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Based on the greening and low interference disposal requirements of coal gangue in high-yield and high-efficiency mines in Inner Mongolia and Shaanxi, and by integrating the existing theories and technologies such as underground filling technology of coal gangue, mine yellow mud grouting technology, and the evolution law of mining overburden fractures, a technology of filling goaf with coal gangue slurry for green disposal of coal gangue is proposed. The principle and technical framework of the technology of filling goaf with coal gangue slurry are clarified. This paper expounds on the technological process of technology of filling goaf with coal gangue slurry, establishes three types of slurry filling systems, such as centralized ground layout, ground and underground coordinated layout, and centralized underground layout, and constructs three slurry filling methods, including low-level grouting, adjacent level grouting, and high-level grouting, forming seven kinds of technology models of filling goaf with coal gangue slurry, including ground centralized pulping + high-level grouting, ground centralized pulping + adjacent grouting, ground centralized pulping + low level grouting, ground and underground coordinated pulping + adjacent grouting, ground and underground coordinated pulping + low level grouting, underground centralized pulping + adjacent grouting, and underground centralized pulping + low level grouting, and gives the selection process of technology models of filling goaf with coal gangue slurry. Based on the different conditions and requirements of Haidaze Coal Mine and Huangling No. 2 Coal Mine, engineering tests were carried out on two different technology modes, namely, ground and underground coordinated pulping + low level grouting and ground and underground coordinated pulping + adjacent grouting, based on simulation tests of low level grouting and adjacent grouting. The tests prove the feasibility of filling goaf with coal gangue slurry and explore the way for the theoretical research of the technology of filling goaf with coal gangue slurry and greening and low interference disposal of coal gangue. [ABSTRACT FROM AUTHOR]

Filling mining is the main mining method in coal mine, and its safety is the pillar of the overall safety of the mine. Filling mining can effectively protect the surface environment, better solve the problem of ground pressure, and maximize the recovery of underground resources. Therefore, this method has an irreplaceable role in deep mining of coal mines and is highly valued by the mining industry all around the world. In order to evaluate the implementation effect of filling mining, a comprehensive weighting-set pair analysis safety evaluation model is established. This model optimizes the subjectivity of analytic hierarchy process (AHP) and the objectivity of Entropy Weight Method (EWM) in traditional methods. Besides, we add experts' weight to Entropy Weight Method. The combination of the two methods makes the index weight more reasonable and effective, and can more fully reflect the difference and correlation of index. Firstly, the accident causation analysis and taxonomy (ACAT) is used to find out the accident causation factors of filling mining, and then, the AHP and EWM are used to determine the weight of each evaluation index from different perspectives. Then, the evaluation group is established to score the importance of each expert, so as to reduce the subjectivity of expert scoring. Finally, according to the principle of set pair analysis, the safety evaluation model of filling mining is applied to Yuxing Coal Mine in Inner Mongolia. The evaluation result shows that the safety grade of this mine is grade 1 "safety." This paper provides a new way and direction for the comprehensive evaluation of similar mining methods, the establishment of index system, the acquisition of index weights, and the evaluation of safety level, which has promotion and application value. [ABSTRACT FROM AUTHOR]

High-intensity coal mining in grasslands has negative impact on the surface ecology of the mining area and its surroundings. This impact shows spatio-temporal heterogeneity due to differences in mining intensity at various life stages. Based on remote sensing images and experimental test data, this paper took the Baorixile Surface Coal Mine (BSCM), which as the largest open-pit mine in eastern Inner Mongolia, as an example to analyze surface ecological quality and risk at the whole life cycle. In total, 13 indices from three aspects of site structure, spatial pattern, and ecological function were selected to assess surface ecological quality. The geoaccumulation index and potential ecological risk index were used to analyze the ecological risk of surface soil. Identification of impact range of mining activities and pollution sources of soil heavy metal was obtained by correlation analysis. At present, the BSCM is at a stable stage. Ecological quality showed a deteriorating trend during the reaching and stable stages. The soil organic matter content at the BSCM was lower than the Second National Soil Survey and exhibited a decreasing tendency. A low ecological risk was found in soil, and Cd was the main potential ecological risk element. The surface ecology of the boundary and its 2 km buffer zone was affected by mining activities in the BSCM. Mining activities may have an impact on the surface ecology of the 5 km buffer zone. This study provides a reference method for ecological quality assessment and impact scope determination of similar mining areas. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of roof strata conditions, shield pressure, and ground surface subsidence above Panel 42105 of the Buertai Coal Mine in Inner Mongolia, China. A 3D geological model and a 2D numerical simulation model are established to examine the roof strata structures with varying strata conditions. Numerical simulation results demonstrate that the hard rock 1 and 2 roof layers are, on average, likely to break 20 m and 57 m behind the coal face, respectively. It is concluded that when the immediate roof is relatively thin, a cantilever beam is formed, whereas a Voussoir beam is formed when the immediate roof is relatively thick. The patterns of shield pressure and surface subsidence under different roof conditions are also examined. The shield working pressure under the Voussoir beam structure appears to be lower than that under the cantilever beam structure. The average horizontal distance behind the working coal face at which the maximum surface subsidence occurs is 92.1 m. On-site monitoring data are used to explain the causes of the unusual shield pressure and its relation to surface subsidence. Finally, guidelines to predict the shield pressure under similar conditions are provided. [ABSTRACT FROM AUTHOR]

A large number of burnt rocks in some open-pit mines in Xinjiang, Inner Mongolia and Ningxia have a great influence on the blasting effect. For this kind of rock, through the analysis of physical and chemical changes, combined with ANSYS/LS-DYNA and PFC 2D numerical simulation software, a burnt rock model with multiple joint cracks and irregular distribution is constructed to simulate the blasting process of burnt rock under the combined action of stress wave and detonation gas. The results show that the fracture of rock mass affects the propagation of blasting cracks in the fracture area, resulting in stress concentration and stress hindrance. The action time of stress wave is reduced, and the energy of blasting gas is partially absorbed by the fracture, resulting in uneven stress on the burnt rock bench and seriously affecting the bench blasting effect. [ABSTRACT FROM AUTHOR]

The Wuda coalfield in Inner Mongolia is a vital coal base in China, and it is the hardest-hit area for coal fires (spontaneous combustion of coal seams and coal gangue). Using gas chromatography–mass spectrometry, this work tested the concentration and analyzed the characteristics, distribution, sources, and health risks of polycyclic aromatic compounds (PACs) in the surface soil of the Wuda District, including the coal mine, coal fire, agricultural, and background areas. The soil of coal mine and coal fire area were heavily polluted with PACs, with mean concentrations of 9107 and 3163 µg kg−1, respectively, considerably higher than those in the agricultural (1232 µg kg−1) and background areas (710 µg kg−1). Alkyl polycyclic aromatic hydrocarbons (APAHs) were the dominant pollutants among these PACs, accounting for 60–81%. Alkyl naphthalenes and alkyl phenanthrenes are the primary pollutants in APAHs, accounting for 80–90% of the total amounts. Additionally, using the positive matrix factorization method, it can be concluded that the primary PAC sources are petrogenic sources, coal and biomass combustion, coal fires, and vehicle emissions. Finally, according to the cancer risk values of 16 PAHs, only the coal mine area showed a potential cancer risk. However, this result lacks a risk assessment of APAHs and underestimates the actual risk. The results of this study improved the understanding of PAC pollution in coal fire and surrounding areas and provided a reference for environmental and health risk investigations. [ABSTRACT FROM AUTHOR]

Groundwater (GW) is an important source of freshwater in arid and semiarid areas. Some important industrial activities, such as coal mining, also consume GW. There have been few studies evaluating GW quality in the Selian coal mining area of Inner Mongolia. This study aimed to identify the hydrochemical phases and the sources of main ions in the GW of the Selian coal mining area. Water quality analysis was performed on 20 shallow GW samples collected from the study area. Statistical correlation analysis was performed on these water quality data. The quality of irrigation water was evaluated based on water quality indices such as the sodium absorption rate and sodium percentage. The risk of nitrate pollution in the study area to human health was evaluated by GW nitrate content. The results show that the dominant GW chemistry types in the study area are the mixed and Ca–HCO3 types. Correlation analysis indicates that rock weathering and leaching are the main natural drivers of GW hydrochemistry in this area. The irrigation risk analysis shows that GW in this area can be used for irrigation, although some caution is needed. The human health risk assessment shows that GW nitrate pollution poses more risk to children than to adults by a factor of 1.168. It is recommended that centralized treatment of drinking water is the optimal approach to managing this risk. The results of this study can act as a reference for the rational use of GW and for control of nitrate pollution in this area. [ABSTRACT FROM AUTHOR]

To better understand water inrushes originating from shaft-freezing holes, the hydrogeological conditions and water source were analyzed for a typical inrush case in the Yingpanhao coal mine in western China. The mechanism of this new type of water inrush was identified by considering the stratum movement caused by mining, the concentric annular channels of freezing holes, and the dynamic recharge of multiple aquifers. A new risk assessment model and corresponding grouting method were developed and the problems involving the prediction of water inrush and selection of the optimum grouting position were described. Detailed guidelines for grouting, including the layout of injection boreholes, slurries, grouting pressure and stopping criteria, were proposed. A grouting case targeting this type of water inrush in the Yingpanhao coal mine was introduced. Field studies indicated that open, concentric annular freezing hole channels provide favorable conditions for groundwater migration. The proposed method may effectively inhibit groundwater migration in multiple aquifers and prevent water inrushes through shaft freezing holes and provides an appropriate framework for water inrush prevention for similar mining areas in western China. [ABSTRACT FROM AUTHOR]

The development and use of intelligent drilling rigs make it available to obtain accurate lithology data of blast drilling. In order to make full use of drilling data to improve blasting efficiency, the following research was carried out. First, a database is established to manage and store the blast hole data recognized by the intelligent drill. Secondly, the blast hole lithology data is taken as a sample, and the inverse distance square method is used to interpolate the blasting range's solid elements to generate a three-dimensional solid model of the blasting rock mass. Afterward, the blasting range polygon and stope triangle grid are used successively in the solid model to obtain the cut 3D solid model of the blasting rock mass; finally, the blast hole charge is calculated based on the cut 3D solid model of the blasting rock. The C++ programming language is used to realize all the blast hole charge amount processes based on the three-dimensional solid model of the blasting rock mass. With the application example of No. 918 bench blasting of Shengli Open-pit Coal Mine in Xilinhot, Inner Mongolia, the blast hole charge amount in the blasting area is calculated and compared with the results of single hole rock property calculation, the results show that the blast hole charge calculated by three-dimensional rock mass model can be effectively reduced. [ABSTRACT FROM AUTHOR]

Aiming at the problem of mining coal resources under the Yuxing Mine Ecological Park in Inner Mongolia, China, we adopted a continuous mining and continuous backfilling (CMCB) cemented-fill mining method; based on the systematic description of the mining and backfilling craft of the CMCB mining process, comprehensive use of theoretical analysis, numerical simulation, and similar simulation test methods to analyze the control mechanism of overlying strata. By establishing the mechanical model of roof movement for the CMCB mining, the roof deflection curve equation is deduced, and the roof instability criterion is put forward based on the maximum tensile stress criterion. Numerical simulation showed that the stress curve at the shallow part of the roof fluctuates up and down in a "w" shape, the stress curve of the upper surrounding rock sinks slowly, and the coal pillars and filling bodies are alternately loaded during the staged mining process to jointly limit the movement of the overlying strata. The similar simulation test results showed that the roof has no structural damage, the roof cracks are not obvious, and the overlying strata control effect is good. On site tests showed that the CMCB mining method can effectively limit the movement of the overlying rock in the stope, control the surface subsidence of the ecological park, and increase the recovery rate of coal resources. It can provide a reference for the development of coal resources and ecological protection in a fragile environment. [ABSTRACT FROM AUTHOR]

Short wall mining technology is an important method to coal resource mining in the United States, Australia and other countries, and also one of important methods to boundary coal resource recovery in China. Short wall mining technology through leaving a large number of coal pillars to support and control roof, induces a series of accidents, such as large area roof suspended, collapse and shock, which restricts the further popularization and application of short wall mining technology seriously. By improving the existing short wall mining technology, the article proposed short wall continuous mining technology with full roof falling, and designed measures to control roof. The main research work is as follows: (1) By reducing and eliminating coal pillars in mining section as much as possible, including entry protecting pillar and pillar between caverns, also ensured stability of roof during mining period at the same time; after mining, roof can be collapse, to prevent large area roof suspended and collapsed inducing shock accidents; mining process and equipment of short wall continuous mining technology with full roof falling, were designed comprehensively. (2) Measures to control roof of short wall continuous mining technology with full roof falling are designed, using self-moving hydraulic support to control roof of mining cavern, anchor bolt and cable to ensure branch and cross entries stable during mining period, and forced caving technology to control large area roof suspended; (3) Short wall continuous mining technology with full roof falling and roof control measures were successfully industrialized in 42,210 boundary coal face of Yujialiang coal mine, which belong to Shenhua energy group in Inner Mongolia. The research result is significant to enrich and develop short wall mining technology. [ABSTRACT FROM AUTHOR]

Asymptotically correct simultaneous confidence bands (SCBs) are proposed in both multiplicative and additive form to compare variance functions of two samples in the nonparametric regression model based on deterministic designs. The multiplicative SCB is based on two-step estimation of ratio of the variance functions, which is as efficient, up to order n - 1 / 2 , as an infeasible estimator if the two mean functions are known a priori. The additive SCB, which is the log transform of the multiplicative SCB, is location and scale invariant in the sense that the width of SCB is free of the unknown mean and variance functions of both samples. Simulation experiments provide strong evidence that corroborates the asymptotic theory. The proposed SCBs are used to analyze several strata pressure data sets from the Bullianta Coal Mine in Erdos City, Inner Mongolia, China. [ABSTRACT FROM AUTHOR]

Water-bearing structures in front of coal mine shaft drivages require effective advanced prediction. Based on the characteristics of coal field logging curve carrying rich geological information, it is introduced into the advanced prediction of water-bearing bodies in mine shafts. At the same time, mine geophysical prospecting technology, such as the DC resistivity method, can accurately and effectively track and detect geological conditions during mine shaft drivage. The proposed advanced prediction method of the borehole-ground electrical method based on the detailed interpretation of logging curves was experimentally studied using physical simulations of the detailed interpretation of water-bearing rock strata in logging data and geophysical advanced detection simulations of water-bearing structures in mine shafts. By constructing a physical model of the mine shaft drivage, the change in the water content of the rock strata is simulated by adding water to sand and gravel, and the apparent resistivity logging in a borehole is simulated. The water-bearing characteristics of the model under different water content conditions are interpreted by using 3-D visualization technology, and it is concluded that the change law of the electrical characteristics of sand and gravel after adding water is a logarithmic function relationship. Then, based on the results of the detailed interpretation of the logging curves, a model experiment using the DC resistivity method of ground-borehole joint advanced detection is carried out, and the response characteristics of changes in the model water diffusion resistivity are accurately detected. In addition, a shallow geological borehole is constructed in the field. Water injection in the borehole causes anomalous changes in the electrical properties of the strata around the borehole and simulates water-bearing structures at different depths and layers, which verifies the effectiveness of the borehole-ground electrical method in detecting water-bearing structures in front of mine shaft drivages. The simulation results show that the advanced prediction method of borehole-ground electromagnetic technology based on the interpretation of logging curves enhances the effectiveness and detection efficiency of advanced detection and prediction of the water-bearing characteristics of rock strata. Based on the logging curve, the water-bearing characteristics of the strata in front of a coal mine shaft drivage in the Dongsheng coalfield in Inner Mongolia are interpreted in detail, and the provided anomalous target areas can provide reliable guidance for advanced detection using the borehole-ground electrical method in the future. [ABSTRACT FROM AUTHOR]

Rapid identification of inrush water sources is vital for the safe operation of a coal mine. Hydrogeochemical (fuzzy comprehensive evaluation method and cluster analysis method) and isotope analyses are applied to identify the inrush water sources of the Mindong No. 1 mine, which is located in north-east Inner Mongolia, China. The clustering analysis and isotope analysis results show that the inrush water sources are from aquifer 1 (A1), aquifer 2 (A2) and Yimin river. However, fuzzy comprehensive evaluation shows that the inrush water sources are from A2, aquifer 3 (A3) and Yimin river. Considering the hydrogeological conditions of the study area, it is concluded that the inrush water sources are A1, A2 and Yimin river, with mixing ratios of 30.8%, 60.6% and 8.6%, respectively. The application of multiple methods makes the conclusion more reliable. Additionally, this study improves the speed and effectiveness of the identification of inrush water sources in coal mines and provides a practical reference for research related to mine water inrush to ensure the safe operation of coal mines. [ABSTRACT FROM AUTHOR]