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There are many dissolved salt caverns in China, but most of the existing caverns cannot be used for gas storage directly, especially the huge number of horizontal old caverns. First, situations of the main existing old salt caverns in China were investigated, including the burial depth, thickness of the salt formations, grade of the salt layer, number of existing caverns, mining methods and inferred cavern shapes. Then, a typical process for screening and evaluating existing salt caverns was proposed, and then a new reconstruction method by drilling new wells between injection and production wells was introduced. Thirdly, theoretical analysis methods that can be used to evaluate the geotechnical feasibility of horizontal salt caverns were summarized. Finally, numerical simulation was carried out to study the geotechnical feasibility of the reconstructed horizontal cavern and the influencing law of the specific reconstructed measures. Some conclusions were drawn as follows: (1) For the reconstruction of horizontal salt cavern by drilling a new well between injection and production wells, the size of the newly solved cavern, operation time and internal pressure are the three most important influence factors; (2) Combined with the numerical simulation results, the surrounding rock of the horizontal cavern should mainly focus on the tensile and shear failure around the cavern and the instability of the key roof; (3) Compared with the method of drilling new wells outside the cavern, drilling new wells between wells are different in the displacement scope, volume shrinkage and plastic zone distribution. In summary, the introduced reconstruction can enlarge the small volume of existing horizontal old caverns, but more in-depth research and field engineering practice are needed to optimize the reconstruction method. [ABSTRACT FROM AUTHOR]

This study uses a data-driven approach to mine the distribution of personality traits among Chinese people in the Chinese social context. Based on the hypothesis of personality lexicology, word embedding technology was employed in machine learning to mine personality vocabulary from Tencent's word embedding database. More than 10,000 Chinese personality descriptors were extracted and analyzed using Gaussian Mixture Model Cluster and Hierarchical clustering analysis. The data was collected from 658 Chinese people randomly from all parts of China through an online questionnaire method. The results reveal six personality traits in the Chinese context, expanding the personality thesaurus and providing examples to illustrate each trait. The findings coincide with previous research on the five-factor model, which partially describes the personality traits of Chinese people, but does not offer a complete explanation of their typical social behavior patterns. Additionally, the study supports the notion of cultural particularity in personality traits. The approach used in this study offers a richer personality vocabulary than traditional personality mining methods, and word embedding technology captures richer semantic information in Chinese. The six Chinese personality traits identified in this study will also be used to explore how to quantify and evaluate personality traits based on word embedding and personality descriptors. [ABSTRACT FROM AUTHOR]

Coal is one of the primary energy sources in China. Due to different mining processes, the environmental impact of each mining method varies. Traditional mining methods have relatively low costs but a substantial ecological impact. For example, backfilling mining is environmentally friendly but raises mining costs for surface settlement, coal gangue solid waste pollution, etc. Therefore, to meet the current sustainable development concept, based on the principles of coal mining, a novel economic benefit calculation modeling applied to coal mining is presented to analyze the economy's differential benefits under different mining methods and their impact on the environment. First, a model was established to investigate the economic benefits of coal mining. Secondly, the differential benefits under three mining methods, collapse mining, cemented backfill mining and material-improved cemented backfill mining were calculated for a mining site in China as an example. Finally, four crucial factors affecting coal mine efficiency were identified using hierarchical analysis, the intersection of the differential benefits of the three mining methods under the four essential factors was derived, and the degree of influence of the vital factors on the economic efficiency of coal mines was analyzed using the univariate method. The differential benefits of the material-improved cemented backfill mining method are more prominent than the other two mining methods, with an overall economic increase of about 8%. Coal reserves, the national coal tax reduction rate and the differential benefits of coal mines show a significant positive relationship. The model applies to all types of coal mines and can be used to select low-consumption, low-cost and high-yield mining methods according to the actual situation of coal mines and local policies, guiding the formulation of government policies and the selection of mining methods for coal mining enterprises, which is of great significance to the sustainable development of the environment and the rational exploitation of energy. [ABSTRACT FROM AUTHOR]

A considerable number of coal mines employed room and pillar mining in the last century in northern China, where the goaf remained stable for a period of time; however, with the increased exposure of coal pillars, their collapse may gradually increase. The stability assessment of these old rooms and pillar goafs is challenging due to their concealment, irregular mining patterns, and the long passage of time. The methodology developed in this study, based on "space-sky-earth" remote sensing such as InSAR to trace historical deformation, the UAV observation of current surface damage, and comparison of mining spaces, can rapidly detect on a large scale the collapse of old goafs and the trend of damage. This study is conducted with an example of a coal mine in Yulin, Northern China, where obtained quantitative surface deformation values were integrated with qualitative surface damage interpretation results, followed by a yearly analysis of the overlying rock movement in accordance with the underground coal mining process. The results show that from 2007 to 2021, corresponding surface deformation and damage occurred following mining progress. However, the room and pillar goaf areas had not undergone any surface deformation, nor had there been incidents of landslides or ground fissures; therefore, it was speculated that no roof collapse had occurred in this region. The surface deformation and damage associated with underground coal mining are complex and influenced by the coal seam occurrence, mining methods, strata lithology, terrain slope, temporal evolution, and anthropogenic modifications. These phenomena are representative of the coal mining area, and this methodology can provide a reference for similar endeavors. [ABSTRACT FROM AUTHOR]

Backfill coal mining technology has drawn widespread attention due to its benefits of "controlling surface deformation and subsidence, reducing mining-induced disturbance in the stope, and recycling solid mine wastes". However, the backfill coal mining technology is still progressing slowly in China. The geological environment of China's mining areas is complex and highly diversified, and backfill coal mining is expected to fulfill different goals in a wide range of engineering scenarios. These facts explain the poor reproducibility of backfill coal mining projects. This study reviews the existing backfill coal mining systems in China. Based on findings from a survey of engineering cases, we summarize five types of new backfill coal mining methods classified by deployment style; namely, borehole grouting backfill, roadway backfill, borehole–roadway backfill, in situ backfill, and roadway-in-situ backfill. A total of 15 backfill coal mining methods falling into the above five categories are described. An engineering design workflow for backfill coal mining consisting of five steps is proposed; namely, identifying the targets of backfill, analyzing the feasibility of deploying the backfill system, comparing the engineering quantities of different engineering schemes, estimating the economic efficiency of backfill, and backfill performance tracking and monitoring. Real cases of backfill engineering design are analyzed to inform the fast and reasonable design of backfill strategy for specific working faces in certain coal mines. [ABSTRACT FROM AUTHOR]

To quantitatively evaluate the carbon emission effects of various underground mining schemes in metal mines, a carbon emission calculation model specifically for underground metal mines was established. The carbon emissions stemming from the mine's production process were categorized into three components: carbon emissions from the production of consumed materials, fuel, and electricity; carbon emissions resulting from fuel combustion and explosive explosions, and the reduction of CO2 absorption due to the occupation of the surface industrial site. Subsequently, the carbon emission impact of underground metal mines was assessed using an example from an iron mine in Anhui Province, China. The results showed: (1) Among the underground mining processes, electricity consumption emerged as the primary source of carbon emissions. This underscores the potential for significant carbon emission reduction through the implementation of innovative electric power technologies in underground metal mines. (2) Mining methods with higher productivity showed clear advantages. They not only contribute to the reduction of carbon emissions per kiloton of ore from multiple perspectives but also led to a shorter mine lifespan and decreased CO2 absorption by woodlands occupied by the surface industrial site. Furthermore, these methods resulted in lower carbon emissions throughout the mine's lifespan. (3) Backfill mining proved to be effective in curbing tailings emissions and reducing the required area for a tailings pond. Consequently, this approach minimizes the CO2 absorption by woodlands occupied by the tailings pond. [ABSTRACT FROM AUTHOR]

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

Despite China's position as a global mining powerhouse, tens of thousands of small- and medium-sized mines (SM mines) within the country continue to pose potential safety hazards and environmental pollution risks. Only through the identification of suitable development paths can these mines improve their economic and environmental benefits, ultimately driving significant progress in China's mining industry. Backfill mining, an environmentally friendly mining method, has emerged as a viable solution, offering the potential to ensure mining safety, reduce environmental pollution stemming from tailings stockpiles, and enhance ore resource recovery. This review article aims to provide researchers and readers with a comprehensive understanding of the current situation and challenges faced by SM mines in China. It explores the mining processes, technologies, and equipment commonly employed by these mines while addressing the specific problems and challenges they encounter. Furthermore, the article offers recommendations to guide the future development of SM mines. Additionally, the review examines the prospects and potential applications of backfill mining methods within the context of SM mines in China, emphasizing their role in promoting sustainable mining practices, environmental protection, and waste utilization. Ultimately, this comprehensive review article serves as a valuable resource, stimulating discourse and encouraging experts and scholars to further explore the unique challenges and opportunities associated with SM mines. By highlighting the significance of green mining practices, environmental protection, backfill mining, and waste utilization, the article aims to inspire innovative solutions and foster sustainable practices within the Chinese mining industry. [ABSTRACT FROM AUTHOR]

Sustainable development in coal mining requires a continuous and efficient method of coal extraction. Research shows that gob-side entries retained through roof cutting retained gob-side (RCGE) are vital for improving mining efficiency, enhancing coal recovery rates, and enabling continuous production. However, the mechanism of surrounding rock deformation during close-distance co-mining of coal seams with this technique is not yet clear. For the Jiaokou coal mine in China, due to an unreasonable stagger distance between upper and lower working faces, the gob-side entries retained at the 9102 tailgate and 10102 headgate experience severe rock pressure, leading to significant prop damage and a sharp reduction in the cross-section of the entry. This greatly hampers the reuse of these entries. To investigate this issue, we established a model to study the stress distribution of surrounding rocks at different stagger distances (20 m, 40 m, 60 m, 80 m, and 120 m) through numerical simulation and optimized the support parameters for the retained entries. Our research found that when the subsidence of the roof in the upper coal seam exceeds 0.74 m but is less than 1.33 m, there is sliding instability in the mining body. When the subsidence exceeds 1.33 m, the mining body will rotate and deform, causing significant mining pressure within the retained entry. A stagger distance of 40 m between the upper and lower working faces can reduce pressure on the face during the mining of the lower coal seam. Extensive field measurements of rock pressure revealed that the damage rate of the single column in the gob-side entries of the upper and lower coal seams does not exceed 5% and 1%, respectively. In summary, this study provides a practical method to reduce damage to entries during the mining process, thereby increasing the continuous production capability of the coal mine. This is critical for the sustainable development of coal mining. [ABSTRACT FROM AUTHOR]

A hybrid method based on the structural equation model (SEM) and a fuzzy cognitive map (FCM) was developed to study the influences of the construction safety risks (CSR) of metro tunnels constructed by the mining method on the project risk (PR). An SEM was used to identify and verify the correlations between the CSR and PR. An FCM was developed adopting the verified standardized causality and path coefficient in the SEM. On this basis, predictive reasoning and diagnostic reasoning were performed in the framework of an FCM to simulate the CSR and PR. The feasibility of the developed method was validated based on the construction project of a metro tunnel in Wuhan City, China. The results show that (1) the cause concept node C2 (tunnel excavation) shows the strongest positive correlation with the target concept node CT (PR). According to their risks, the construction stages are ranked in descending order as C2 (tunnel excavation), C1 (advanced support), C6 (auxiliary measures), C4 (structure waterproofing), C3 (primary support), and C5 (secondary lining). (2) The target concept node CT is most sensitive to changes in the cause concept nodes C2 and C1. (3) Close attention should be paid to key risks, such as X9 (over-excavation and under-excavation) and X8 (unreasonable determination of excavation footage and sequence) in stage C2. Originality and significance: (1) A hybrid method that can simulate the dynamic interaction between the CSR and PR is proposed. (2) A new perspective for the dynamic evaluation of a PR is provided. (3) The method can be used as a decision-making tool for controlling the PR. [ABSTRACT FROM AUTHOR]

With the increasing proportion of close-distance coal seam mining in China, the problem of strong mining pressure during the mining of close-distance coal seams is becoming more and more severe. This article focuses on the complex stress environment and severe mining pressure encountered in the mining of thick coal seams under the multi-coal-seam goaf of Zhunnan Coal Mine. By using research methods, such as similar material simulation, theoretical analysis, and numerical simulation, it studies in depth the instability characteristics of the overlying rock structure of the W1701 working face, the inducing factors and mechanisms of strong mining pressure during the mining process, and control measures. The results show that the roof structure of the W1701 working face can be divided into "high-level key layer (hard rock)–giant thick soft and weak rock group–low-level key layer (hard rock)", and the law of mining pressure manifestation presents a small cycle formed by the instability of "masonry beam" structure and a main large cycle formed by the periodic penetration and step-down of the giant thick soft and weak rock group, with the load on the support during the large cycle up to 5.4 times the rated working resistance. In addition, this article proposes the strategy of using layered mining to control the manifestation of strong mining pressure under the "hard sandwiched soft" overlying rock condition of the Zhunnan Coal Mine, optimizes the thickness of the layered mining of the thick coal seam, and finally, determines the upper layer thickness of 2.8 m and the lower layer thickness of 4 m, inducing the giant thick soft and weak rock formation to undergo incremental damage and releasing the fracture energy incrementally, effectively controlling the manifestation threat of strong mining pressure in the mining of thick coal seams under the close-distance coal seam goaf. As the proportion of close-range coal seam mining increases in China, the problem of strong mining pressure during the mining of close-range coal seams becomes more severe. This article focuses on the complex stress environment and severe mining pressure in the mining of thick coal seams under multiple mined-out areas in the Zhunnan coal mine. Similar material simulation, theoretical analysis, and numerical simulation methods were used to conduct in-depth research on the unstable characteristics of the overlying rock structure of the W1701 working face, the causes and mechanisms of strong mining pressure during the mining process, and control measures. The results show that the roof structure of the W1701 working face can be divided into "high-level key layer (hard rock)–thick soft weak rock group–low-level key layer (hard rock)." The law of mining pressure manifestation presents small cycles of instability formed by "block beams" and main cycles of pressure formed by vertically cracked periodic penetration and step sinking of the thick soft weak rock group. Moreover, during the main cycle of pressure, the load-bearing capacity of the support is up to 5.4 times the rated working resistance. Furthermore, it is proposed to use hierarchical mining to control the manifestation of strong mining pressure in the "hard-inlaid soft" overlying rock condition of the Zhunnan coal mine and optimize the thickness of layered mining of thick coal seams. Ultimately, the upper layer thickness was determined as 2.8 m; the lower layer thickness was determined as 4 m, and the layered mining induced the thick soft weak rock group to undergo gradual damage and energy release, effectively controlling the threat of severe mining pressure during the mining of thick coal seams under the close-range coal seam mining. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The prediction and control of roof water disaster has been one of the key problems in the mining process of coal resources. With the increase of mining depth in the western mining area, the roof caving and communicating to the overlying water-bearing strata have led to an increasing number of roof water inrush accidents and deterioration of production environment of the working face. Aiming at the problem of roof water disaster prediction of sandy-argillaceous structural strata in Shanghaimiao mining area in China, firstly, the mechanical structure model of roof water inrush was built according to the parameters in the advance of the working face, and the thickness of the sandstone was used as the main controlling geological factor; the formula was derived for calculating the water-rich intensity F zh of the overlying strata in the mining area. Secondly, starting from the height of the "Breakage-arch" development disturbance by combining the mechanical structure model of roof water inrush, the relative positional relation of the "Breakage-arch" and the water-bearing strata was analyzed, and a new method for judging the risk coefficient T W of roof water inrush was proposed. Finally, according to the geological drilling histogram and the field conditions of #111084 working face of the no. 1 mine in Shanghaimiao mine area, the water-rich index and water inrush risk coefficient of overlying water-bearing strata were obtained by means of discriminant analysis, and the water inrush risk of #111084 working face was evaluated and predicted quantitatively. The water-rich property evaluation of water-bearing strata under the condition of low degree of hydrogeological exploration was evaluated accurately and reasonably, and a new evaluation method of the water disaster during mining was proposed. [ABSTRACT FROM AUTHOR]

With the increase of mining depth, disaster degree of rock burst in fault-controlled area is becoming more and more serious. To analyze mechanism and control method of fault rock burst, No. 3316 mining face controlled by No. 3DF56 fault in Jining mine, China, is selected as case study. First, by analysis of general situation of the mining face, mechanical characteristics of coal rock, and micro-seismic events, it is determined that the coal seam has the possibility of rock burst in the process of the face mining towards the fault. Second, based on strength theory of rock, criterion of fault shear instability is obtained, and influence of cohesion and friction angle on the stability of fault is analyzed, and it is concluded that improving the cohesion of rock can control the fault slip. Third, by borehole detection recorder, it is determined that fracture areas of fault surrounding rock distribute in the range of 0–4 m from the surface of roadway surrounding rock and 0–5.0 m from the fault. Finally, control method of "precise grouting to couple shallow and deep boreholes" is introduced, and the grouting borehole scheme is optimized. Field test results show that the method can improve the compressive strength of coal rock and distribution laws of micro-seismic events, weaken the possibility of fault slip, effectively control the deformation of roadway surrounding rock and improve the control effect of rock burst. It can provide a reference for other coal mines with similar geological conditions. [ABSTRACT FROM AUTHOR]

As an energy-intensive industry, the energy and environmental issues of non-ferrous metals industry receive increasing attention. Dividing the production of non-ferrous metals into two sub-stages including mining and processing (M&P) and smelting and pressing (S&P), a non-cooperative game network data envelopment analysis model with double viewpoints (optimistic and pessimistic) is developed to evaluate the energy and environmental efficiency of China's non-ferrous metals industry. Moreover, we construct a novel network Malmquist productivity index to identify the dynamic evolution of energy and environmental performance. The results of 25 provinces over 2010–2017 show that energy and environmental efficiency of China's non-ferrous metals industry is very low during the study period, and the efficiency gap of two sub-stages increases significantly over time. Additionally, the energy and environmental efficiency in eastern region is more affected by the M&P sub-stage, while the efficiency of that in central and western regions is greatly influenced by the S&P sub-stage. Technical progress plays a key role in the productivity improvement of the M&P sub-stage, but the main driving force of productivity change in the S&P sub-stage is different in the three regions. Based on above findings, several targeted policy implications are suggested to prompt the sustainable development of China's non-ferrous metals industry. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Since the 1990s, sandstone-type uranium in the northern basin of China has become the main target for mining. Uranium mining can cause a series of impacts on the environment. A conceptual model of the geo-environment for sandstone-type uranium in northern China was described, which covers the changes in the geo-environmental characteristics in the natural state, in the mining process, during decommissioning and after treatment. Sandstone-type uranium is mainly distributed in the Songliao, Erlian, Ordos, Turpan–Hami and Ili Basins, which have arid climates and poor stratum permeability. Pitchblende is the main uranium-bearing mineral and is associated with iron, copper, coal, organic matter and other minerals. The mineral often has a low ore grade (0.01–1.0%) and high carbonate content (2–25%). Uranyl carbonate accounts for more than 90% of the total uranium in groundwater. The uranyl content is closely related to the TDS. The TDS of groundwater in the eastern and central ore belts is usually lower than 2 g/L, while in the western region, such as Xinjiang, it can exceed 10 g/L. In situ leaching (ISL) is the main mining method that results in groundwater pollution. Acid leaching leads to a pH decrease (<3), and heavy metals represented by U and Fe exceed the background values by hundreds of times, resulting in groundwater pollution. CO2 leaching is more environmentally friendly, and the excess ions are usually Ca2+, Mg2+, NO3− and HCO3−. Soil chemical anomalies originate mostly from wind erosion and precipitation leaching of decommissioned tailings. Uranium pollution is mainly concentrated within 20 cm of the surface, and the exceedance generally varies from two to 40 times. During ISL, a series of environmental measures will be taken to prevent pollution from being exposed to the surface. After treatment, the decommissioned uranium mines will likely have no impact on the surrounding environment. In the future, the protection of groundwater should be strengthened during production, and remediation methods based on electrokinetic, microbial and permeable reactive barrier (PRB) technology should be further researched. [ABSTRACT FROM AUTHOR]

The overlying weakly cemented, and poorly performing strata in Jurassic mines of western China have mechanical properties that are generally lower than those in the Carboniferous-Permian coal mines of central and east China. During coal mining, the overlying strata easily deform and fracture. These then formed water-conducting channels, triggering a series of eco-environmental issues, including ground fracturing, collapsed surfaces, declined underground water levels, deserted lands, and even severe water/sand burst accidents. To study the fracture characteristics of weakly cemented overlying strata and the evolution law of water-conducting fractures in Jurassic coal mines in western China, this study selected Tashidian Erjingtian Mine in Korla, Xinjiang, as the research object. Based on the simulation data obtained with physical analog model testing and field monitoring results, the authors investigated the development of water-conducting fractures in the weakly cemented overlying strata during the coal seam mining process. We simultaneously determined the location of key strata in the working face based on key stratum theory. According to the present research results, key strata controlled the development height of water-conducting fractures. When the primary key stratum or sub-key stratum was not fractured, the development of water-conducting fractures was stagnant; water-conducting fractures developed abruptly when the primary key stratum or sub-key stratum was cracked. The heights of water-conducting fractures in the weakly cemented overlying strata of western China exceeded that of similar stopes of central and east China. These research results provided theoretical and technical support for safety in production at Tashidian Coal Mine. In addition, they offered a reference for green and safe production in Jurassic coal mines of western China. [ABSTRACT FROM AUTHOR]

Based on the field conditions of Huojitu Coal Mine of Shendong coal field in Northern China, eight dynamic numerical models are developed to examine the interaction between the shield and surrounding rock of the longwall panel. The models take into consideration the actual mining process and are developed to simulate the change in the working resistance of the shield for the same shallow burial but with different mining height conditions, ranging from 2.5 to 7 m. The results show that the average shield resistance during the basic roof initial and periodic weighting is 7 to 20 times the weight load of the mining height under the same shallow stratum conditions. By means of dimensional analysis, a relation between mining height and shield resistance in longwall panels is derived theoretically and is fitted by using the shield resistance data under different mining heights monitored in the numerical simulations. This work has led to a new method for the selection of shield support in shallow coal seams. [ABSTRACT FROM AUTHOR]

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Ionic rare earth ore is a type of featured rare earth ore in China. Its mining process suffers from a long leaching cycle and considerable consumption of leaching agents. Improving mining efficiency requires a sound physical understanding of the leaching process. In this study, the CFD-based numerical model is used to analyze the physical process of leaching through porous media formed by particles. The simulation results indicate that a lower packing porosity and smaller particles packed granular porous medium result in much larger energy dissipation during seepage, and the energy dissipation increases with seepage velocity. It is found that when the seepage velocity increases to a certain high value, the energy dissipation exceeds the value predicted by Darcy's law, which is mainly caused by liquid turbulence. Additionally, the effect of particle shape is examined. The results show that the granular medium composed of prolate particles causes larger energy dissipation than oblate particles, and spherical particles play the least role. This phenomenon may result from the particle shape affecting the area of the frontal contact surface between particles and liquid. The results provide new insights into the fundamental understanding of percolation and seepage behaviors in the ion-adsorption-type rare earth ore leaching process. [ABSTRACT FROM AUTHOR]

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

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

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

Tunnel failure caused due to geologic heterogeneity and variability in both mining processes and tunnel arrangement in deep metal mines is very complex. In this paper, a quantitative risk assessment for deep tunnel failure was conducted using clustering and logistic regression. The study was performed by considering various representative evaluation indexes of geological conditions, mining disturbance, and microseismic (MS) data. Comprehensive Seismic Event Clustering (CSEC) methodology was used to analyse the MS data to filter noise data and identify seismic sources. Additionally, peak particle velocity (PPV) was used to quantitatively evaluate the influence of MS activities on the response of tunnel which would aid in determining the PPV distribution characteristics of a large regional tunnel. Furthermore, Excavation Vulnerability Potential (EVP) index was used to quantitatively evaluate the effect of site conditions on response of the tunnel. Thus, based on logistic regression, PPV and EVP were used to establish a risk assessment model to determine the tunnel damage levels and probability of damage occurrence. The successful application of the proposed method at the Ashele copper mine demonstrates that it is capable of conducting a risk assessment for tunnel failure in deep metal mines. [ABSTRACT FROM AUTHOR]

With the increasing improvement of national ecological standards, the eco-environmental problems caused by super thick coal seam mining in western China are becoming more and more serious. The failure law of weak overburden stratum is an important factor affecting the safe mining of coal. The failure characteristics of weakly cemented overburden under high-intensity mining in the mining area of western China were studied. For this purpose, a case study was conducted in the 1101 working face of the Baituyao Coal Mine in Ürümqi County. Based on the analysis of geological conditions in the study area, we combined empirical calculations with engineering analogy, physical simulation, and numerical simulation to comprehensively analyze the characteristics of mining-induced overburden failure. The study showed that the overburden in the study area had several unfavorable engineering geological characteristics, including ease of softening in the presence of water. The Middle Jurassic Xishanyao Formation is a directly recharged aquifer with a weak water-retaining property. Overburden failure mainly occurred at the two ends of the open-off cut. During the mining process, vertical fissures and bed-separated fissures were periodically developed and closed, and the fissures were interconnected. The overburden was fractured, and the fractured zone showed a trapezoidal shape, tapering off from bottom to top. The heights of the caving zone and the water-conducting fracture zone were 25 and 280 m, respectively, in the 1101 working face of the Baituyao Coal Mine, and the ratio of fracturing to mining height was 14.0. Due to the weakly cemented overburden and the presence of the Neogene weak aquifer, the risk of water and sand bursts still exists in this working face under high-intensity mining. Our findings shed light on the safe mining and environmental protection of the ground surface in coal mine shafts in western China. [ABSTRACT FROM AUTHOR]

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

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

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

With the progress of science and technology and the gradual improvement of China s ecological environment and environmental protection system, ion-type rare earth mining technology has also been improved and improved in research and practice. Combined with the requirements of China s ecological environment protection, this paper analyzes the impact of different leaching processes and leaching agents on the ecological environment in the development process of ion-type rare earth. The ecological damage degree caused by different leaching methods and the impact of pollution factors brought by different leaching agents on the environment were discussed. Finally, the ecological environment prevention measures in ion-type rare earth mining were expounded, providing a reference for the ecological environment protection in the ion-type rare earth mining process. [ABSTRACT FROM AUTHOR]

Most of the coal mines in Southwest China are located in mountainous areas with high vegetation coverage, and most activities are carried out under the mountains. The deformation monitoring and mechanical behavior analysis of the mining area helps reveal the typical mountain deformation and failure mechanism caused by underground mining activities and reduce the risk of mountain collapse in the mining area. In this manuscript, a research method for mountain stability in mining areas is proposed, which combines InSAR deformation monitoring with numerical analysis. Based on the high-precision deformation information obtained by DS-InSAR and the landslide range, a three-dimensional explicit finite difference numerical analysis method was used to reconstruct the landslide model. According to the layout of the coal mining working face, the variation mechanism of overlying stratum stress and the mountain slip in the coal mining process is inverted, and the mechanism of mountain failure and instability in the mining area is analysed. Based on the sentinel data, the experiment performed time series monitoring and inversion analysis of the mountain collapse in Nayong, Guizhou, China. The results show that mining activities a certain distance from the mountain will affect mountain stability, and there are specific mechanisms. From 2015 to 2017, the stress redistribution of overlying strata above the goaf area resulted in dense longitudinal cracks in the landslide body due to coal mining. The mountain is in a continuous damage state, and the supporting force to prevent collapse continues to decrease, resulting in a gradual decrease in landslide stability. Both the time series DS-InSAR monitoring results and numerical simulation results verify the actual occurrence and development of the on-site subsidence. [ABSTRACT FROM AUTHOR]

To find out the characteristics of geological structure exposed in the mining process of 12,318 working face in Pansan Mine and grasp its influence law on subsequent coal seams mining, the structure was first determined as the collapse column by means of 3D seismic, transient electromagnetic detection, SYT detection and other methods, and its development characteristics, conductivity and water enrichment were identified. FLAC3D numerical simulation software was used to analyze the characteristics of vertical stress and plastic failure zone in different coal seams during mining. Finally, by comparing the ultimate failure depth of floor and the thickness of waterproof layer in the process of each coal seam directly pushing through the collapse column, the risk of water inrush and the prevention are analyzed. The results show that the exposed geological structure is characterized by weak water-rich collapse column. Under the influence of the mining of the previous coal seam and the activation of the collapse column, the subsequent coal seam is in the low-stress area before mining, which increases the floor failure and causes the activation of the collapse column more easily during mining. [ABSTRACT FROM AUTHOR]

In order to prevent the occurrence of water inrush accidents, it is particularly important to predict the mine water inrush, especially the accurate prediction of the mine water inflow in the coal mining process. Mine water inflow is caused by mining disturbance, groundwater flows into mining panels along the mining-induced fissures, and a depression cone of water table is formed in certain range around the mining sites. Mining panel is usually regarded as an irregular "virtual large diameter well" so as to calculate mine water inflow in China. However, in the mining process, the area, shape, and cross section of goafs are constantly changing, so is the water inflow. Therefore, the central position and influence radius of the "virtual large diameter well" in the spatial and temporal distribution are in a dynamic process of continuous movement and expansion, rather than being confined to a static position. This paper firstly analyzes the formation mechanism of coal mine roof water inflow and the errors and defects in the calculation of mine water inflow by virtual large diameter well (VLDWM). Then, based on the theory of steady flow and combined with the dynamic change process of goaf area and depression cone of water table during mining activities, this paper proposes an improved method and puts forward a concept of dynamic virtual large diameter well (DVLDWM) and establishes a theoretical model of the central position and influence radius of the "mining large diameter well" moving forward. The first (periodic) caving step is taken as the calculation unit and generalized as the "dynamic large diameter well," which is used to calculate the dynamic water inflow in the process of mine advancing. Taking the No.7208 mining panel in Zhangshuanglou Coalmine in Xuzhou City, Jiangsu Province, as the study area, the mine water inflow was calculated dynamically by using the DVLDWM. The results show that the mine water inflow calculated is similar to the actual mine water inflow of the No.7208 mining panel observed, thus proving the reliability and credibility of the DVLDWM. [ABSTRACT FROM AUTHOR]

Striking a balance between high-intensity coal mining and environmental protection has been a challenge in the Yushen mining area, which is an important coal production base in China located in an arid and semi-arid ecologically fragile environment. The 122,109 working face of the Caojiatan coal mine was used as a model to coordinate coal production with ecological protection. Theoretical analysis and field monitoring revealed that the maximum surface subsidence was 5.6 m, and the development height of the diversion fracture zone was 21 times the coal seam thickness. The influence of mining process parameters and mining methods on surface ecological damage and water loss was further analyzed using the fluid–solid coupling method. The results showed that exclusive pursuit of high-intensity mining would induce irreversible disasters including aquifer water loss and cultivated land damage; the degree of influence was directly proportional to the working face length, mining height, and mining method. Proper adjustments of these parameters could help realize water-controlled coal mining. The results provide an empirical basis for allowing both exploitation of coal resources and protection of the environment in ecologically fragile areas. [ABSTRACT FROM AUTHOR]

The static and dynamic inflow of water from the roof aquifer changes as mining progresses. We used a second-order dynamic model to describe the water inflow process. The parameters of the water inflow model were solved using actual drainage from roof aquifers at nine working faces in the Yuanyanghu mining area of the Ningxia Autonomous Region, China, as well as the peak water inflow values, their locations, the equilibrium values of water inflow, and their initial occurrence locations. The parameters of the second-order dynamic model of water inflow were inversely calculated. The peak values of water inflow without drainage were also calculated. The results indicate that pre-drainage of roof water significantly weakens the intensity of water inflow during the mining process, reducing peak values by more than 72%. The characteristics of the water-conducting fractured zones determine the major drainage locations, while the water-rich and water-conductive nature of the direct discharge aquifer affects the water inflow equilibrium values and initial occurrence positions. The results show that the model parameters and characteristic values of water inflow are determined by the hydrogeological nature of the roof strata, water-conducting fractured zone(s), and mining speed. [ABSTRACT FROM AUTHOR]

Mine roof water (water in the overlying aquifers of coal seam) seriously threatens the safe production of coal mines in the Ordos Basin in China. Transient electromagnetic (TEM) and seismic methods are the two key methods of mine roof water detection. To exploit the advantage of each method, the seismic-constrained TEM method is proposed. First, the seismic-constrained TEM inversion algorithm was constructed by adding a cross-gradient function to the pseudo-2D TEM inversion algorithm. The cross-gradient function makes the structures of the TEM and seismic models consistent in inversion. To match the seismic and TEM model grids, the interpolation of the seismic impedance model was proposed. Then, the proposed algorithm was successfully used in the Maiduoshan coal mine in the Ordos Basin. Data acquisition, seismic-constrained TEM inversion and interpretation were carried out. Seventeen boreholes were drilled to verify the interpretation results, and the drilling results are consistent with the detection results. Finally, the seismic-constrained and single TEM methods were compared. Results show that the seismic-constrained TEM method is superior to the single TEM method. The structural consistency of the resistivity and seismic impedance models increases in the seismic-constrained TEM inversion and decreases in the single TEM inversion. Seismic-constrained TEM inversion can add the stratigraphic structure information provided by the seismic method to the TEM inversion, thereby improving the inversion results. [ABSTRACT FROM AUTHOR]

Vegetation recovery is an important marker of ecosystem health in the mining area. Clarifying the influence of vegetation recovery on the characteristics of soil microbial community and its assembly process can improve our understanding of the ecological resilience and self-maintaining mechanism in the open-pit mining area. For this purpose, we employed MiSeq high-throughput sequencing coupled with null model analysis to determine the composition, molecular ecological network characteristics, key bacterial and fungal clusters, and the assembly mechanism of the soil microbial communities in shrubs (BL), coniferous forest (CF), broadleaved forests (BF), mixed forest (MF), and the control plot (CK, the poplar plantation nearby that had been continuously grown for over 30 a without disturbance). The results showed that the vegetation restoration model had a significant influence on the a-diversity of the microbial community (p < 0.05). Compared with CK, Sobs and Shannon index of MF and CF have increased by 35.29, 3.50, and 25.18%, 1.05%, respectively, whereas there was no significant difference in the a-diversity of fungal community among different vegetation restoration types, Actinobacteria, Chloroflexi, Proteobacteria, and Acidobacteria were the dominant phyla. The diversity of the first two phyla was significantly higher than those of CK. However, the diversity of the last two phyla was dramatically lower than those of CK (p < 0.05). Ascomycota and Basidiomycota were dominant phyla in the fungal community. The abundance and diversity of Ascomycota were significantly higher than those of CK, while the abundance and diversity of the latter were considerably lower than those of CK (p < 0.05). The stochastic process governed the assembly of the soil microbial community, and the contribution rate to the bacterial community construction of CK, CF, BF, and MF was 100.0%. Except for MF, where the soil fungal community assembly was governed by the deterministic process, all other fungal communities were governed by the stochastic process. Proteobacteria and Acidobacteria are key taxa of the bacterial network, while Mortierellales, Thelebolales, Chaetothyriales, and Hypocreales are the key taxa of the fungal network. All these results might provide the theoretical foundation for restoring the fragile ecosystem in the global mining region. [ABSTRACT FROM AUTHOR]

Wasteless mining has become the mainstream mode of China's mining industry, which is an environmentally friendly and sustainable mining method. To effectively evaluate the construction of a green mine, the wasteless mining evaluation method was proposed, based on the intuitionistic fuzzy set theory and the Vise Kriterijumska Optimizacija I Kompromisno Resenje (VIKOR) decision-making method in this study. Firstly, the intuitionistic fuzzy sets for six indicators (such as waste rock utilization, tailing sand utilization and the current mining situation) of the Dongguashan Copper Mine were established, based on the intuitionistic fuzzy set theory and the national standard system. Secondly, referring to the green mine evaluation system, the index weights were calculated with the Analytic Hierarchy Process (AHP) method. Finally, the above intuitionistic fuzzy set matrix was ranked by the VIKOR method. The calculation results show that the group utility value of this mine is 0.1943 ∈ (0,0.2), which is at level I; the individual regret value is 0.0916 ∈ (0.075,0.15), which is at level II; the compromise value is 0.2193 ∈ (0.2,0.4), which is at level II. Through comprehensive assessment, the final evaluation of the wasteless mining in the Dongguashan Copper Mine is Grade II. The Dongguashan Copper Mine is one of the first mining enterprises subject to the transformation into wasteless mining in China. The results of the final evaluation are consistent with the current status of wasteless mining in the Dongguashan Copper Mine. [ABSTRACT FROM AUTHOR]

The mining areas in Western China are characterized by water shortage and ecological fragility, and the coal resources in these areas are extracted in a large-scale and highly intensive manner, which is highly likely to induce ecological problems, such as soil erosion and grassland degradation. In addition, there is a secondary protection zone of Hongshixia water source near Guojiatan minefield. If the water resources loss of Salawusu Formation is too large, it will affect the normal water supply of Yulin city. To reasonably coordinate coal exploitation and water protection, the development characteristics of water-conducted fissures with different backfill ratios are obtained in combination with theoretical analysis, field test, and numerical modelling. The panel layout of the layered-backfill-based water protection working face and the parallel operation of mining and backfilling are designed, and a feedback regulation system integrating hydrological monitoring and backfill ratios is established, which assists in evaluating the effectiveness of water protection. The results indicated that when the slicing mining method was adopted with the roof naturally caving, the maximum development height of the water conducted fracture zone was 220.0 m (developed to the Yan'an Formation), and the water conducted fracture zone could only develop to the Yan'an Formation without crossing the Zhiluo Formation when the backfill ratio reached 80%. The water emission rates in the west of the field testing area reduced from 334.95 m3/h to 60.60 m3/h, dropping by 86.86%. Compared to the scene prior to the layered backfill mining, the shallow water outflow was reduced by 72.74 m3/h, and it helped annually reduce the shallow water loss of 637200 m3, which was equivalent to 1.74% of the actual water supply to Yunli city every year. The results of this study can provide guidance on effectively avoiding the loss of shallow water resources that are regarded as indispensable sources of domestic water. [ABSTRACT FROM AUTHOR]

To investigate the temporal and spatial evolution process of overlying karst mountain instability caused by mining, the case of "8.28" mega landslide in Pusa, Nayong County, Guizhou Province, China, is taken as the example. Based on the results of the field investigation after the disaster, the complete process of rock strata fracture and slope instability under the descending and ascending mining conditions of gently inclined coal seam is reproduced by similitude model experiments. According to the key motion features of overburden deformation and fracture evolution law, the failure process of slope collapse controlled by deep and large karst fissures under mining action is summarized. And the change law of overburden pressure and displacement in the mining process is analyzed as well as the failure mode of slope collapse is proposed. The results show that the slope experiences four failure stages in the process of coal seam descending mining: coal seam roof caving, overburden cantilever tension fracture, overburden integral dumping subsidence and slope instability collapse, and the slope undergoes deformation toward the free surface and downward. During the ascending mining process, the slope experiences four failure stages: periodic caving of coal seam roof, upward transmission of separated fractures, overburden integral bending subsidence and slope instability collapse, and the slope undergoes deformation toward the inside of the slope and downward. The rock mass ahead of the advancing direction of working face has the phenomenon of tension–compression stress transformation. Along the mining direction, the overburden sequentially experiences the change process of pressure increase, decrease, or increase again, and stabilization. Deep and large karst fissures at the slope top are the structural basis for the occurrence of collapse. Coal mining activities have a certain promoting effect on mountain cracking and rock fragmentation. The failure mode of slope can be summarized as tension–shear–slip–toppling collapse failure. Improved understanding of the deformation movement characteristics and damage mode of slope can aid in early identification and timely warning of geo-hazards in karst area. Highlights: This paper focuses on the deformation movement features and failure modes of mountains controlled by deep and large karst fissures under mining action. The full process of rock strata fracture and slope instability under descending and ascending mining conditions is reproduced in a simulated model. Extensive karst fissures at the slope top are the main structural basis for the occurrence of collapse. Coal mining activities have a certain promoting effect on mountain cracking and rock fragmentation. The failure mode of slopes can be summarized as tension-shear-slip-toppling collapse failure. [ABSTRACT FROM AUTHOR]

Assessing the stability characteristics of high rock slope under rainfall via theoretical research, numerical simulation, and field monitoring is of great implications for safety construction in open-pit mine engineering. Thus, based on the Hoke-Brown criterion, instantaneous internal friction angle and cohesion of high-slope rock mass under high stress conditions were deduced, and a nonlinear strength reduction method for high rock slope was established. The safety factors of the open-pit mine were calculated by COMSOL Multiphysics, which considering the high rock southwest slope and detected rainfall in Dagushan Open-pit Mine, China. The results showed that high rock slope stability could be more accurately analyzed by the proposed method due to its full consideration of slope stress state effect compared with the equivalent Mohr- Coulomb method. When the slope is low, the difference between the calculation results of the equivalent Mohr- Coulomb method and the proposed method is small, but with the increase of the slope height, the difference between the two calculation results gradually increases. When the transient saturated is formed in the slope surface layer and gradually increases, the reduction rate of the factor of safety (FOS) gradually increases. When the total rainfall is the same, the effect of short-term heavy rainfall on slope stability is less than that of long-term ordinary rainfall. The results obtained form this work provided important insights into the stability of high rock slope and rainfall infiltration in open-pit mine, and the safety factor is crucial for guiding the mining process design. [ABSTRACT FROM AUTHOR]

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

Coal will continue to play an important role in China's economic development and social development in the coming decades. However, due to the complex distribution conditions of coal resources, the mining of coal resources is subject to various restrictions. Coal and gas outburst is an important issue in coal mining, and the threat to the mining of coal resources caused by high gas outburst activity has been receiving more attention. In order to solve the problems related to safe and efficient mining under coal seams with gas outburst, such as mining difficulties, large amounts of work, resource waste, no guaranteed gas treatment time, and low economic efficiency, it is necessary to innovate mining technology and methods for managing gas outburst in coal seams to improve the efficiency of coal mines and to solve the above problems. This study proposes a green mining technical method system known as the "L-H method", which is applicable to the safe and efficient mining of coal seams with gas outburst based on combined theoretical analysis and numerical simulation. The following research results are achieved: (1) The "L-H method" is proposed, and a mining area model of coal seams with gas outburst is established. The specific details of the method and the implementation process are introduced. (2) Examples of H coal mine applications are presented, and the effects of the implementation of the "L-H method" are analyzed and summarized through mine pressure observations from roadways, and it is concluded that the implementation of top-cutting and pressure-relief technology has a good control effect on the roadway-surrounding rock and that gas extraction reaches the national standard of less than 8 m3/t for protrusion prevention; this ensures safety and also achieves efficient mining. This study will provide a good reference for the implementation of green mining methods to similar coal and gas outburst mines. [ABSTRACT FROM AUTHOR]

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

Roof-breaking characteristics and ground pressure behavior of the coalface are instrumental in guiding deep Jurassic coal seam mining, in particular in the Shaanxi and Inner Mongolia regions of China. A thick-plate mechanical model (TPMM) of the main roof was developed and applied to the case study of 21102 first-mined coalface (FMC) of the Hulusu Coal Mine (HCM) in the Hujirt Mining Area (HMA), China. A theoretical analysis performed via the developed model revealed that the first and periodic breaking intervals of the main roof were 40.6 and 25.0 m, respectively. The roof failure occurred in the tensile mode, was controlled by the internal stress σ x in the rock strata, and started from the center of the long side with the fixed support in the goaf. The field measurement of roof weighting was also performed for the coalface advance from zero to 400 m. The measurement results showed that the first weighting average interval was 41.4 m, and the average interval of periodic weighting was 22.0 m, which agreed with the theoretical calculation and proved the proposed model's feasibility. Finally, the frequency distribution features of the hydraulic support working resistance in the FMC were analyzed statistically. The results showed that the ZY10000-16/32D supports could adapt to the mining geological conditions of the FMC. However, the margin of the rated working resistance of supports was still small. Thus, roof management enhancement during the mining process was strongly recommended. These research findings could offer theoretical guidance for safe and high-efficiency production in the coal mines under similar geological conditions. [ABSTRACT FROM AUTHOR]

The deep resources within existing gold mines have great potential to prolong the life of mines such as the Jiaojia gold mine in Shandong province in China. However, with the increase of mining depth in the Jiaojia gold mine, the overburden stress is increasing and the spatial and temporal distribution of the mining stress field is becoming more complex. This in turn is causing the spatial structure of the overlying strata to be seriously damaged, which often leads to mine water disasters. In this paper, based on the analysis of borehole data and a profile map, a three-dimensional geological model was established to predict the height of the water-conducting fracture zone near a regionally significant fault. The effects of mining show that the maximum height of the water-conducting fractured zone is about 21.2 m during mining at the − 700 level. The shape of the fractures that are developed varies from nearly horizontal to micro arch-shaped. The failure range of the plastic area near the fault was found to be larger near the fault than that at a distance from the fault. The stress distribution on both sides of the fault was found to be not continuous, and to be larger in the hanging wall than that in the footwall. A stress concentration zone was found to be formed in the front and back of the stope during the mining process and to increase with mining depth. This method can restore the original state of the underground stress field to the greatest extent and make up for the lack of empirical formula theory and the limitation of the similar material methods for deep mining, which is relatively more accurate and reliable. [ABSTRACT FROM AUTHOR]

Coal mining in areas with deep confined water is very dangerous; to ensure safety, it is necessary to clarify the damage characteristics of the working face floor. To directly reflect the failure characteristics of the working face floor under the coupled effects of mining stress and confined water pressure, this study considers the mining above confined water in the deep coal seam of the II633 working face of the Hengyuan coal mine in the Huaibei mining area as the engineering background. With the use of the similar material simulation experimental method and a self-designed monitoring system for confined water diversion and a confined water loading system and a confined water lifting system that can directly reproduce the floor confined water lifting characteristics affected by floor failure during coal mining, the mining stress distribution patterns, deformation and failure characteristics of the overburden, and diversion characteristics of the confined water in the working face floor are investigated. The results show that the floor undergoes three stages of deformation in the horizontal direction: premining stress concentration-related compression (10–15 m ahead of the working face), postmining floor pressure relief-related expansion, and roof collapse-related stress recovery (the distance from the lagging working face is 15–20 m). In the vertical direction, a soft rock layer blocks the continuous transfer of mining stress to deeper layers and produces an important cushioning effect. In the process of coal mining, shear cracks easily develop in the coal wall in front of and behind the working face. After the coal seam is excavated, the length of the fractures that develop in the physical model is 27 cm. The confined water loading system can visually reproduce the hydraulic characteristics of the confined water during the mining process; that is, the confined water easily bursts at the front and back ends of the coal wall in the goaf. The error, as determined by comparison between the field measurement results and the theoretical calculation results, is only 0.617 m, verifying the reliability of the similar simulation method. [ABSTRACT FROM AUTHOR]

The increasing use of high-voltage transmission wires requires more and more high-voltage pylons, and sometimes, constructing pylons in mining areas is very urgent. To ensure the safe operation of pylons, coal pillars with large side lengths are usually used to provide sufficient support; however, this results in a huge waste of coal. Eight high-voltage pylons are arranged on the ground surface corresponding to the location of working face 1110 of Sima Coal Mine in Shanxi Province, China, which cannot be mined by traditional methods. Taking this as the engineering background, the failure mode of high-voltage pylon is first analyzed. Using FLAC3D numerical simulations, the influence of five different mining plans on ground surface deformation in working face 1110 is evaluated, and the vertical settlement and horizontal deformation in different areas of the ground surface, as well as the variation law of horizontal strain and slope are analyzed. According to the numerical simulation results, the range of thickness-limiting mining or backfill mining in working face 1110 is shown in scheme 3, and the key regions in the mining process are determined. Secondly, the strengthening scheme of high-voltage pylons is designed, that is, the four foundations of high-voltage pylons are connected as a whole with steel supports and steel connectors so as to improve the structural strength of the high-voltage pylon. Finally, the position change in the foundation of high-voltage pylons was monitored for 22 consecutive months. The results show that the maximum settlement of the high-voltage tower foundation is 3.1 m, which is consistent with the actual mining thickness; The high-voltage pylon was stably moved, and the change in transmission line tension and total length was usually less than 1.0%. The combined mining scheme and foundation strengthening scheme can ensure the safe operation of high-voltage pylons and provide a new method for the stability control of ground buildings in coal mining subsidence area. [ABSTRACT FROM AUTHOR]

Coal remains an important fuel and energy, especially in China. For coal mining in deep mines, the threat of coal and rock dynamic disasters (such as coal and gas outburst) to safe production is becoming more and more serious with the greatly increasing geo-stress and gas pressure. Hence, it is particularly important to real-timely monitor and finely identify outburst-hazardous zones and their hazard levels during coal mining. However, conventional methods fail to continuously and precisely monitor outburst-hazardous zones in spatial distribution. Previous studies have shown that under the coupling action of stress and gas, the electric potential (EP) signals can be generated and their response characteristics are closely related to the loading state and damage evolution process of coal. The inversion imaging method can be utilized to analyze the spatial distribution of the EP signals. On this basis, the field tests were conducted to study the EP response characteristics to the mining process of deep coal seams and analyze the relationship between the EP response and outburst hazard. Moreover, in view of the EP inversion imaging mechanism, the bilateral EP inversion n model was established on the mining-disturbed coal seam ahead of the mining face and the field application was also carried out. Furthermore, on account of the membership index of fuzzy mathematics, the critical EP inversion value was proposed. Then the outburst-hazardous zones in the coal seam ahead of the mining face were divided finely and identified quantitatively. In the end, the verification result showed that the yellow zones enable to identify most of outburst-hazardous zones, thus effectively avoiding the missing identification. Besides, the red zones can improve the identification efficiency, which is conducive to focusing on identifying zones with a high hazard level. The study results provide a valuable new application method for finely identifying coal and gas outburst hazards and preventing coal and rock dynamic disasters in deep coal mines. Highlights: The EP signals response can reflect the stress state and damage evolution of coal seams. The bilateral EP inversion model was established ahead of mining face to reveal the electric field distribution characteristics. The EP inversion results could identify the hazardous zones of dynamic disaster for coal and gas outburst in the coal seam. [ABSTRACT FROM AUTHOR]

Water–sand mixture inrushes into shallow underground workings have caused casualties and property loss. A coupled fluid–solid analog model was developed to simulate the water–sand mixture inrush processes during mining from fracture production and development, based on the hydrogeological conditions at the #22304 working face of the Shigetai coal mine in the Erdos coal basin of northeast China. The deformation characteristics of the overlying strata and water pressure variations within the water-flowing fractured zone were monitored and analyzed. The results show that the water–sand mixture inrush consists of three stages: development of cracks in the overlying strata, initiation of a water inrush channel, and evolution of the inrush channel. The stresses of the overlying strata, water pressures, and permeability characteristics of water and sand inrush pathways change within the three stages. These findings lay a solid foundation for predicting water–sand mixture inrushes in shallow coal mines. [ABSTRACT FROM AUTHOR]