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18 pages, 5734 KiB

Open AccessArticle

Multi-Index Geophysical Monitoring and Early Warning for Rockburst in Coalmine: A Case Study

by Xiaofei Liu, Siqing Zhang, Enyuan Wang, Zhibo Zhang, Yong Wang and Shengli Yang

Int. J. Environ. Res. Public Health 2023, 20(1), 392; https://doi.org/10.3390/ijerph20010392 - 26 Dec 2022

Cited by 5 | Viewed by 1884

Abstract

Rockburst is a major disaster in deep mining, restricting the safety and the production efficiency of the Laohutai Coal Mine in Fushun, Liaoning Province. To predict and prevent coalmine rockbursts, a comprehensive method based on multi-instrument monitoring is proposed by using a YDD16 [...] Read more.

Rockburst is a major disaster in deep mining, restricting the safety and the production efficiency of the Laohutai Coal Mine in Fushun, Liaoning Province. To predict and prevent coalmine rockbursts, a comprehensive method based on multi-instrument monitoring is proposed by using a YDD16 acoustic-electromagnetic monitor and microseismic monitoring system, including microseismic (MS) monitoring, electromagnetic radiation (EMR) monitoring, and acoustic emission (AE) monitoring. Field investigation shows that MS, AE, and EMR signals have abnormal precursors before rockbursts in a new working face. Based on the fluctuation theory and D-S evidence theory, the multi-index geophysical monitoring and early warning technology for rockburst disasters in the Laohutai Coal Mine are established. The method has been applied to the prediction of rockbursts in the Laohutai Coal Mine. The application shows that the acoustic-electromagnetic synchronous monitoring and early warning technology can accurately identify the potential rockburst risk and trigger an early warning, which is more reliable than a single method. The case study of the Laohutai rockburst shows that the joint early warning method of multi-instrument comprehensive monitoring can predict the possibility of rockbursts. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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16 pages, 4245 KiB

Open AccessArticle

Abutment Pressure Distribution Law and Support Analysis of Super Large Mining Height Face

by Libo Zhang, Wenlong Shen, Xuelong Li, Yabo Wang, Qizhi Qin, Xutao Lu and Tianxi Xue

Int. J. Environ. Res. Public Health 2023, 20(1), 227; https://doi.org/10.3390/ijerph20010227 - 23 Dec 2022

Cited by 48 | Viewed by 1699

Abstract

Under the condition of the shallow coal seam, the laws of roof activity after large mining height longwall face mining and prevention measures for large-area roof weighting are problems that need to be solved urgently. In the background of the super large mining [...] Read more.

Under the condition of the shallow coal seam, the laws of roof activity after large mining height longwall face mining and prevention measures for large-area roof weighting are problems that need to be solved urgently. In the background of the super large mining height working face in the upper 108 working face of Jinjitan Coal Mine 12-2, the spatial distribution characteristics of the development and change of the mining-induced abutment pressure and the related support design in the 8.2 m super large mining height and fully mechanized mining face were conducted. It reveals the distribution characteristics of the dynamic stress field and internal and external stress fields. The influence range of the abutment pressure of the super high mining height working face was measured on site. The numerical simulation is carried out, the roadway support structure is analyzed, and the improvement measures are proposed. The research results demonstrate that: The influence range of abutment pressure is 234 m, the obvious influence range of the leading pressure is 47–60 m, and the peak position of the influence of the leading pressure is 15–20 m. The 5 m range is the lateral inward stress field of the coal pillar, the 10–15 m range is the outward stress field of the coal pillar, and the 20 m range is the original rock stress field of the coal pillar. Therefore, it is proposed that the reasonable size of the coal pillar for roadway protection is 20–22 m. Adjusting the distance between screw steel and FRP bolts from 1000 mm to 1200 mm, the length of the roof prestressed anchor cable should be appropriately reduced to 5.5–6 m according to the lithology of the roof. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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17 pages, 6531 KiB

Open AccessArticle

Influence of Confining Pressure on Nonlinear Failure Characteristics of Coal Subjected to Triaxial Compression

by Qiuping Li, Jie Liu, Shouqing Lu, Zaiquan Wang, Hao Wang, Yimeng Wu, Yupu Wang, Di Ying and Mingjie Li

Int. J. Environ. Res. Public Health 2023, 20(1), 105; https://doi.org/10.3390/ijerph20010105 - 21 Dec 2022

Cited by 1 | Viewed by 1058

Abstract

The stress of a coal seam increases with an increase in the mining depth, which makes the failure mechanism of a coal mass more complex. To reveal the deformation and failure law of deep coal, a series of triaxial experiments was carried out [...] Read more.

The stress of a coal seam increases with an increase in the mining depth, which makes the failure mechanism of a coal mass more complex. To reveal the deformation and failure law of deep coal, a series of triaxial experiments was carried out via laboratory experiments and numerical simulation experiments to analyze the influence of the confining stress on the nonlinear failure characteristics of coal. Based on the crack-propagation model, the values for the inelastic flexibility S₁ and the damage variable D were calculated. The results showed that the value of S₁ decreased with an increase in the confining stress, which indicated that the increase in the confining pressure could inhibit the crack propagation and that the inhibitory effect was more obvious when the confining pressure increased in a small range of 4 to 12 MPa. The damage variable decreased with an increase in the confining pressure at the yield point; moreover, with an increase in the initial confining pressure, the damage rate gradually decreased. The coal body changed from the compression state to the expansion state when moving from the yield point to the peak point, and the compression value of the yield point and the dilation value of the peak point increased with the increase in the confining pressure. After the coal body entered the yield stage, the change in the confining pressure had a more significant effect on the damage to the coal body. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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24 pages, 8850 KiB

Open AccessArticle

Research on the Creep Model of Deep Coal Roadway and Its Numerical Simulation Reproduction

by Qiming Zhang, Enyuan Wang and Zeng Ding

Int. J. Environ. Res. Public Health 2022, 19(23), 15920; https://doi.org/10.3390/ijerph192315920 - 29 Nov 2022

Viewed by 1089

Abstract

The long-term stability of coal mine roadway engineering is critical to the safe mining of coal resources and the protection of the surface environment. In this paper, the creep test of coal samples in coal roadway was carried out by multi-stage constant load [...] Read more.

The long-term stability of coal mine roadway engineering is critical to the safe mining of coal resources and the protection of the surface environment. In this paper, the creep test of coal samples in coal roadway was carried out by multi-stage constant load method, and the test results showed that when the stress level was low, the creep curve had a attenuated stage and a steady-state stage, and the steady-state creep rate tended to increase with the increase in the stress level; When the stress level was higher than the yield stress, the creep rate curve appeared to have an acceleration stage after the steady-state stage. The instability failure mode of the coal sample was mainly shear failure with local tension failure. For this, a New Fractional-order Nonlinear Viscoelastic-plastic Rheological Model (NFNVRM) was established by introducing Abel elements and Nonlinear elements, and the constitutive equation of the model was deduced. The new model can fully reflect the stable decay stage and accelerated rheological stages of coal samples, and the parameter identification curve was consistent with the experimental results, which verifies the correctness and reasonableness of the NFNVRM. Meanwhile, based on the FLAC3D secondary development interface, the constitutive equations of the NFNVRM were written into the software to obtain new Dynamic Link Library (DLL) files. The simulation results were consistent with the experimental results when the DLL file was called. Finally, the NFNVRM.dll was applied to predict the surrounding rock deformation of an S mine. The study’s findings offer suggestions for environmental protection. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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22 pages, 4700 KiB

Open AccessArticle

Microseismic Dynamic Response and Multi-Source Warning during Rockburst Monitoring Based on Weight Decision Analysis

by Jiawei Tian, Dong Chen, Zhentang Liu and Weichen Sun

Int. J. Environ. Res. Public Health 2022, 19(23), 15698; https://doi.org/10.3390/ijerph192315698 - 25 Nov 2022

Cited by 3 | Viewed by 1125

Abstract

To prevent rockburst disasters and improve the accuracy of warnings for rockburst, based on the microseismic data of the 1366 working face of Hengda Coal Mine collected by the microseismic monitoring system, Fourier transform, wavelet packet transform, and Hilbert–Huang transform analysis methods are [...] Read more.

To prevent rockburst disasters and improve the accuracy of warnings for rockburst, based on the microseismic data of the 1366 working face of Hengda Coal Mine collected by the microseismic monitoring system, Fourier transform, wavelet packet transform, and Hilbert–Huang transform analysis methods are used for time-frequency domain joint analysis. The time-frequency differences of the main frequency, amplitude, frequency band percentage, and instantaneous energy of the high-energy microseismic event and the events before high-energy microseismic event are obtained. The analysis shows that the high-energy event has obvious low frequency characteristics, and when the high-energy event occurs, the instantaneous energy shows an obvious “inverted V” trend. At the same time, it is found that the acoustoelectric indexes show a trend of “rising” or “inverted V” when the high-energy event occurs. On this basis, the unascertained measure comprehensive evaluation model of rock burst hazard is established by analytic hierarchy process (AHP). Based on the analysis of microseismic data and the acoustoelectric index of the 1366 working face in Hengda coal mine, it is of great significance to determine the warning indicators for rockburst, improve the accuracy of uncertainty quantitative analysis for rockburst, and improve the discrimination accuracy of rockburst risk. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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16 pages, 21284 KiB

Open AccessArticle

Analysis of Acoustic Emission Characteristics and Failure Mode of Deep Surrounding Rock of Sanshandao Gold Mine

by Guang Li, Rong Lu, Fengshan Ma and Jie Guo

Int. J. Environ. Res. Public Health 2022, 19(20), 13351; https://doi.org/10.3390/ijerph192013351 - 16 Oct 2022

Cited by 2 | Viewed by 1298

Abstract

In mining engineering, crack distribution has a considerable influence on the mechanical behavior and stability of the surrounding rock mass. Using the granite of the Sanshandao gold mine as experimental samples, the deformation and failure of fractured rock were analyzed based on a [...] Read more.

In mining engineering, crack distribution has a considerable influence on the mechanical behavior and stability of the surrounding rock mass. Using the granite of the Sanshandao gold mine as experimental samples, the deformation and failure of fractured rock were analyzed based on a rock uniaxial compression test with acoustic emission monitoring. We analyzed the characteristics of different stages of rock sample deformation, and evaluated the failure mode of seven types of rock samples. The results show that the cracks had a considerable impact on rock sample strength and mechanical behavior, and the strength of intact rock was the highest, while that of the sample with parallel double cracks was the lowest. The acoustic emission parameters, AF, RA, and lg(AF/RA), have different change trends in different stages of rock deformation and failure. Based on these change trends, the failure modes of rock samples with different crack distributions were identified. Additionally, for the rock samples with seven types of crack distribution, a sudden or progressive failure caused by the b-value curves was observed. The research findings provide a database for deep surrounding rock stability in the study area and provide suggestions for failure prediction. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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16 pages, 4387 KiB

Open AccessArticle

Study on Safety Coefficient of Sedimentary Bauxite Strip Pillar under Valley Terrain

by Lichun Jiang, Huazhe Jiao, Bo Xie and Han Yang

Int. J. Environ. Res. Public Health 2022, 19(17), 10991; https://doi.org/10.3390/ijerph191710991 - 02 Sep 2022

Cited by 1 | Viewed by 1135

Abstract

The underground sedimentary bauxite ore body in Shanxi province has a shallow burial depth; the valley terrain caused stress concentration on a pillar which affected the pillar’s safety and goaf stability. This paper proposed a pillar safety coefficient calculation method affected by the [...] Read more.

The underground sedimentary bauxite ore body in Shanxi province has a shallow burial depth; the valley terrain caused stress concentration on a pillar which affected the pillar’s safety and goaf stability. This paper proposed a pillar safety coefficient calculation method affected by the goaf structural parameters and the valley terrain, which was based on a pillar mechanics analysis under the valley terrain. The results show that the overlying valley terrain will cause stress concentration on the pillar, reducing the adequate bearing capacity and the pillar stability. The increase of the goaf span b and the height of the pillar h is extensively detrimental to pillar stability. Meanwhile, increasing the pillar burial depth would cause the pillar to weaken, but can effectively decrease the influence of the valley terrain. Furthermore, when the angle between the goaf strike and the valley strike β < 50°, β has a more significant impact on the stress concentration and safety coefficient. The stability of an underground sedimentary bauxite pillar is calculated by the method, the result complied with the actual situation. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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11 pages, 2686 KiB

Open AccessArticle

Shallow Failure of Weak Slopes in Bayan Obo West Mine

by Wencai Wang, Yongfu Yan, Yue Qu and Pengfei Wang

Int. J. Environ. Res. Public Health 2022, 19(15), 9755; https://doi.org/10.3390/ijerph19159755 - 08 Aug 2022

Cited by 2 | Viewed by 1276

Abstract

The slope stability of large open-pit mines has always been a concern and the analysis of large-scale slope landslides is a focus. However, shallow failure in soft rock slopes also has a serious impact on safe production. The northern slope of Baiyunebo West [...] Read more.

The slope stability of large open-pit mines has always been a concern and the analysis of large-scale slope landslides is a focus. However, shallow failure in soft rock slopes also has a serious impact on safe production. The northern slope of Baiyunebo West Mine has many shallow landslides in the final slope, resulting in damage of the maintenance channel of the belt transportation system, which has a serious impact on the safety of production. In order to reduce the shallow failure in weak rock slope, it is necessary to analyze the behavior and characteristics of shallow failure in weak rock. Firstly, the mechanical parameters of the intact rock were obtained by using the exploration data; secondly, through the analysis of blasting-damage range, the distribution characteristics of fractures after the failure of weak rock were obtained. Finally, through theoretical analysis, numerical simulation, surface displacement monitoring and on-site shallow-failure case analysis, the deformation and characteristics of shallow failure of weak rock slope in West Mine were obtained. It was found that the mechanical parameters of rock mass strength on the surface of weak rock slope and the original rock were quite different after mining disturbance. The mode of failure of shallow weak rock slope in the West Mine was creep-cracking; the numerical modelling analysis was carried out by using the assignment method of shallow lithology weakening and gradual change, which is more in line with the deformation characteristics of weak rock slope in West Mine. The lower deformation of the soft rock slope in West Mine is 3–5 times that of the upper deformation. The research results are helpful to understand the influence of blasting on the stability of soft rock slope. At present, West Mine has started to adjust blasting parameters according to the research results, so as to reduce the excessive damage of blasting to rock mass, so the stability of the slope is improved. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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18 pages, 7145 KiB

Open AccessArticle

Experimental Investigation on Mechanical and Acoustic Emission Characteristics of Gassy Coal under Different Stress Paths

by Jie Liu, Qiuping Li, Jinduo Li, Zaiquan Wang and Shouqing Lu

Int. J. Environ. Res. Public Health 2022, 19(13), 7873; https://doi.org/10.3390/ijerph19137873 - 27 Jun 2022

Cited by 5 | Viewed by 1314

Abstract

Coal mining leads to stress loading–unloading variation in front of the working face, which influences the occurrence of disasters. In order to study the influence mechanism of stress loading–unloading to the coal failure, a series of experiments of gas-bearing coal deformation and failure [...] Read more.

Coal mining leads to stress loading–unloading variation in front of the working face, which influences the occurrence of disasters. In order to study the influence mechanism of stress loading–unloading to the coal failure, a series of experiments of gas-bearing coal deformation and failure under triaxial stress were conducted and acoustic emission (AE) was monitored. In this study, the effect of gas pressure on the mechanical behavior of gas-bearing coal in conventional triaxial stress (CTS) experiments and fixed axial stress and unloading confining stress (FASUCS) experiments was analyzed, and the damage evolution rules of gas-bearing coal in the CTS experiments and FASUCS experiments were determined using AE. The results show that with the increasing of gas pressure, the peak strength and peak strain of gas-bearing coal in the CTS experiments and FASUCS experiments gradually decrease, and the peak of AE ring-down counts lags behind the peak strength. Compared with the CTS experiments, the strength of gas-bearing coal in the FASUCS experiments is lower and the precursor information appears later. The trends in calculated stress and damage coefficient D are consistent with the stress path during unloading, and both begin to rise sharply after the sample enters the plastic stage. Therefore, AE ring-down counts, damage coefficient D, and calculated stress can be used as precursor information for failure of coal and rock, which has great significance for the further study of coal-rock material and for early hazard warning. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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23 pages, 9389 KiB

Open AccessArticle

Focal Mechanism and Source Parameters Analysis of Mining-Induced Earthquakes Based on Relative Moment Tensor Inversion

by Anye Cao, Yaoqi Liu, Fan Chen, Qi Hao, Xu Yang, Changbin Wang and Xianxi Bai

Int. J. Environ. Res. Public Health 2022, 19(12), 7352; https://doi.org/10.3390/ijerph19127352 - 15 Jun 2022

Cited by 6 | Viewed by 1800

Abstract

Mining-induced earthquakes (MIEs) in underground coal mines have been a common phenomenon that easily triggers rock bursts, but the mechanism is not understood clearly. This research investigates the laws of focal mechanism and source parameters based on focal mechanism and source parameters analysis [...] Read more.

Mining-induced earthquakes (MIEs) in underground coal mines have been a common phenomenon that easily triggers rock bursts, but the mechanism is not understood clearly. This research investigates the laws of focal mechanism and source parameters based on focal mechanism and source parameters analysis of MIEs in three frequent rock burst areas. The relative moment tensor inversion (MTI) method was introduced, and the way to construct the inversion matrix was modified. The minimum ray and source number conditions were calculated, and an optimized identification criterion for source rupture type was proposed. Results show that the geological structure, stress environment, and source horizon influence the focal mechanism. The tensile type sources can distribute in the roof and coal seam, while the shear types are primarily located in the coal seam. In the typical fold structure area, the difference in source rupture strength and stress adjustment between tensile and shear types is negligible, while the disturbance scale of tensile types is distinct. The shear types have higher apparent volume and seismic moment in the deep buried fault area but lower source energy. The apparent stress of the tensile types is higher than that of the shear types, representing that the stress concentration still exists in the roof after the MIEs, but the stress near the faults could be effectively released. In the high-stress roadway pillar area, the primary fracture of the coal pillar easily produces a continuous shear rupture along the dominant stress direction under the extrusion of the roof and floor. The source parameters (except apparent stress) of shear types are higher than tensile types and have higher dynamic risk. The results contribute to expanding the understanding of rock burst mechanisms and guide MIEs’ prevention. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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19 pages, 4171 KiB

Open AccessArticle

Determination of Key Technical Parameters in the Study of New Pressure Sealing Technology for Coal Seam Gas Extraction

by Zhongguang Sun, Xuelong Li, Kequan Wang, Fakai Wang, Deyou Chen and Zhen Li

Int. J. Environ. Res. Public Health 2022, 19(9), 4968; https://doi.org/10.3390/ijerph19094968 - 19 Apr 2022

Cited by 5 | Viewed by 1539

Abstract

Coal is affected by the concentrated stress disturbance of mining, the disturbance of drilling hole formation, and the concentrated stress of coal shrinkage and splitting of gas desorption from the hole wall; these result in a large number of secondary cracks that collect [...] Read more.

Coal is affected by the concentrated stress disturbance of mining, the disturbance of drilling hole formation, and the concentrated stress of coal shrinkage and splitting of gas desorption from the hole wall; these result in a large number of secondary cracks that collect and leak gas. As a result, it is difficult for the coal seam sealing process to meet engineering quality sealing requirements, which results in problems such as low gas concentration during the extraction process. In this paper, based on the analysis of coal pore and fissure characteristics, and in view of the current situation of gas drainage and sealing in this coal seam, combined with the existing grouting and sealing technology, it is proposed to use pressure grouting and sealing to realize the sealing of deep coal bodies in the hole wall. According to the field conditions, the experimental pressure sealing parameter index is as follows: theoretical sealing length L₁ = 9.69 m, the sealing length L₂ = 13.98 m is verified, and the final sealing length is determined to be 15 m; the sealing radius is determined to be 0.6 m; the cement slurry was prepared on site with a water: cement ratio of 2:1; P_G = 0.43 MPa was calculated; the range of the slurry diffusion radius R was 93.4–176.6 cm; the grouting pressure was determined to be 0.516 MPa. Field application practice has proved that: (1) Under the same drilling parameters and sealing parameters, the gas drainage effect of drilling with pressure sealing is 2.3 times higher than that without pressure sealing; (2) Using traditional sealing technology for drilling holes, the gas extraction concentration is far lower than the sealing operation effect of using the pressure sealing process; (3) Reasonably extending the length of the gas extraction drilling and sealing is a basic guarantee for realizing a substantial increase in the gas extraction concentration; (4) Sealing with pressure leads to a reliable and stable hole process. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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12 pages, 6742 KiB

Open AccessArticle

A Gas Pressure Prediction Model of the Excavation Face Based on Gas Emission

by Liang Chen and Qi Liu

Int. J. Environ. Res. Public Health 2022, 19(8), 4891; https://doi.org/10.3390/ijerph19084891 - 18 Apr 2022

Cited by 2 | Viewed by 1400

Abstract

Gas pressure is one of the important factors related to the occurrence of coal and gas outburst disasters. The accurate gas pressure forecasting is of significance for the prevention and control of a gas disaster. In this work, a gas pressure prediction model [...] Read more.

Gas pressure is one of the important factors related to the occurrence of coal and gas outburst disasters. The accurate gas pressure forecasting is of significance for the prevention and control of a gas disaster. In this work, a gas pressure prediction model based on the sources of gas emissions was established. The verified results show that the predicted gas pressure was roughly consistent with the actual situation. This model could meet the needs of engineering projects. Coal and gas outburst dynamic phenomenon are successfully predicted in an engineering application using the model. Overall, the prediction of coal and gas outburst using the gas pressure model achieves a continuous and dynamic effect. The model can overcome both the static and sampling shortcomings of traditional methods and solve the difficulty of coal and gas outburst prediction at the excavation face. With its broad applicability and potential prospects, the model is of great importance for guiding gas drainage, and the prevention of coal and gas outburst disasters. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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11 pages, 3666 KiB

Open AccessArticle

An Investigation on the Impact of Unloading Rate on Coal Mechanical Properties and Energy Evolution Law

by Hongjun Guo, Zhongguang Sun, Ming Ji, Yongfeng Wu and Lihui Nian

Int. J. Environ. Res. Public Health 2022, 19(8), 4546; https://doi.org/10.3390/ijerph19084546 - 09 Apr 2022

Cited by 4 | Viewed by 1299

Abstract

In order to further explore the relationship between the excavation speed and the damage of surrounding rocks and dynamic manifestation, the stress paths of unloading confining pressure and loading axial pressure were designed based on the changes in the roadway surrounding rock stress [...] Read more.

In order to further explore the relationship between the excavation speed and the damage of surrounding rocks and dynamic manifestation, the stress paths of unloading confining pressure and loading axial pressure were designed based on the changes in the roadway surrounding rock stress in this study. Additionally, the mechanical properties and energy evolution law of the coal body were investigated under various unloading rates. As the unloading rate increased, the mechanical properties of the coal body including the failure strength, the confining pressure, the axial strain, and horizontal strain tended to decrease at the rupture stage, while the volume strain and the elastic modulus increased, indicating that the rupture form evolved from the ductile failure to brittle failure. Regarding the energy, the axial pressure did positive work while the confining pressure did negative work, with the total work and the stored elastic strain energy decreasing. In addition, with the increase of the dissipation energy, the elastic strain energy conversion rate decreased linearly, indicating that the high unloading rate increased the possibility of dynamic disasters induced by the instantaneous brittle rupture of the coal body. On the other hand, due to the low releasable elastic strain energy stored in the coal body, the strength and probability of subsequent dynamic manifestation of coal body destruction were reduced. Therefore, increasing the excavation speed in a controllable way can benefit the safety of mining. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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19 pages, 8841 KiB

Open AccessArticle

Numerical Investigation of Safety Strategy for Gas Disaster Prevention in Successive Panels Using Upper Protective Layer Mining: A Case Study

by Yankun Ma, Longyong Shu, Hongyan Li, Cong Cui, Yang Zhou and Yang Li

Int. J. Environ. Res. Public Health 2022, 19(7), 4408; https://doi.org/10.3390/ijerph19074408 - 06 Apr 2022

Cited by 4 | Viewed by 1520

Abstract

Mine gas disasters are a major safety concern in underground coal mining. Protective layer mining is widely used in gas disaster control, but there are limited theoretical and experimental results that can provide guidance for site-specific mining circumstances. Taking the Xinji No. 1 [...] Read more.

Mine gas disasters are a major safety concern in underground coal mining. Protective layer mining is widely used in gas disaster control, but there are limited theoretical and experimental results that can provide guidance for site-specific mining circumstances. Taking the Xinji No. 1 mine as an example, gas disaster treatments were conducted in a new panel with overlying goaf located 85 m above the coal mine and adjacent goaf located at 30 m intervals. This study involved a comprehensive investigation, which included four steps: the selection of the first mining face, gas control and prevention, tracking and investigation, and effect analysis and assessment. The safety strategy focused on gas control planning in new mining areas or panels. The distribution and evolution characteristics of the stress, the gas permeability coefficient and the deformation volume within the protected layer were determined by numerical simulation. The coal deformation, gas emission and extraction effect were analyzed by field observation. The deformation and gas permeability of the coal seam were consistent with the stress evolution, for which the maximum compressional and expansional deformation of 6-1 coal were 18‰ and 28‰, respectively. Gas disaster control and prevention treatment of the mining face produced a significant protective effect on the underlying No. 6-1 coal seam. This work is beneficial for the planning of gas control in successive panels. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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21 pages, 6266 KiB

Open AccessArticle

Study on Filling Support Design and Ground Pressure Monitoring Scheme for Gob-Side Entry Retention by Roof Cutting and Pressure Relief in High-Gas Thin Coal Seam

by Hui Li, Haodong Zu, Kanglin Zhang and Jifa Qian

Int. J. Environ. Res. Public Health 2022, 19(7), 3913; https://doi.org/10.3390/ijerph19073913 - 25 Mar 2022

Cited by 5 | Viewed by 1882

Abstract

To ensure the successful application of roof cutting and pressure relief in the gob, to retain the roadway in a high-gas thin coal seam, by taking the 2109 working face of the Mingxin coal mine as the engineering background, this paper comprehensively analyzes [...] Read more.

To ensure the successful application of roof cutting and pressure relief in the gob, to retain the roadway in a high-gas thin coal seam, by taking the 2109 working face of the Mingxin coal mine as the engineering background, this paper comprehensively analyzes and studies the key parameters of high-water material filling and support and the law of ground pressure behavior. The results show that the high-water material filling body has the characteristics of high strength, rapid resistance increase, strong flexibility and high strength in the later stage, which can meet the requirements for retaining roadway support along the goaf. On this basis, we determined that the water-cement ratio for a high-water material filling body is 1.5:1 and the filling length, height and width each time are 3.6 m, 2.2 m and 1.0 m, respectively. In addition, a ground-pressure monitoring scheme for retaining the roadway along the goaf is put forward and the results show that the displacement of the roof and floor and the deformation of the filling body are both within a reasonable range, which proves high-water material filling support can effectively ensure the stability and integrity of the roof of the gob, thus retaining the roadway in a high-gas thin coal seam. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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19 pages, 1958 KiB

Open AccessArticle

Stability Risk Assessment of Underground Rock Pillars Using Logistic Model Trees

by Ning Li, Masoud Zare, Congke Yi and Rafael Jimenez

Int. J. Environ. Res. Public Health 2022, 19(4), 2136; https://doi.org/10.3390/ijerph19042136 - 14 Feb 2022

Cited by 8 | Viewed by 1587

Abstract

Pillars are important structural elements that provide temporary or permanent support in underground spaces. Unstable pillars can result in rock sloughing leading to roof collapse, and they can also cause rock burst. Hence, the prediction of underground pillar stability is important. This paper [...] Read more.

Pillars are important structural elements that provide temporary or permanent support in underground spaces. Unstable pillars can result in rock sloughing leading to roof collapse, and they can also cause rock burst. Hence, the prediction of underground pillar stability is important. This paper presents a novel application of Logistic Model Trees (LMT) to predict underground pillar stability. Seven parameters—pillar width, pillar height, ratio of pillar width to height, uniaxial compressive strength of rock, average pillar stress, underground depth, and Bord width—are employed to construct LMTs for rock and coal pillars. The LogitBoost algorithm is applied to train on two data sets of rock and coal pillar case histories. The two models are validated with (i) 10-fold cross-validation and with (ii) another set of new case histories. Results suggest that the accuracy of the proposed LMT is the highest among other common machine learning methods previously employed in the literature. Moreover, a sensitivity analysis indicates that the average stress, p, and the ratio of pillar width to height, r, are the most influential parameters for the proposed models. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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17 pages, 2618 KiB

Open AccessArticle

The Temperature Field Evolution and Water Migration Law of Coal under Low-Temperature Freezing Conditions

by Bo Li, Li Li, Laisheng Huang and Xiaoquan Lv

Int. J. Environ. Res. Public Health 2021, 18(24), 13188; https://doi.org/10.3390/ijerph182413188 - 14 Dec 2021

Cited by 3 | Viewed by 1941

Abstract

This study examines the evolution law of the coal temperature field under low-temperature freezing conditions. The temperature inside coal samples with different water contents was measured in real-time at several measurement points in different locations inside the sample under the condition of low-temperature [...] Read more.

This study examines the evolution law of the coal temperature field under low-temperature freezing conditions. The temperature inside coal samples with different water contents was measured in real-time at several measurement points in different locations inside the sample under the condition of low-temperature medium (liquid nitrogen) freezing. The temperature change curve was then used to analyse the laws of temperature propagation and the movement of the freezing front of the coal, which revealed the mechanism of internal water migration in the coal under low-temperature freezing conditions. The results indicate that the greater the water content of the coal sample, the greater the temperature propagation rate. The reasons for this are the phase change of ice and water inside the coal during the freezing process; the increase in the contact area of the ice and coal matrix caused by the volume expansion; and the joint action of the two. The process of the movement of the freezing front is due to the greater adsorption force of the ice lens than that of the coal matrix. Thus, the water molecules adsorbed in the unfrozen area of the coal matrix migrate towards the freezing front and form a new ice lens. Considering the temperature gradient and water content of the coal samples, Darcy’s permeation equation and water migration equation for the inside of the coal under freezing conditions were derived, and the segregation potential and matrix potential were analysed. The obtained theoretical and experimental results were found to be consistent. The higher the water content of the coal samples, the smaller the matrix potential for the hindrance of water migration. Furthermore, the larger the temperature gradient, the larger the segregation potential, and the faster the water migration rate. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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Cause Analysis and Preventive Measures of Guizhou D2809 Train Derailment Accident in Guizhou, China on 4 June 2022

by Yan-Ning Wang, Han Chen, Bin-Song Jiang, Jing-Rui Peng and Jun Chen

Int. J. Environ. Res. Public Health 2022, 19(24), 17003; https://doi.org/10.3390/ijerph192417003 - 18 Dec 2022

Cited by 1 | Viewed by 2305

Abstract

This paper summarizes the cause of the debris flow impact train accident by investigating the local geological condition, meteorological data and field investigation that happened in Guizhou, China on 4 June 2022. The result showed that the major reason is the continuous heavy [...] Read more.

This paper summarizes the cause of the debris flow impact train accident by investigating the local geological condition, meteorological data and field investigation that happened in Guizhou, China on 4 June 2022. The result showed that the major reason is the continuous heavy rain in the surrounding area, which led to a small landslide at the upper right of the tunnel entrance. Besides, the construction of the Jianrong Expressway in the upper reaches increased the catchment area, which makes the water content of the upper soil increase while the shear strength decreases. Such large-scale catastrophic accidents significantly threaten the local environment and public safety. Therefore, it is urgent to pay special attention to the changes in geological conditions along the line, especially the adverse effects of construction, to improve the early risk warning and post-accident treatment ability. Full article

(This article belongs to the Special Issue Full Life-Cycle Safety Management of Coal and Rock Dynamic Disasters)

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