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Processes
Special Issues
Monitoring, Process Control, Simulation, and Optimization in Coal Mining
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Monitoring, Process Control, Simulation, and Optimization in Coal Mining

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Process Control and Monitoring".

Deadline for manuscript submissions: 31 March 2025 | Viewed by 3282

Special Issue Editors

Dr. Yangyang Guo

E-Mail Website
Guest Editor
State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China
Interests: mine safety; gas flow theory in coal; dynamic disasters in coal mines
Dr. Bo Li

E-Mail Website
Guest Editor
State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454000, China
Interests: coal mine disaster prevention and control; occupational health
Special Issues, Collections and Topics in MDPI journals
Dr. Wei Zhao

E-Mail Website
Guest Editor
School of Emergency Management and Safety Engineering, China University of Mining & Technology (Beijing), Beijing 100083, China
Interests: coal mining safety; gas diffusion; ECBM; emergency management and science
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Coal plays an important role in the world economy and industrial development. Shallow coal resources have been gradually exhausted, and coal mining has entered the stage of deep mining. In this environment, the geological conditions are more complex, with high temperatures, high ground stress, high gas pressure and low permeability, which pose a threat to the safety of workers mining coal. Problems such as coal and gas outburst, rock burst pressure and gas dust explosion are more likely to occur in the deep mining stage. It is thus of great significance to study the underlying mechanisms of coal mine disasters and how to prevent them for the safe and efficient mining of coal resources.

This Special Issue solicits original research articles and review papers reflecting the advances in research concerning process safety in coal mining. Topics of interest include, but are not limited to:

  • Mechanisms and preventions of dynamic disasters;
  • Prevention of coal mine gas and fire coupling disasters;
  • Gas extraction technology of low permeability coal seams;
  • Coal mine gas explosions;
  • Coal bed gas adsorption and desorption and diffusion.

Dr. Yangyang Guo
Dr. Bo Li
Dr. Wei Zhao
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • mechanisms and preventions
  • coal seams
  • gas extraction technology
  • coal bed gas adsorption
  • coal mine gas explosions
  • process control

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Published Papers (4 papers)

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Research

Jump to: Review

21 pages, 14008 KiB  
Article
The Pore Structure Multifractal Evolution of Vibration-Affected Tectonic Coal and the Gas Diffusion Response Characteristics
by Maoliang Shen, Zhonggang Huo, Longyong Shu, Qixian Li, Pengxin Zhang and Weihua Wang
Processes 2024, 12(8), 1701; https://doi.org/10.3390/pr12081701 - 14 Aug 2024
Viewed by 450
Abstract
Vibrations caused by downhole operations often induce coal and gas outburst accidents in tectonic zone coal seams. To clarify how vibration affects the pore structure, gas desorption, and diffusion capacity of tectonic coal, isothermal adsorption-desorption experiments under different vibration frequencies were carried out. [...] Read more.
Vibrations caused by downhole operations often induce coal and gas outburst accidents in tectonic zone coal seams. To clarify how vibration affects the pore structure, gas desorption, and diffusion capacity of tectonic coal, isothermal adsorption-desorption experiments under different vibration frequencies were carried out. In this study, high-pressure mercury intrusion experiments and low-pressure liquid nitrogen adsorption experiments were conducted to determine the pore structures of tectonic coal before and after vibration. The pore distribution of vibration-affected tectonic coal, including local concentration, heterogeneity, and connectivity, was analyzed using multifractal theory. Further, a correlation analysis was performed between the desorption diffusion characteristic parameters and the pore fractal characteristic parameters to derive the intrinsic relationship between the pore fractal evolution characteristics and the desorption diffusion characteristics. The results showed that the vibration increased the pore volume of the tectonic coal, and the pore volume increased as the vibration frequency increased in the 50 Hz range. The pore structure of the vibration-affected tectonic coal showed multifractal characteristics, and the multifractal parameters affected the gas desorption and diffusion capacity by reflecting the density, uniformity, and connectivity of the pore distribution in the coal. The increases in the desorption amount (Q), initial desorption velocity (V0), initial diffusion coefficient (D0), and initial effective diffusion coefficient (De) of the tectonic coal due to vibration indicated that the gas desorption and diffusion capacity of the tectonic coal were improved at the initial desorption stage. Q, V0, D0, and De had significant positive correlations with pore volume and the Hurst index, and V0, D0, and De had negative correlations with the Hausdorff dimension. To a certain extent, vibration reduced the local density regarding the pore distribution in the coal. As a result, the pore size distribution was more uniform, and the pore connectivity was improved, thereby enhancing the gas desorption and diffusion capacity of the coal. Full article
(This article belongs to the Special Issue Monitoring, Process Control, Simulation, and Optimization in Coal Mining)
►▼ Show Figures

Figure 1

Figure 1
<p>The schematic diagram and physical diagram of the MVGAD-I type vibration condition isothermal adsorption-desorption platform.</p> Full article ">Figure 2
<p>Size distribution and volume change characteristics of macropores and mesopores in vibration-affected tectonic coal.</p> Full article ">Figure 3
<p>Pore size distribution and volume change characteristics of minipores and micropores in vibration-affected tectonic coal.</p> Full article ">Figure 4
<p>Fitting curves between the partition function of macropores and mesopores and the interval length of vibration-affected tectonic coal.</p> Full article ">Figure 5
<p>Fitting curves between the partition function of minipores and micropores and the interval length of vibration-affected tectonic coal.</p> Full article ">Figure 6
<p>The generalized dimension spectra of the macropore and mesopore size distribution in the vibration-affected tectonic coal.</p> Full article ">Figure 7
<p>Generalized dimension spectra of the pore size distribution of vibration-affected tectonic coal.</p> Full article ">Figure 8
<p>Mass scaling function <math display="inline"><semantics> <mrow> <mi>τ</mi> <mfenced> <mi>q</mi> </mfenced> </mrow> </semantics></math> of pore size distribution of vibration-affected tectonic coal.</p> Full article ">Figure 9
<p>Classic Hurst index of vibration-affected tectonic coal pores.</p> Full article ">Figure 10
<p>Gas desorption curves of coal samples.</p> Full article ">Figure 11
<p>Initial gas desorption rate of vibration-affected tectonic coal.</p> Full article ">Figure 12
<p>Measured gas diffusion rate of coal samples fitted with the kinetic diffusion model.</p> Full article ">Figure 13
<p>Initial effective diffusion coefficient of vibration-affected tectonic coal.</p> Full article ">Figure 14
<p>Correlation matrix between pore structure parameters and desorption-diffusion parameters.</p> Full article ">
20 pages, 10455 KiB  
Article
Experimental Study on the Effect of Unloading Paths on Coal Damage and Permeability Evolution
by Congmeng Hao, Youpai Wang and Guangyi Liu
Processes 2024, 12(8), 1661; https://doi.org/10.3390/pr12081661 - 7 Aug 2024
Viewed by 774
Abstract
Coal seam cavitation is one of the most effective techniques for gas disaster control in low-permeability coal. Due to the difference in cavitation method and process, the damage degree and fracture development range of the coal body around the cavern are greatly different, [...] Read more.
Coal seam cavitation is one of the most effective techniques for gas disaster control in low-permeability coal. Due to the difference in cavitation method and process, the damage degree and fracture development range of the coal body around the cavern are greatly different, and the effect of increasing the permeability of the coal body is further changed. In order to further understand the permeability enhancement mechanism of cavitation technology on low-permeability coal and effectively guide engineering applications, this paper conducted experimental research on the unloading damage and permeability evolution characteristics of coal under different cavitation paths using a coal-rock “adsorption-percolation-mechanics” coupling test system. Through the analysis of coal strength and deformation characteristics, coal damage characteristics, and the evolution law of coal permeability combined with the macroscopic damage characteristics of coal, the strength degradation mechanism of unloaded coal and the mechanism of increased permeability and flow were revealed. The results show that unloading can significantly reduce the strength of coal, and the greater the unloading rate, the more obvious the reduction. The essence of this is that unloading reduces the cohesion and internal friction angle of coal—damage and breakage are the most effective ways to improve the permeability of the coal body. Unloading damaged coal bodies not only significantly improves the permeability of the coal body but also improves the diffusion ability of gas, and finally, shows a remarkable strengthening effect of gas extraction. Full article
(This article belongs to the Special Issue Monitoring, Process Control, Simulation, and Optimization in Coal Mining)
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic diagram of stress evolution of coal mass around the cavern with different hole expansion paths: (<b>a</b>) Hydraulic cavitation process-repeated scouring into holes; (<b>b</b>) Hydraulic cavitation process-one-time scouring into holes; (<b>c</b>) Mechanical cavitation process.</p> Full article ">Figure 2
<p>Experimental coal sample and test system: (<b>a</b>) Coal sample preparation process; (<b>b</b>) The test system.</p> Full article ">Figure 3
<p>Stress–strain characteristics of coal under different confining pressures at the same unloading rate: (<b>a</b>) conventional triaxial loading; (<b>b</b>) confining pressure unloading at 25 N/s and loading; (<b>c</b>) confining pressure unloading at 50 N/s and loading.</p> Full article ">Figure 4
<p>Stress–strain characteristics of coal under the same confining pressure and different unloading rates: (<b>a</b>) initial confining pressure of 5 MPa; (<b>b</b>) initial confining pressure of 10 MPa; (<b>c</b>) initial confining pressure of 15 MPa.</p> Full article ">Figure 5
<p>Changes of peak stress of coal samples under different initial confining pressures.</p> Full article ">Figure 6
<p>Characteristics of acoustic emission signals (AE counts) of coal samples in different unloading paths.</p> Full article ">Figure 7
<p>Characteristics of acoustic emission signals (AE energy) of coal samples in different unloading paths.</p> Full article ">Figure 8
<p>Comparison of coal acoustic emission data in different unloading paths.</p> Full article ">Figure 9
<p>Permeability evolution of coal mass during full stress–strain process under different unloading behaviors.</p> Full article ">Figure 10
<p>Macroscopic damage and destruction characteristics of coal under different unloading behaviors.</p> Full article ">Figure 11
<p>Coal damage and destruction mechanism under different unloading conditions.</p> Full article ">Figure 12
<p>Permeability evolution model of coal mass during full stress–strain process under different unloading behaviors.</p> Full article ">Figure 13
<p>The path of permeability increase caused by pressure relief and damage of coal-mass.</p> Full article ">
17 pages, 6075 KiB  
Article
Study on the Damage Mechanism of Coal under Hydraulic Load
by Hongyan Li, Yaolong Li, Weihua Wang, Yang Li, Zhongxue Sun, Shi He and Yongpeng Fan
Processes 2024, 12(5), 925; https://doi.org/10.3390/pr12050925 - 1 May 2024
Viewed by 783
Abstract
Hydraulic fracturing is extensively utilized for the prevention and control of gas outbursts and rockbursts in the deep sections of coal mines. The determination of fracturing construction parameters based on the coal seam conditions and stress environments merits further investigation. This paper constructs [...] Read more.
Hydraulic fracturing is extensively utilized for the prevention and control of gas outbursts and rockbursts in the deep sections of coal mines. The determination of fracturing construction parameters based on the coal seam conditions and stress environments merits further investigation. This paper constructs a damage analysis model for coal under hydraulic loads, factoring in the influence of the intermediate principal stress, grounded in the octahedron strength theory analysis approach. It deduces the theoretical analytical equation for the damage distribution of a coal medium subjected to small-flow-rate hydraulic fracturing in underground coal mines. Laboratory experiments yielded the mechanical parameters of coal in the study area and facilitated the fitting of the intermediate principal stress coefficient. Leveraging these datasets, the study probes into the interaction between hydraulic loads and damage radius under assorted influence ranges, porosity, far-field crustal stresses, and brittle damage coefficients. The findings underscore that hydraulic load escalates exponentially with the damage radius. Within the variable range of geological conditions in the test area, the effects of varying influence range, porosity level, far-field stress, and brittle damage coefficient on the outcomes intensify one by one; a larger hydraulic load diminishes the impact of far-field stress variations on the damage radius, inversely to the influence range, porosity, and brittle damage. The damage radius derived through the gas pressure reduction method in field applications corroborates the theoretical calculations, affirming the precision of the theoretical model. These findings render pivotal guidance for the design and efficacy assessment of small-scale hydraulic fracturing in underground coal mines. Full article
(This article belongs to the Special Issue Monitoring, Process Control, Simulation, and Optimization in Coal Mining)
►▼ Show Figures

Figure 1

Figure 1
<p>Influence zone of the coal under hydraulic loading.</p> Full article ">Figure 2
<p>Stress–strain curve of coal.</p> Full article ">Figure 3
<p>Coefficient curve of <span class="html-italic">ε<sub>c</sub></span>/<span class="html-italic">ε<sub>t</sub></span> vs. <span class="html-italic">n</span>.</p> Full article ">Figure 4
<p>GCTS RTR-4600 high-performance rock mechanics testing system and schematic diagram.</p> Full article ">Figure 5
<p>Pore volume distribution density function diagram.</p> Full article ">Figure 6
<p>Curve of damage radius <span class="html-italic">c</span> versus hydraulic water pressure <span class="html-italic">P<sub>h</sub></span> for different influence ranges <span class="html-italic">c</span> (<b>a</b>), and local magnification diagrams at <span class="html-italic">c</span> = 1 m (<b>b</b>) and <span class="html-italic">c</span> = 1.2 m (<b>c</b>).</p> Full article ">Figure 7
<p>Relation between influence range and hydraulic pressure.</p> Full article ">Figure 8
<p>Curve of damage radius <span class="html-italic">c</span> versus hydraulic water pressure <span class="html-italic">P<sub>h</sub></span> for different porosity values φ (<b>a</b>), and local magnification diagrams at <span class="html-italic">P<sub>h</sub></span> = 15 MPa (<b>b</b>) and <span class="html-italic">P<sub>h</sub></span> = 45 MPa (<b>c</b>).</p> Full article ">Figure 9
<p>Curve of damage radius <span class="html-italic">c</span> versus hydraulic water pressure <span class="html-italic">P<sub>h</sub></span> for different far-field crustal stresses <span class="html-italic">P</span><sub>0</sub>.</p> Full article ">Figure 10
<p>Curve of damage radius <span class="html-italic">c</span> versus hydraulic water pressure <span class="html-italic">P<sub>h</sub></span> for different <span class="html-italic">n</span>.</p> Full article ">Figure 11
<p>Examination of the coal body influence range by the pressure-drop method.</p> Full article ">Figure 12
<p>Proportional decline in gas pressure around the drilling hole, measured by hydraulic fracturing.</p> Full article ">

Review

Jump to: Research

44 pages, 8150 KiB  
Review
Theories, Techniques and Materials for Sealing Coalbed Methane Extraction Boreholes in Underground Mines: A Review
by Ruiqing Bi, Miaomiao Guo, Shuai Wang, Yunguang Zhang, Xiaopeng Si, Xuexi Chen and Liang Zhang
Processes 2024, 12(9), 2022; https://doi.org/10.3390/pr12092022 - 19 Sep 2024
Viewed by 524
Abstract
To further enhance the intelligent technology, platformisation, and systematisation of coalbed methane extraction sealing technology, this paper analyses the research progress of theories, technologies, and sealing materials related to coalbed methane extraction sealing and systematically summarises the latest achievements of the basic theories, [...] Read more.
To further enhance the intelligent technology, platformisation, and systematisation of coalbed methane extraction sealing technology, this paper analyses the research progress of theories, technologies, and sealing materials related to coalbed methane extraction sealing and systematically summarises the latest achievements of the basic theories, key technologies, and sealing materials of coalbed methane extraction. Considering the increasing mining depth, advancements in intelligent technology, and the evolving landscape of coalbed methane development, it is particularly important to establish a more comprehensive coalbed methane extraction borehole sealing system. Based on this, future development trends and research prospects are proposed: In terms of coalbed-methane-extraction-related theories, there should be a stronger focus on fundamental research such as on gas flow within the coal matrix. For coalbed methane extraction borehole sealing technologies and devices, efforts should be made to enhance research on intelligent, platform-based, and systematic approaches, while adapting to the application of directional long borehole sealing processes. In terms of coalbed methane extraction borehole leakage detection, non-contact measurement and non-destructive monitoring methods should be employed to achieve dynamic monitoring and early warning of methane leaks, integrating these technologies into coalbed methane extraction system platforms. For coalbed methane extraction borehole sealing materials, further development is needed for liquid sealing materials that address borehole creep and the development of fractures in surrounding rock, as well as solid sealing materials with Poisson’s ratios similar to that of the surrounding rock mass. Full article
(This article belongs to the Special Issue Monitoring, Process Control, Simulation, and Optimization in Coal Mining)
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Figure 1

Figure 1
<p>The 2023 global primary energy consumption chart [<a href="#B1-processes-12-02022" class="html-bibr">1</a>].</p> Full article ">Figure 2
<p>The 2023 global coal consumption graph [<a href="#B1-processes-12-02022" class="html-bibr">1</a>].</p> Full article ">Figure 3
<p>Applications related to gas diffusion in coal [<a href="#B33-processes-12-02022" class="html-bibr">33</a>] (reproduced with permission from Zhao, W. et al. Fuel; published by Elsevier, 2019).</p> Full article ">Figure 4
<p>Comparison between the geometrical models of the bidisperse diffusion and the dual-porosity media [<a href="#B33-processes-12-02022" class="html-bibr">33</a>] (reproduced with permission from Zhao, W. et al. Fuel; published by Elsevier, 2019).</p> Full article ">Figure 5
<p>Schematic diagram of coalbed methane extraction blocking.</p> Full article ">Figure 6
<p>Distribution of borehole deformation zones under the surrounding rock stress. I—fractured zone; II—plastic zone; III—elastic zone; IV—original stress zone [<a href="#B25-processes-12-02022" class="html-bibr">25</a>] (reproduced with permission from Wang, K. et al. Process Safety and Environmental Protection; published Elsevier; 2019).</p> Full article ">Figure 7
<p>Stress distribution of the in-seam borehole around the roadway [<a href="#B25-processes-12-02022" class="html-bibr">25</a>] (reproduced with permission from Wang, K. et al. Process Safety and Environmental Protection; published by Elsevier; 2019).</p> Full article ">Figure 8
<p>Schematic diagram of coalbed methane extraction borehole leakage fissure field [<a href="#B119-processes-12-02022" class="html-bibr">119</a>].</p> Full article ">Figure 9
<p>Schematic diagram of coalbed methane extraction borehole leakage mechanism [<a href="#B119-processes-12-02022" class="html-bibr">119</a>]. (<b>a</b>) Leakage of air from sealing material. (<b>b</b>) Air leakage from drilled loosening rings. (<b>c</b>) Air leakage from the unloading zone of the coal body.</p> Full article ">Figure 10
<p>Dual-packer to avoid the structural stage fracturing [<a href="#B28-processes-12-02022" class="html-bibr">28</a>].</p> Full article ">Figure 11
<p>The process of the polyurethane plugging method [<a href="#B9-processes-12-02022" class="html-bibr">9</a>] (reproduced with permission from Lou, Z. et al. Gas Science and Engineering; published by Elsevier; 2024).</p> Full article ">Figure 12
<p>The process of the cement plugging method [<a href="#B9-processes-12-02022" class="html-bibr">9</a>] (reproduced with permission from Lou, Z. et al. Gas Science and Engineering; published by Elsevier; 2024).</p> Full article ">Figure 13
<p>Schematic diagram of MWYZ-H active coal seam gas pressure tester.</p> Full article ">Figure 14
<p>Structure of a coal mine hydraulic fracturing straddle packer [<a href="#B203-processes-12-02022" class="html-bibr">203</a>] (reproduced with permission from Liu A., et al. Engineering Failure Analysis; published by Elsevier; 2023).</p> Full article ">Figure 15
<p>Schematic diagram of the sealing force experienced by the straddle packer [<a href="#B203-processes-12-02022" class="html-bibr">203</a>] (reproduced with permission from Liu A., et al. Engineering Failure Analysis; published by Elsevier; 2023).</p> Full article ">Figure 16
<p>Schematic diagram of structure of the end of capsules [<a href="#B203-processes-12-02022" class="html-bibr">203</a>] (reproduced with permission from Liu A, et al. Engineering Failure Analysis; published by Elsevier; 2023).</p> Full article ">Figure 17
<p>The process of the capsular bag plugging method [<a href="#B9-processes-12-02022" class="html-bibr">9</a>] (reproduced with permission from Lou, Z. et al. Gas Science and Engineering; published by Elsevier; 2024).</p> Full article ">Figure 18
<p>Schematic diagram of airbag sealing with pressure grouting to seal the hole. 1—Coal body; 2—Grouting pipe; 3—Loose ring around the borehole; 4—End airbag; 5—Slurry outlet; 6—Extraction pipe; 7—Gas flow; 8—Grouting material; 9—Injection one-way needle valve; 10—Through.</p> Full article ">
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