, which is comprised of one circular chromosome and five circular plasmids (Plasmid A, Plasmid B, Plasmid C, Plasmid D, Plasmid E). Plasmid E, a new plasmid, had not been annotated in the reference database. A. ferrooxidans YQ-N3 had a close evolutionary relationship with A. ferrooxidans ATCC23270 and A. ferridurans JCM18981 and exhibited higher similarity in its genomic structure with A. ferrooxidans ATCC23270. Multiple genes related to environmental resistance and iron and sulfur metabolism were predicted from its genome. A. ferrooxidans YQ-N3 can remarkably increase the oxidation rate of Fe²⁺ and S⁰ and enhance the hydrophilicity of S⁰, which was supported by functional gene analysis and laboratory experiments. The biological desulfurization experiment demonstrated that A. ferrooxidans YQ-N3 can reduce the sulfur content in coal by removing pyrite sulfur and organic sulfur. Full article

Governance of abandoned mines has become a pressing issue for China. The utilization of abandoned mines is a technology that can solve the problem of governance and recreate the value of mines, which is in line with the current strategic goals of ecological protection and double carbon in China. In this paper, the various utilization models and the advances in rock mechanics of abandoned mines across the globe are summarized and reviewed. The utilization models of abandoned mines can be categorized into four aspects: Energy storage, Waste treatment, Ecological restoration, and carbon dioxide (CO₂) sequestration. There are a number of applications and uses of abandoned mines, such as pumped storage, compressed air storage, salt cavern gas/oil storage construction, carbon dioxide storage and utilization, radioactive waste disposal and treatment, and tourism development. Various progress practices of abandoned mines are discussed in detail with emphasis on the national conditions of China. The basic rock mechanics problems and advances involved in the construction of the facilities related to the utilization of abandoned mines are discussed and evaluated. The establishment of relevant research and experimental platforms will contribute to the sustainable development of China’s mining industry and the improvement of clean technologies. Full article

In order to solve the problems of the uneven deformation of Gangue Filled Wall and the difficulty of large-scale promotion of roadway side support, and to achieve the purposes of direct disposal of coal mine waste, reducing costs, and protecting the environment, the failure mechanics model of the bagged gangue was established, and the mechanical action relationship between longitudinal external load and transverse external load of gangue woven bag was deduced. Through the uniaxial compression test of large-scale flexible backfill (coal gangue of different particle sizes), it was obtained that when the strain is 0.2, the bearing capacity of particles with particle sizes between 0 and 10 mm is greater than 5 MPa, and when the strain is 1.27, the bearing capacity of particles with particle thicknesses between 10 and 20 mm is greater than 0 mpa, which meets the requirements of resistance value and resistance growth rate of gob side entry. In the “load deflection” test of backfill (gangue) samples, it was found that the maximum failure load of wet shotcrete is greater than that of dry shotcrete, and the wet shotcrete can withstand greater deformation under the same load conditions. Through the analysis of the experimental results of “flexural strength thickness” and “maximum failure load thickness”, it was finally determined that the thickness of the spray layer with good flexibility and sufficient support force is controlled at about 80 mm. Full article

The number of large coal power plants, characterized by pithead plants, is increasing rapidly in major coal mining countries around the world. Overburden movement caused by coal mining and greenhouse gas emissions caused by coal thermal power generation are intertwined, and have become important challenges for mine ecological environment protection at present and in the future. In order to provide more options for green mining in large coal power plants, a large coal power base in northwest China was taken as the researching background in this paper, and a green mining model considering the above two aspects of ecological environment damages was proposed; that is, the carbon dioxide greenhouse gas produced by coal-fired power plants can be geologically trapped in goaf, whose overburden stability is controlled by backfill strips made of solid mine waste. In order to explore the feasibility of this model, the bearing strength of the filled gray brick consisting mainly of aeolian sand and fly ash under different curing methods was firstly studied, and it was discovered that the strength of the gray brick significantly improved after carbonization curing. After that, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to compare the mineral composition and its spatial morphology in gray brick before and after carbonization, and it is believed that the formation of dense acicular calcium carbonate after carbonization curing was the fundamental reason for the improvement of its bearing strength. Finally, a series of stope numerical models were established with UDEC software to analyze the surface settlement, crack propagation height and air tightness of the overlying strata, respectively, when goaf was supported by the backfilling strips with carbonized gray brick. The research results of this paper showed that the stability of overlying strata in goaf can be effectively controlled by adjusting the curing methods, width and spacing of the filled gray brick, so as to facilitate the following geological sequestration of carbon dioxide greenhouse gas in goaf. Consequently, the ecological environment damages caused by coal mining and utilization in a large coal power base can be resolved as a whole, and the purpose of green mining can be achieved as desired. Full article

Deciding on an appropriate development strategy is one of the most crucial aspects of the mining industry’s green transition. This research introduces a novel integrated decision support model that can be applied to analyze various environmental factors and determine development strategies. In this study, a strengths, weaknesses, opportunities, and threats (SWOT) analysis is employed from multiple perspectives, including political, economic, social, and technological (PEST), to assess the internal and external factors that influence green mining. The fuzzy analytic hierarchy process (AHP) is used to analyze the factor weights quantitatively, and the fuzzy Measurement of Alternatives and Ranking according to Compromise Solution (MARCOS) method is used to rank and select development strategies. According to the results, “grasp the trend of green development and improve the protection and exploitation level of mineral resources” is found to be the final optimal strategy. Comparative analysis and sensitivity analysis confirmed the accuracy of the model and the case study results. Full article

Green mining (GM) can achieve the harmonious development of mineral resource exploitation and environmental protection. Performance evaluation is the key to promoting GM. This research explores favorable methods to evaluate the green mining performance (GMP) of underground gold mines. First, according to the specific characteristics of underground gold mines, an evaluation criteria system for GM is formulated. Meanwhile, the weights are calculated using an integrated gray DEMATEL and ANP technique, which considers the correlation between indicators. Subsequently, the solution methodology for performance evaluation is proposed based on normalization of indicators. Finally, six underground gold mines are utilized as case studies to verify the methodological feasibility. The results of the empirical study show that there is a significant gap between ordinary mines and pilot green mines, and this study, via comparison analysis and cause–effect analysis, gives direction for mines improvement. Not only will the work provide technical and theoretical support for the evaluation and construction of similar green mines, it will also serve as a reference for government policy implementation. Full article

To take full advantage of the multicomponent transient electromagnetic method, we summarize the advantages of multicomponent exploration based on simulation calculation. We have carried out experiments on the effectiveness of the method in the known copper-nickel mining area. The results show that the characteristic curve of the horizontal component can effectively point to the central direction of the low-resistivity ore body and reflect the occurrence of the ore body. The degree of coupling between the vertical component and the ore body is high, which is beneficial for quantitative inversion. The results for the horizontal component and vertical component interpretations are consistent, which reduces the limitation of conventional single vertical component interpretation and effectively improves the work efficiency in field work. Full article

Longwall backfill mining effectively mitigates the height of water-conductive fractured zone (HWCFZ), preventing it from reaching the overlying aquifer and thus preserving the groundwater. However, it has the disadvantages of insufficient filling time and space as well as the mutual constraints between filling and mining. A novel continuous extraction and partial backfill (CEPB) water-preserving mining method was therefore proposed. The analytic hierarchy process (AHP) method was employed to identify the factors affecting the HWCFZ of CEPB, and five main factors, namely, the hard-rock lithology ratio, mining height and depth, and the width of the Wongawilli and protective block, were determined based on the weight distribution. UDEC software was used to establish a numerical model to simulate the HWCFZ under five factors. By using a multiple linear regression analysis of the numerical simulation results, a model for predicting the HWCFZ was established. It was applied in a colliery of the Yu-Shen mining area, and the HWCFZ was 57.7 m, 9% higher than that of borehole television logging of 53.1 m from the field measurement, indicating its rationality. Subsequently, the model was generalized and applied to the whole mining area, and the thematic map of the HWCFZ and the protective zone thickness of CEPB and longwall caving mining were obtained. The criterion for water-preserving mining based on the equivalent permeability coefficient of the protective zone is then proposed, which can provide guidance for the mining parameters optimization of the CEPB. Full article

The mining-induced water-conducting fracture zone (WCFZ) plays a critical role in roof water damage prevention and ecological protection. The measured heights of the WCFZ were collected from 52 working faces or boreholes in the Ordos Basin mining area. Four factors influencing the mining-induced height of the WCFZ, i.e., mining thickness, proportion coefficient of hard rock, working width, and mining depth, were analyzed. The optimal unitary function model of each factor and the height of the WCFZ were obtained through single-factor analysis. The grey correlation method and fuzzy ordered binary comparison method were used to determine the comprehensive weight, and the weighted improved multiple regression model was obtained by combination and iteration. The relative error of the model was basically controlled within 10%. Finally, taking the Qingshuiying Coalfield as an application case, we predicted the mining-induced height of the WCFZ by using the new prediction model. The spatial distribution characteristics of the WCFZ were analyzed by the geographic information system. In addition, Groundwater Modeling System (GMS) software was used to build a 3D structure model of WCFZ height to visualize the spatial distribution rules of the WCFZ. The results showed that the height of the WCFZ can be predicted quantitatively by this new method, and the visualization of the WCFZ can be realized. The proposed method effectively analyzes and predicts the mining-induced height of the WCFZ so that water gushing risks from overlying aquifers can be prevented or mitigated in mines. Full article

RM (red mud), which comes from the Bayer process, has a huge annual output and is harmful to the environment. Because of the high iron content in RM, the process of iron recovery from RM can reduce the amount of RM well and create economic benefits, so it is a promising process. The paper focuses on the review on the research of the iron recovery method from RM, which includes the physical recovery method, chemical recovery method and emerging recovery method. By comparing the advantages and disadvantages of these processes, it is concluded that the fluidized bed reduction is a promising process that can be rapidly applied to the industry, but it still needs more investigation to overcome the current technical difficulties in the near future. Full article

The exploitation and utilization of coal resources are not only prone to causing water table lowering, but also produce a large amount of CO₂ and coal-based solid waste. A scientific concept that employs the CO₂ and solid wastes to develop filling bodies and inject them into the mined-out area, to sequestrate CO₂ and mitigate the overburden migration and thus preserve the overlying aquifer, is proposed. Continuous extraction and continuous backfill (CECB) mining was selected as the mining method to meet the aforementioned objectives. Additionally, carbon dioxide mineralized filling body (CMFB) under ambient temperature and pressure was developed, with fly ash as aggregate, and CO₂ gas, silicate additives and cement as accessories. The uniaxial compressive strength (UCS) and tensile strength of CMFB with various curing times and fly ash contents were tested indoors. A physical analogue simulation and FLAC^3D numerical calculation were then successively implemented on the premise of determining a similar material ratio of CMFB in analogue simulation and calibrating the parameters of the CMFB in numerical simulation. The deformation of aquifuge and water level lowering while using CECB and CMFB with various proportion of fly ash were obtained. When using the CMFB with 75% fly ash content and 28 d curing time, the maximum values of vertical displacement, horizontal displacement, inclination, horizontal deformation and curvature of aquiclude were 26 mm, 6.5 mm, 0.12 mm/m, 0.08 mm/m and 0.0015 mm/m², respectively, and the water table decreased 0.47 m. The results show that the CMFB with 75% fly ash is the most appropriate ratio to realize water preservation mining, CO₂ sequestration and harmless treatment of solid wastes, contributing to the green and sustainable development of coal areas. Full article

Mining fracture is the key factor in realizing water-conservation mining, stability evaluation of coal mining subsidence areas, and accurate restoration of the surface eco-environment. To clarify, the evolution and distribution of mining fractures, based on the key strata theory and the mining degree of overburden failure, the contact state of rock stratum after overburden critical failure was analyzed, the formation mechanism of “saddle shaped” water conducting fracture zone was revealed, and the permanent mining fractures were determined to be primarily concentrated in the overburden structure at the boundary of the working face. According to the shear test of sandstone in the fracture zone, the damage degree of the rock sample was positively correlated with shear stress, and the overburden structure exhibited no instability. Based on the distribution of mining fractures, the fracture zone was divided into the original fracture, tensile fracture, structural void, and void compaction areas in the horizontal direction. The structural void area had the largest residual deformation in the goaf. A regional division method based on overburden critical failure was proposed and applied in engineering by using surface movement monitoring. The results showed that the surface subsidence near the boundary of working face was greater than that in the middle, and the residual surface deformation in the goaf was closely related to the mining time, which has long-term characteristics. The rationality of the regional division method of mining fractures was also verified. Full article