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A special issue of Sustainability (ISSN 2071-1050). This special issue belongs to the section "Hazards and Sustainability".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 22787

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Special Issue Editors

Prof. Dr. Wei Yang

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Guest Editor

School of Safety Engineering, China University of Mining & Technology, Xuzhou 221116, China
Interests: coal-rock dynamic disaster control; digital twin technology in coal mine; fine exploration of geological structure; shale gas exploitation
Special Issues, Collections and Topics in MDPI journals

Dr. He Li

E-Mail Website
Guest Editor

School of Resources & Environment and Safety Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
Interests: coal mine gas control; coal fire prevention; high-temperature flue gas purification

Dr. Ting Liu

E-Mail Website
Guest Editor

School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China
Interests: unconventional geomechanics; flow in porous media; coal mine gas control

Special Issue Information

Dear Colleagues,

Coal is one of the most important energy resources in the world. Intelligent mining of coal resources is the direction of future development, and efficient disaster prevention and control is the prerequisite for the intelligent mining of coal. With the gradual depletion of shallow coal resources, it has become an inevitable trend to search for resources deeper underground. The special occurrence conditions of deep coal seams, such as high geostress, high ground temperature, and high gas pressure, determines that disasters occur more frequently. Common dynamic disasters encountered during underground coal mining include coal and gas outbursts, rock bursts, gas explosions, coal fires, composite dynamic disasters, etc. The efficient control of these disasters has become an important premise to ensure the safe, sustainable, stable, and green development of the coal industry. This Special Issue, titled “Advances in dynamic hazards prevention in underground mines”, aims to provide an opportunity to researchers around the globe to conduct a broader scientific and technological discussion on such advances to improve the prevention and control level of the disasters encountered during underground coal mining. The discussion topics include, but are not limited to, the basic experiments, modeling, numerical simulation studies, and field tests of dynamic coal and rock disasters; compound coal fire and gas disasters; reservoir reconstruction technology; unconventional geomechanics and gas flow in porous media, etc. Original research and review articles are welcome.

Prof. Dr. Wei Yang
Dr. He Li
Dr. Ting Liu
Guest Editors

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Keywords

coal and gas outburst
rock burst
gas explosion
compound disaster of coal fire and gas
coal mine gas development
reservoir reconstruction technology
gas flow in porous media
unconventional geomechanics
CO₂-ECBM
carbon emission reduction in coal mines

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Published Papers (12 papers)

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Research

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20 pages, 5953 KiB

Open AccessArticle

Seismic Stability Analysis of Tunnel Faces in Heterogeneous and Anisotropic Soils Using Modified Pseudodynamic Method

by Xi Chen, Kun Zhang and Wei Wang

Sustainability 2023, 15(14), 11083; https://doi.org/10.3390/su151411083 - 15 Jul 2023

Cited by 3 | Viewed by 1139

Abstract

This work assesses the seismic stability of tunnel faces advanced in heterogeneous and anisotropic soils based on the plastic limit theorem. A discretized kinematic velocity field respecting the normal flow rule is generated via a point-to-point discretization technique. The distribution of soil parameters in the depth direction including cohesion, friction angle, and unit weight are considered by four kinds of profiles. The variation in cohesion with shear direction caused by consolidation and sedimentation is considered by including an anisotropy coefficient. The seismic acceleration is represented by the modified pseudodynamic method (MPD) rather than the conventional pseudodynamic method (CPD). Based on the energy equilibrium equation, an upper-bound solution is derived. The accuracy and rationality of the proposed procedure are substantiated by comparing with the solutions obtained by conventional log-spiral mechanism and CPD. A parametric study indicates that nonlinear profiles tend to predict a smaller required face pressure than the constant and linear profiles due to the convexity of nonlinear profiles. The over-consolidated soil is more sensitive to the anisotropy coefficient than normally consolidated soil. Moreover, the adverse effect of horizontal seismic acceleration is much greater than that of vertical acceleration, and the resonance effect is more prone to happen, especially for shallow-buried tunnels. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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16 pages, 11100 KiB

Open AccessArticle

Design of Pressure Energy-Absorbing FRP Anchors and Numerical Analysis of Mechanical Properties

by Zhi Tang, Dezhi Chang, Xiaoqiao Cai, Jinguo Lyu and Hao Wu

Sustainability 2023, 15(8), 6726; https://doi.org/10.3390/su15086726 - 16 Apr 2023

Cited by 1 | Viewed by 1634

Abstract

Conventional FRP anchor rods have low elongation and poor impact resistance, both of which do not meet the support requirements of rock burst roadways. Therefore, a pressure energy-absorbing FRP anchor rod composed of an FRP rod body, tray, energy-absorbing sleeve and round table nut was designed. Numerical simulations were carried out to study the mechanical properties of the FRP anchor rod in static tension and impact tension, and to compare its mechanical properties with those of conventional FRP anchor rods. The results show that the pressure energy-absorbing FRP anchor rod is stretched in four stages: the front-elastic stage, constant resistance to compression, the back-elastic stage and damage, with an additional constant resistance to compression stage compared with conventional FRP anchors. The elongation, energy absorption and impact resistance time of the pressure energy-absorbing FRP anchor rods are greater than those of conventional FRP anchor rods, and the mechanical properties of the pressure energy-absorbing FRP anchor rods are better than those of conventional FRP anchor rods. As the impact velocity increases, the energy absorption rate of the pressure energy-absorbing FRP anchor increases non-linearly. The impact energy and impact velocity have less influence on the breaking load, elongation and energy absorption of pressure energy-absorbing FRP anchor rods. The research results can provide a theoretical basis for the application and parameter design of the pressure energy-absorbing FRP anchor rod, and provide support for the safe and efficient mining of the mine. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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11 pages, 2854 KiB

Open AccessArticle

Effect of Pressure Relief Hole Spacing on Energy Dissipation in Coal Seam at Various Mining Depths

by Hongrui Zhao, Yishan Pan, Jinguo Lyu, Yisheng Peng and Shixu Li

Sustainability 2023, 15(4), 3794; https://doi.org/10.3390/su15043794 - 19 Feb 2023

Cited by 3 | Viewed by 1818

Abstract

The large diameter pressure relief borehole is one of the most effective technical means to prevent and control rockburst during deep mining. Based on the engineering background of rockburst mines, the mechanical model of coal energy dissipation of large diameter pressure relief holes is established by theoretical analysis, and the approximate formula for calculating energy dissipation of coal is obtained. Combined with numerical simulation methods, the energy accumulation and dissipation laws of coal under various mining depths and the various spacings of pressure relief holes is studied. The results show that the upper and lower ends of the pressure relief holes have the highest degree of energy dissipation and the largest range of energy dissipation. While the energy dissipation effect on the left and right sides of the pressure relief holes is poor, a high accumulation of elastic strain energy occurs at a certain distance on the left and right sides of the relief holes. The dissipated energy of the coal seam increases continuously with the increase in mining depth and the decrease in spacing of pressure relief holes. The dissipated energy rises especially suddenly when the hole spacing changes from 1.0 m to 0.5 m. For coal seams with high rockburst risk, the spacing of pressure relief holes can be set to be less than or equal to 0.5 m, which can greatly improve the energy dissipation effect of coal seams. The studies can provide a theoretical basis for the optimization parameters of pressure relief holes for rockburst prevention. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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17 pages, 5123 KiB

Open AccessArticle

Study on the Parameters of Strengthening Soft Surrounding Rock by Electric Pulse Grouting in the Mining Face

by Xiaoguang Qiao, Runxun Zhang, Lulu Zhang, Xinghua Zhang and Xiaogang Zhang

Sustainability 2023, 15(3), 2314; https://doi.org/10.3390/su15032314 - 27 Jan 2023

Viewed by 1230

Abstract

As an effective measure for the rapid fracturing of coal and rock, electric pulse fracture technology has been successfully applied in oil extraction and natural gas discharge. Using the electric pulse fracture mechanism, this technology can be applied to grouting reinforcement to improve the infiltration efficiency of grouting. In this study, we used a numerical simulation method to establish numerical models with different electric pulse peak pressures, different grouting times and different drilling spacing conditions Through numerical simulation studies, we found that the influence range of grouting reinforcement grows with the increased maximum pressure generated by the electrical pulse. The most economical and reasonable electric pulse parameter setting is 5 MPa for static grouting pressure and 100 MPa for peak electric pulse pressure. The best grouting time to keep pressure in the borehole is determined as 9 h, and the best borehole interval is 10 m. In addition, through the treatment of the soft roof of the Caojiashan coal mine, we also found that the reinforcement sample within the grouting reinforcement range had a compressive strength of more than 1.1 MPa; after each grouting reinforcement was completed, the hydraulic bracket could advance 12 m each time, which shows that the electric pulse grouting reinforcement technology has an obvious effect on the treatment of soft roof slab. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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19 pages, 8030 KiB

Open AccessArticle

Case Study on Dynamic Identification of Overburden Fracture and Strong Mine Pressure Mechanism of Isolated Working Face Based on Microseismic Clustering

by Yiqi Chen, Changyou Liu, Jinrong Liu, Peiju Yang and Shuo Lu

Sustainability 2023, 15(1), 436; https://doi.org/10.3390/su15010436 - 27 Dec 2022

Cited by 4 | Viewed by 1664

Abstract

Strong mine pressure has a great impact upon the safety production of coal mines. Microseismic information provides a more advanced technical means for overburden fracture dynamic identification and mine pressure mechanism research, since it contains rich information on rock fracture sources. In this study, the isolated LW8102 working face in Tongxin Mine was investigated in order to propose a spatio-temporal microseismic event data analysis method based on the k-means clustering algorithm. This algorithm can handle dynamic identification of overburden fractures constrained by spatiotemporally discrete distributions of microseismic events. This provided the dynamic extension process and the fracture distribution pattern of the overburden: eight fracture extensions were formed in the overburden. In each extension, vertical fractures connected the low and high rock layers in the LW8102 and LW8103 goafs, and through fractures connected the LW8102 and LW8103 goafs in their high, middle, and low levels. Some extensions had fractures that were connected to form a closed loop structure. In the vertical fracture, there was a tendency for one or two layers of the stratum to fail first, and then extend to one or both sides. The process of through and vertical fracture propagation followed a certain temporal sequence, reflected primarily in two forms: firstly, as the vertical fracture extended to a certain layer, it provided the initial rupture space for through fracture spreading; secondly, the through fracture first broke, and then extended to the vertical fracture until it intersected with the vertical fracture or provided the initial rupture space for the expansion of the vertical fracture. By matching the overburden fracture to the mine pressure that responded to the support resistance, we analyzed the mechanism of mine pressure at the working face. Through fracture at the high level was found to be the primary cause of the occurrence of mining pressure. It was precisely placed that the formation of multiple adjacent high through fractures 110 m from the floor, triggering simultaneous instability motion of the lower multi-layer level rock; this was the main reason for the phenomenon of strong mine pressure at the working face. Meanwhile, high through fracture at 80 m from the floor was the main reason for the phenomenon of large mine pressure at the working face. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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15 pages, 6581 KiB

Open AccessArticle

Numerical Simulation of CO₂-ECBM Based on Multi-Physical Field Coupling Model

by Ziwen Li, Hongjin Yu and Yansong Bai

Sustainability 2022, 14(18), 11789; https://doi.org/10.3390/su141811789 - 19 Sep 2022

Cited by 16 | Viewed by 2478

Abstract

In this paper, heat injection and CO₂ injection are combined, and the influence of coal seam parameters on CO₂-ECBM is analyzed to improve the production of CH₄ and CO₂ reserves and the effective control of both greenhouse gases. A multi-physical field coupling model of CO₂-ECBM was established based on Darcy’s law, Fick’s law of diffusion, the extended Langmuir model for adsorption, and the equation of state. Numerical simulation of CO₂-ECBM under different coal seam parameters was carried out by COMSOL Multiphysics. The results show that increasing the injection pressure of the CO₂ injection well and the initial pressure of the coal seam can effectively increase the gas pressure and concentration gradient, which has a positive effect on improving the extraction concentration of CH₄ and the sequestration concentration of CO₂ in the coal seam. The increase of the initial temperature of the coal seam will promote the desorption and diffusion of the binary elemental gas, resulting in a decrease in the concentration of coalbed methane and a decrease in the displacement effect. In the process of displacement, the greater the initial permeability, the greater the fracture opening of the coal seam, which is more conducive to the seepage transport of the gas. The closer to the position of the injection well, the better the displacement effect and the lower the permeability rate ratio. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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16 pages, 3559 KiB

Open AccessArticle

Research on Overburden Failure Characteristics Based on the Theory of Plates and Shells

by Hongyan Qin, Jingui Zhang, Zhiheng Cheng, Zhenhua Ouyang, Liang Chen, Haiyang Yi, Xidong Zhao, Yang Li and Hao Liu

Sustainability 2022, 14(18), 11441; https://doi.org/10.3390/su141811441 - 13 Sep 2022

Cited by 1 | Viewed by 1277

Abstract

To reveal the overburden failure characteristics during backfill mining, theoretical analysis based on the theory of plates and shells and field measurements were combined. Based on the theory of plates and shells, a mechanical model for the overburden failure mechanism during backfill mining was established, through which the fracture conditions of overburden during backfill mining were judged. By analyzing the fracture process and revealing the fracture mechanism, the fractured zone in overburden during backfill mining was found not to develop uniformly, but changed in a leaping manner. Field measurement was conducted taking the 1327 working face in Xima Coal Mine (Shenyang City, Liaoning Province, China) as an example to monitor and analyze the roof-to-floor convergence (RFC), strata behaviors at the working face, and overburden failure during backfill mining. Monitoring results show that the distance between the monitoring points and the working face was highly consistent with the periodic weighting interval when the RFC increased in a leaping manner; the RFC grew in a leaping manner after each roof weighting, as well as the fractured zone. By monitoring and analyzing overburden failure, it was determined that the maximum height of the fractured zone was 10.7 m and a leaping phenomenon was present in the development process of the fractured zone. The conclusions of theoretical analysis were completely consistent with those of the field measurements, thus confirming the leaping development of the fractured zone in overburden during backfill mining. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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23 pages, 17869 KiB

Open AccessArticle

Permeability-Enhancing Technology through Liquid CO₂ Fracturing and Its Application

by Zebiao Jiang, Xiping Quan, Shixiang Tian, Hao Liu, Yaling Guo, Xiangxiang Fu and Xifa Yang

Sustainability 2022, 14(16), 10438; https://doi.org/10.3390/su141610438 - 22 Aug 2022

Cited by 4 | Viewed by 2184

Abstract

Liquid carbon dioxide (CO₂) phase change fracturing (LCPCF) is an innovative technique to improve the efficiency of gas drainage from low-permeability coal seams of high gas content. However, fracture sprouting, extension and displacement changes of coal under LCPCF need further study, and corresponding field tests are also lacking. Therefore, a mechanical model based on the thermodynamic theory of CO₂ phase change is developed in this paper. Then, the pressure change characteristics, crack propagation and displacement change of coal subjected to LCPCF were analyzed through numerical simulation. In addition, the permeability-enhancing effect of the field LCPCF test was analyzed. The results obtained from the numerical simulation show that during the LCPCF process, the crack-generation process changes with pressure as follows: microfracture–numerous microfractures–major macrofracture–macrofractures. During the development of fractures, the stress is incompletely symmetrically distributed in coal centered on the fracturing borehole. The failure occurs stochastically in the coal in the vicinity of the fracturing borehole at first, and then it gradually propagates to the inner seam of coal as the gas pressure increases. The following result can be obtained from field experiments: the permeability coefficient of coal seams after increasing the permeability through LCPCF is 2.60~3.97 times that of coal seams without presplitting. The average concentration of gas extracted in coal seams within the zone having undergone an increase in permeability through liquid CO₂ fracturing is 2.14 times greater than that within the zone without presplitting. The average pure amount of gas extracted within the zone having undergone an increase in permeability through LCPCF is 3.78 times greater than that within the zone without presplitting. By comparing coal seams before and after fracturing in the field test, it can be seen that the LCPCF presents a favorable effect in increasing the permeability of low-permeability coal seams. This provides an effective approach for increasing the permeability of coal seams in coal mines with similar geological conditions. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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26 pages, 14222 KiB

Open AccessArticle

Remote Sensing for Surface Coal Mining and Reclamation Monitoring in the Central Salt Range, Punjab, Pakistan

by Nafees Ali, Xiaodong Fu, Umar Ashraf, Jian Chen, Hung Vo Thanh, Aqsa Anees, Muhammad Shahid Riaz, Misbah Fida, Muhammad Afaq Hussain, Sadam Hussain, Wakeel Hussain and Awais Ahmed

Sustainability 2022, 14(16), 9835; https://doi.org/10.3390/su14169835 - 9 Aug 2022

Cited by 10 | Viewed by 3399

Abstract

The expansion and exploitation of mining resources are essential for social and economic growth. Remote sensing provides vital tools for surface-mining monitoring operations as well as for reclamation efforts in the central Salt Range of the Indus River Basin, Pakistan. This research demonstrates the applicability of remote sensing techniques to the coal mining monitoring scheme to allow for effective and efficient monitoring and to offset the adverse consequences of coal mining activities. Landsat 8 OLI images from June 2019 and 2020, and a Landsat 7 ETM+ image from June 2002, were used for this study. A three-phase methodology including Normalized Difference Vegetation Index (NDVI) analysis, land cover mapping, and change detection approaches was adopted. Image classification based on Tasseled Cap Transformation and the brightness temperature At-satellite using the K-means algorithm was implemented in a GIS program to identify seven land cover classes within the study area. The results show some level of surface disturbance to the landscape due to the coal mining reclamation activities that had taken place over the 18-year time period. From 2019 to 2020, about 3.622 km² of coal mines or barren land were converted into bare agricultural land. Over the years, it was also observed that reclamation areas exhibited higher values of NDVI than coal mining areas. The mean NDVI for coal mining areas was 0.252 km², and for areas of reclamation, it was 0.292 km² in 2020, while in 2019, the value for coal mining sites was 0.133 km², and 0.163 km² for reclamation sites. This trend suggests that coal-mining operations can be monitored using satellite data, and the progress of reclamation efforts can be assessed using satellite NDVI data from the target locations. This study is beneficial to agencies responsible for monitoring land cover changes in a coal mine because it provides a cost-effective, efficient, and robust scientific tool for making mine site allocation decisions and for monitoring the progress of reclamation efforts. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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13 pages, 4416 KiB

Open AccessArticle

Internal Temperature Variation on Spontaneous Combustion of Coal Gangue Dumps under the Action of a Heat Pipe: Case Study on Yinying Coal Mine in China

by Na Zhao, Yongbo Zhang, Xuehua Zhao, Jinrong Niu, Hong Shi, Na Yang, Tong Gao and Lina Guo

Sustainability 2022, 14(16), 9807; https://doi.org/10.3390/su14169807 - 9 Aug 2022

Cited by 3 | Viewed by 1430

Abstract

Coal gangue spontaneous combustion is a serious catastrophe associated with mining activities. Generally, the areas of coal gangue spontaneous combustion are regions of tremendous heat accumulation. Mastering the regularity of deep temperature distribution and eliminating internal heat is an effective method to control spontaneous combustion. In this study, using self-developed heat pipe (HP) and intelligent cloud monitoring software, three sets of single pipe experiments were conducted in different temperature areas of the coal gangue dump in Yinying Coal Mine. A fitted model between shallow and deep temperatures was established using the least squares method to perform goodness-of-fit tests and significance analysis, and to analyze the internal temperature variation under the action of an HP. The results show that the quadratic model fits better and the regression is significant, and can be used as an empirical regression formula for the shallow temperature estimation of the deep temperature. The temperature was clearly suppressed by the HP, and the average cooling range reaches 21.44% within 700 h. However, the temperature of the control group without an HP continued to rise by 8%. In the three experimental groups, the effective control radius of the single HP was 3 m. The best cooling was achieved when the gangue depth was 1 to 4 m and the temperature was between 90 °C and 450 °C. The study shows that the HP has a great effect on thermal removal and inhibits spontaneous combustion of the gangue. In addition, this paper also provides a theoretical basis for the technology of HP treatment of spontaneous combustion gangue dumps. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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19 pages, 8459 KiB

Open AccessArticle

Study on the Characteristics of Water Jet Breaking Coal Rock in a Drilling Hole

by Yabin Gao, Peizhuang Han, Fei Wang, Jing Cao and Shaoqi Zhang

Sustainability 2022, 14(14), 8258; https://doi.org/10.3390/su14148258 - 6 Jul 2022

Cited by 6 | Viewed by 1490

Abstract

Water jet technology is an effective measure by which to improve the efficiency of deep coalbed methane mining. Nevertheless, the effect of a water jet impinging on coal rock remains unclear. In this study, numerical simulation is used to analyze a water jet impingement drill test block, after which experimental verification is carried out. Next, on the basis of the experimental verification that the simulation method is feasible, the influence factors of the water jet impingement in the drill hole are analyzed. It is concluded that the phase-field variables based on the fracture change method can effectively characterize the damage and destruction of coal rock. The water jet impact in the borehole has a central damage failure zone and two-side damage failure zone, and the damage failure ratio n is used to characterize the degree of damage to the coal rock. When the jet target distance is 70 mm, the damage ratio n is closest to 1, and the effect of water jet impact on coal-rock is the best. When the wall roughness is less than 10 mm, the blocking effect on the jet is dominant, resulting in a negative correlation between the damage size and the roughness. When the wall roughness exceeds 10 mm, the development of cracks and the connection effect exceed the blocking effect, resulting in larger damage. Therefore, it can be seen that the effect of a water jet impacting on coal rock is positively related to jet pressure. When the jet target distance is 70 mm, the damage range of 30 MPa jet pressure to the center and both sides of the coal rock reaches about 1.1 m, thus signifying a good coal rock breaking effect. The wall roughness has a significant effect on the coal rock breaking effect of the water jet. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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Review

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15 pages, 3941 KiB

Open AccessReview

Research Progress on Stress–Fracture–Seepage Characteristics for Hazard Prevention in Mine Goafs: A Review

by Xuanping Gong, Sheng Xue, Baiqing Han, Chunshan Zheng, Licheng Zhu, Yangyang Dong and Yaobin Li

Sustainability 2022, 14(19), 12107; https://doi.org/10.3390/su141912107 - 25 Sep 2022

Cited by 1 | Viewed by 1558

Abstract

Large-scale coal mining has created many goaf areas, which have become one of the most frequent sources of mine hazards. Investigations on the stress–fracture–seepage characteristics around goafs could help with identifying and controlling goaf-area hazards. Scholars have conducted theoretical analyses, similar simulation experiments, numerical simulations, and field measurements to analyze the multifield coupling development of mining stopes, including the stress variations, fracture advancement, and permeability-change characteristics. In the longwall-mining process, a stress-relief zone is formed above the goaf area, while a stress-concentration zone is formed in the adjacent coal seams. Mining-stope fracture goes through a process of stress-relief expansion, stress-recovery closure, and end-fracture expansion. The permeability of coal rock in mining stopes rises in all directions with the increase in the fracturing ratio. Further studies could concentrate on the distribution characteristics of the abutment pressure around the goaf area. A permeability model based on the coupling of the coal stress, damage, gas adsorption, and desorption is expected to be established to improve the accuracy of the permeability prediction and seepage analysis at the boundary of the goaf area. Relevant studies could provide better theoretical guidance for preventing hazards, such as gas-related incidents and coal spontaneous combustion in the goaf, as well as for the stability control of the goaf boundary. Full article

(This article belongs to the Special Issue Advances in Dynamic Hazards Prevention in Underground Mines)

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