Research

22 pages, 3594 KiB

Open AccessArticle

Decision Intelligence-Based Predictive Modelling of Hard Rock Pillar Stability Using K-Nearest Neighbour Coupled with Grey Wolf Optimization Algorithm

by Muhammad Kamran, Waseem Chaudhry, Blessing Olamide Taiwo, Shahab Hosseini and Hafeezur Rehman

Processes 2024, 12(4), 783; https://doi.org/10.3390/pr12040783 - 13 Apr 2024

Viewed by 296

Abstract

Pillar stability is of paramount importance in ensuring the safety of underground rock engineering structures. The stability of pillars directly influences the structural integrity of the mine and mitigates the risk of collapses or accidents. Therefore, assessing pillar stability is crucial for safe, [...] Read more.

Pillar stability is of paramount importance in ensuring the safety of underground rock engineering structures. The stability of pillars directly influences the structural integrity of the mine and mitigates the risk of collapses or accidents. Therefore, assessing pillar stability is crucial for safe, productive, reliable, and profitable underground mining engineering processes. This study developed the application of decision intelligence-based predictive modelling of hard rock pillar stability in underground engineering structures using K-Nearest Neighbour coupled with the grey wolf optimization algorithm (KNN-GWO). Initially, a substantial dataset consisting of 236 different pillar cases was collected from seven underground hard rock mining engineering projects. This dataset was gathered by considering five significant input variables, namely pillar width, pillar height, pillar width/height ratio, uniaxial compressive strength, and average pillar stress. Secondly, the original hard rock pillar stability level has been classified into three types: failed, unstable, and stable, based on the pillar’s instability mechanism and failure process. Thirdly, several visual relationships were established in order to ascertain the correlation between input variables and the corresponding pillar stability level. Fourthly, the entire pillar database was randomly divided into a training dataset and testing dataset with a 70:30 sampling method. Moreover, the (KNN-GWO) model was developed to predict the stability of pillars in hard rock mining. Lastly, the performance of the suggested predictive model was evaluated using accuracy, precision, recall, F1-score, and a confusion matrix. The findings of the proposed model offer a superior benchmark for accurately predicting the stability of hard rock pillars. Therefore, it is recommended to employ decision intelligence models in mining engineering in order to effectively prioritise safety measures and improve the efficiency of operational processes, risk management, and decision-making related to underground engineering structures. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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19 pages, 5690 KiB

Open AccessArticle

Analysis of Rock Burst Mechanism in Extra-Thick Coal Seam Controlled by Thrust Fault under Mining Disturbance

by Suihan Yang, Xiangzhi Wei, Linlin Chen, Zhiliu Wang and Wen Wang

Processes 2024, 12(2), 320; https://doi.org/10.3390/pr12020320 - 02 Feb 2024

Viewed by 534

Abstract

A fault is a common geological structure encountered in underground coal mining. Interactions between the discontinuous structure of a fault and mining activities are the key factors in controlling the rock bursts induced by the fault. It is of great importance to study [...] Read more.

A fault is a common geological structure encountered in underground coal mining. Interactions between the discontinuous structure of a fault and mining activities are the key factors in controlling the rock bursts induced by the fault. It is of great importance to study the rock burst mechanism of an extra-thick coal seam under the combined influence of reverse faults and coal mining for the prediction and prevention of rock burst. In this study, we establish a sliding dynamics model of rock mass in a fault zone and analyze the mechanical distribution of fault-induced rock bursts under the combined action of mining disturbances. Additionally, we utilize theoretical calculation and a 3D numerical simulation method to clarify the rockburst mechanism in an extra-thick coal seam controlled by a thrust fault under mining disturbance and a fault. The results showed that the distribution range of the shear stress increment in the fault footwall was larger than that in the hanging wall, revealing a skewed distribution. The fault dip angle and mining thickness exhibit significant influence on the structure around the fault. With increases in the dip angle of the fault and mining thickness, the maximum vertical stress and peak stress first increase and then decrease. A position 80 m away from the fault is the dividing line between the fault-non-affected area and the fault-affected area. The 13,200 working face of the Gengcun coal mine is used as a case study to study the influence of mining disturbances on microseismic events. The results of this study are in good agreement with the theoretical calculations and numerical simulation results. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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18 pages, 896 KiB

Open AccessArticle

Study on the Effectiveness of the Integral Emergency Response System for Coal Mine Water Hazard Accidents Based on Combination Weighting

by Yu Hao, Huanhuan Yang, Lijun Zhang and Chaolun Sun

Processes 2024, 12(1), 235; https://doi.org/10.3390/pr12010235 - 22 Jan 2024

Cited by 1 | Viewed by 697

Abstract

Improving the emergency response effectiveness of coal mines in response to water hazard accidents not only plays a vital part in minimizing the resultant losses, but also functions as an important index for evaluating the emergency response capability of coal mines. Therefore, it [...] Read more.

Improving the emergency response effectiveness of coal mines in response to water hazard accidents not only plays a vital part in minimizing the resultant losses, but also functions as an important index for evaluating the emergency response capability of coal mines. Therefore, it is of great necessity to test the emergency response capability of coal mines. In this study, an effectiveness measurement index system for the emergency response system that comprises two primary indexes (i.e., response capability and service capability) and six secondary indexes (i.e., accident information transmission, emergency command and control, emergency rescue and mitigation, emergency management, personnel team, and prevention and preparation) was constructed. Additionally, a technique for order preference by similarity to ideal solution (TOPSIS) model for evaluating the effectiveness of the integral emergency response system for coal mine water hazard accidents, based on combination weighting, was put forward. Both the empirical evaluation and model validation of the emergency response system for water hazard accidents were carried out by taking five coal mines attached to Henan Coking Coal Group as research objects. The findings suggest that the effectiveness of the emergency response system for water hazard accidents in the Guhanshan Coal Mine and the Zhongmachun Coal Mine is rated as “average”, while those in the Jiulishan Coal Mine, Zhaogu No. 1 Coal Mine, and Zhaogu No. 2 Coal Mine are graded as “good”. This result is consistent with the actual situation, which verifies the capacity of the proposed TOPSIS model to evaluate the emergency response system scientifically and efficiently for coal mine water hazard accidents. This study not only offers new ideas for how to enhance the comprehensive emergency response capability of coal mines with respect to water hazard accidents, but also provides support for making decisions concerning the upgrading of the emergency response capacity of coal mines. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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23 pages, 20895 KiB

Open AccessArticle

Numerical Simulation Analysis of Acoustic Emission Characteristics during the Drilling Pressure Relief Process in Coal Seams under Different Influencing Factors

by Ji Ma, Jiashuo Li, Shuai Zhang, Shengtao Yang, Xiaohang Dong and Dongsheng Liu

Processes 2023, 11(12), 3277; https://doi.org/10.3390/pr11123277 - 23 Nov 2023

Viewed by 588

Abstract

Drilling pressure relief is a widely recognized and applied key technique to reduce the risk of rock burst occurrence, and its field-applied effects are also obvious. In this paper, the values of micro parameters required for discrete element method (DEM) simulations were first [...] Read more.

Drilling pressure relief is a widely recognized and applied key technique to reduce the risk of rock burst occurrence, and its field-applied effects are also obvious. In this paper, the values of micro parameters required for discrete element method (DEM) simulations were first determined through indoor experiments and parameter calibration. Then, drilling pressure relief numerical simulations were conducted with different drilling diameters, drilling angles, and drilling depths. The results show that as the depth and diameter of the borehole increase, the peak strength of the coal sample first rapidly decreases, and then slowly decreases. The 30 mm depth and 14 mm diameter of the borehole are, respectively, the critical thresholds for the transition of the peak strength decrease rate; as the drilling angle increases, the peak strength of the coal sample first rapidly decreases and then increases, and the drilling angle of 25° is the critical threshold for the peak strength transformation. At the same time, the type of coal sample failure also changes from conjugate shear fracture to single slope shear fracture with the increase of three drilling parameters; shear and tensile cracks are the main types of micro fractures in coal samples. The research results are of great significance for improving the pressure relief plan of coal seam drilling and preventing and controlling rock burst disasters. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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15 pages, 7699 KiB

Open AccessArticle

Study on the Spatiotemporal Dynamic Evolution Law of a Deep Thick Hard Roof and Coal Seam

by Zhigang Zhang, Linchao Dai, Haitao Sun, Yanbao Liu, Huiming Yang, Rifu Li and Yi Zhang

Processes 2023, 11(11), 3173; https://doi.org/10.3390/pr11113173 - 07 Nov 2023

Viewed by 525

Abstract

Underground mining in coal mines causes strong disturbance to geological structures and releases a large amount of elastic strain energy. When the roof is a hard and thick rock layer, it is easy to cause dynamic disasters such as rock burst. To analyze [...] Read more.

Underground mining in coal mines causes strong disturbance to geological structures and releases a large amount of elastic strain energy. When the roof is a hard and thick rock layer, it is easy to cause dynamic disasters such as rock burst. To analyze the impact of a deep thick and hard roof fracture on the safe mining of thick coal seams, this paper studied the dynamic evolution process of the stress field, displacement field, energy field, and plastic zone of the coal seam and overlying strata during the mining process using FLAC3D numerical simulation. The results show that as the working face continues to be mined, the concentrated stress in the overlying strata first increases and then decreases, and the support pressure in front of the working face continues to increase. When it advances to 100 m, collapse occurs, and the stress increases sharply; the bottom plate undergoes plastic failure, resulting in floor heave. The overlying strata mass in the top plate exhibits downward vertical displacement, while the rock mass in the bottom plate exhibits upward vertical displacement, with a maximum subsidence of 4.51 m; energy concentration areas are generated around the working face roadway, forming an inverted “U” shape. When collapse occurs, the energy density decreases slightly; the direction of the plastic zone changes from “saddle shaped” to complete failure of the upper rock layer, and the overlying strata is mainly shear failure, which expands with the increase in mining distance. The research results have important practical significance for guiding the safe mining of deep thick and hard roof working faces. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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25 pages, 18946 KiB

Open AccessArticle

Study of Overlying Rock Structure and Intensive Pressure Control Technology of Island Longwall Panel in Extra-Thick Coal Seams

by Yaochuang Wang, Pengkun Chen and Shen Wang

Processes 2023, 11(11), 3083; https://doi.org/10.3390/pr11113083 - 26 Oct 2023

Cited by 1 | Viewed by 614

Abstract

In response to the severe occurrence of mining pressure in the fully mechanized top coal caving face of the extra-thick coal seam and the problem of strong rock pressure caused by the remaining coal pillars in the mining area on the isolated island [...] Read more.

In response to the severe occurrence of mining pressure in the fully mechanized top coal caving face of the extra-thick coal seam and the problem of strong rock pressure caused by the remaining coal pillars in the mining area on the isolated island fully mechanized top coal caving face, taking the 8102 isolated island working face of Tongxin Coal Mine as the background and by using methods such as on-site measurement and numerical simulation experiments, the characteristics of roof mining in the island longwall panel of extra-thick coal seams were analyzed. Establishing a mechanical model for the mining stress and overlying rock stress arch of an isolated working face, the mechanical characteristics of the isolated working face under special conditions were obtained. The results show that the longwall panel no. 8102 has an asymmetric long-arm T-shaped covering layer structure before mining and a C-shaped covering rock structure during mining, which will exacerbate the degree of mining pressure manifestation in the working face. Directional high-pressure hydraulic fracturing was implemented in the gob of longwall panel no. 8102, and the pressure reduction effect of the advance support section of the gob was obvious, ensuring the safety of the working face. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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14 pages, 4873 KiB

Open AccessArticle

Study on Performance Optimization of Water-Rich Grouting Materials Based on Response Surface Methodology

by Xiaoping Li, Guoping Han, Yong Wang, Jie Xu, Jie Du, Bo Yang, Min Zhang, Tao Li and Bo Li

Processes 2023, 11(9), 2789; https://doi.org/10.3390/pr11092789 - 19 Sep 2023

Viewed by 617

Abstract

The quality of borehole sealing is a key factor affecting the efficiency of gas production. A new water-rich grouting material (RW) with composite coagulant and other additives was prepared in this study to overcome the disadvantages of long setting time and low stone [...] Read more.

The quality of borehole sealing is a key factor affecting the efficiency of gas production. A new water-rich grouting material (RW) with composite coagulant and other additives was prepared in this study to overcome the disadvantages of long setting time and low stone rate of traditional cement materials. When the coagulants A is 4 g and coagulants B is 2 g, the setting time of RW material was reduced by 60.85% and 50.62%, which significantly shortened the setting time of the RW material, respectively. Based on the orthogonal method, 29 groups of comparative experiments were designed to investigate the interaction mechanism between different additives on the performance index of RW, including setting time, water secretion rate, and compressive strength. Quadratic regression equations were fitted using the response surface method. All the correlation coefficients R² of each response model were greater than 0.97, R² and R²_adj were less than 0.2 through variance analysis, indicating a high correlation between the actual and prediction results. The water–cement ratio had the most significant effect among all factors on setting time, water secretion rate, and compressive strength of the RW material. The scanning electron microscope (SEM) was used to compared the micromorphological characteristics of RW and conventional Portland cement material (PC). The results showed that the hydration products of RW were mostly smack ettringite, calcium silicate hydrate gel, and calcium hydroxide, which interweaved with each other to form a network structure that was denser than the PC material. Furthermore, the interface bonding degree between RW and injected coal was tighter than that of PC, without obvious cracks at the slurry–coal interface. The results indicate that the addition of composite coagulant can significantly accelerate the hydration process of RW material and also enhance the interface strength of injected coal, which is conducive to improving the grouting quality and sealing effect of the extraction borehole. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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15 pages, 5295 KiB

Open AccessArticle

Research on the Positioning Accuracy of the Cutting Head of a Tunneling Machine Based on Ultra-Wideband Positioning Technology

by Haiyan Ma, Hongkai Zhang, Kunlin Yang, Yingjie Hu, Zeyu Yang and Nianjie Ma

Processes 2023, 11(9), 2534; https://doi.org/10.3390/pr11092534 - 24 Aug 2023

Viewed by 638

Abstract

Directed at the problems of low positioning accuracy and irregular section forming of cutting heads of road header in coal mine production sites, a new cutting head positioning system based on ultra-wideband positioning technology is proposed based on the cutting head motion model [...] Read more.

Directed at the problems of low positioning accuracy and irregular section forming of cutting heads of road header in coal mine production sites, a new cutting head positioning system based on ultra-wideband positioning technology is proposed based on the cutting head motion model and the working principle of ultra-wideband positioning technology, which verifies the anti-interference and the accuracy of its positioning. Combined with the simulation experiment under on-site working conditions, the influence degree of three typical influencing factors on positioning accuracy was obtained, and the accuracy optimization of the ultra-wideband positioning system was guided. Through the dynamic solution experiment, the positioning accuracy of the system is measured, and the results are verified based on the positioning system solution accuracy evaluation standard. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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22 pages, 10171 KiB

Open AccessArticle

Carbon Dioxide Prevents Oxygen Adsorption at Low-Temperature Oxidation Stage of Low-Rank Coal: Laboratory Study and Molecular Simulation

by Gang Cheng, Haiyan Wang, Bo Tan and Shuhui Fu

Processes 2023, 11(8), 2504; https://doi.org/10.3390/pr11082504 - 20 Aug 2023

Viewed by 893

Abstract

Carbon dioxide (CO₂) is widely used in the prevention and control of spontaneous coal combustion. In this manuscript, three low-rank coals with different metamorphic degrees were selected as the research objects. The temperature-programmed experiments, in situ infrared cooling experiments, simulation of [...] Read more.

Carbon dioxide (CO₂) is widely used in the prevention and control of spontaneous coal combustion. In this manuscript, three low-rank coals with different metamorphic degrees were selected as the research objects. The temperature-programmed experiments, in situ infrared cooling experiments, simulation of the competitive adsorption of CO₂ and oxygen (O₂) in coal pores, and simulation study of the CO₂ inhibition of the coal oxygen composite reaction were used to obtain the role and effect of CO₂ in preventing oxygen adsorption in coal at the low-temperature oxidation stage. It was concluded that CO₂ can displace the O₂ near the pore wall to physically prevent the adsorption of O₂. Through the changing law of heating rate and a kinetics analysis, it was found that CO₂ can increase its activation energy by 5.3–108.3% during the slow heating stage of coal and reduce its heat rate. At around 120 °C, coal loses the protective effect of CO₂. From the changes in functional groups, it can be seen that when coal was cooled in the CO₂ atmosphere, mainly pyrolysis and condensation reactions occurred due to the lack of O₂. In addition, CO₂ can also inhibit the chain reaction of the chemical adsorption of oxygen in coal. This work provides a theoretical basis for CO₂ prevention and the control of spontaneous coal combustion. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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14 pages, 278 KiB

Open AccessArticle

Research on the Evaluation of Emergency Management Synergy Capability of Coal Mines Based on the Entropy Weight Matter-Element Extension Model

by Chaolun Sun, Yu Hao, Jianping Wei and Lijun Zhang

Processes 2023, 11(8), 2492; https://doi.org/10.3390/pr11082492 - 19 Aug 2023

Cited by 1 | Viewed by 657

Abstract

Emergency management synergy capability is not only a “touchstone” to measure the operation effect of the emergency system of coal mine enterprises, it is an important symbol to reflect its level. In order to improve the level of emergency management in coal mines [...] Read more.

Emergency management synergy capability is not only a “touchstone” to measure the operation effect of the emergency system of coal mine enterprises, it is an important symbol to reflect its level. In order to improve the level of emergency management in coal mines based on the PPRR theory of crisis management cycle, in this paper a hierarchical evaluation index system is constructed based on the emergency management process. A quantitative evaluation model of emergency synergy capacity is proposes based on the entropy–weighted elemental topology method to conduct evaluation and model validation for the case of J coal mine in Henan Province. The results show that the overall evaluation of the emergency management synergy capability of J Coal Mine is at a “good” level, with the emergency prevention synergy capability, emergency preparedness synergy capability, and recovery and reconstruction synergy capability at a “good” level and the emergency response synergy capability is at a “average” level. This indicates that the evaluation model is consistent with the current development of coal mining enterprises and has universal applicability. Therefore, this research can provide decision-making support for emergency management synergistic capacity building of coal mining enterprises to enhance the inherent driving force behind the early completion of the dual carbon task in the coal mining industry. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

17 pages, 2982 KiB

Open AccessArticle

Analysis of the Current Status and Hot Technologies of Coal Spontaneous Combustion Warning

by Feiran Wang, Zhansuo Ji, Haiyan Wang, Yue Chen, Tao Wang, Ruoyi Tao, Chang Su and Guchen Niu

Processes 2023, 11(8), 2480; https://doi.org/10.3390/pr11082480 - 18 Aug 2023

Cited by 3 | Viewed by 903

Abstract

Coal spontaneous combustion disasters are one of the most serious types of mine disasters in China at present, posing a huge threat to underground personal safety and coal production operations. In order to prevent and control coal spontaneous combustion hazards and construct an [...] Read more.

Coal spontaneous combustion disasters are one of the most serious types of mine disasters in China at present, posing a huge threat to underground personal safety and coal production operations. In order to prevent and control coal spontaneous combustion hazards and construct an efficient early warning system, this paper presents a review of coal spontaneous combustion early warning based on the Web of Science database search of 583 papers related to coal spontaneous combustion early warning collected from 2002 to 2021, using VOSviewer visualization software. The number of publications and partnerships at the author, institution and country levels are obtained, and the research hotspots in the field of coal spontaneous combustion warning are obtained based on keyword co-occurrence and clustering. The results show that the research results of scholars with a high publication volume have significant influence in the field of coal spontaneous combustion warning and prevention and control, and a more mature camp has been formed among the research authors; a more stable core group of institutions has been formed in the field of coal spontaneous combustion warning; most of the national publications are concentrated in mineral resource-mining countries; the analysis of hot keywords shows that “sign gas warning” and “warning models and technologies” are the key contents of this field. The analysis of hot keywords shows that “sign gas early warning” and “early warning model and technology” are the key contents of this field. The research content of this paper is helpful for researchers to find the latest information on the current research and trends in the field of spontaneous combustion prevention and coal seam monitoring. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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18 pages, 9990 KiB

Open AccessArticle

Preliminary Exploration of the Technology of Coal Reshaping and Replacement Mining of Abandoned Coal in Goafs

by Li Li, Xiao Zhang, Bin Hu and Shun Lei

Processes 2023, 11(8), 2474; https://doi.org/10.3390/pr11082474 - 17 Aug 2023

Cited by 1 | Viewed by 782

Abstract

Recycling of coal resources left behind in goafs and the treatment and utilization of solid waste from mines are topical issues faced by the global coal mining industry at present. With the annual reduction of recoverable reserves of coal resources and the dependence [...] Read more.

Recycling of coal resources left behind in goafs and the treatment and utilization of solid waste from mines are topical issues faced by the global coal mining industry at present. With the annual reduction of recoverable reserves of coal resources and the dependence on coal resources that are difficult to replace, the problems have become increasingly prominent, seriously limiting the development of coal resources and the implementation of environmental protection work. The mutual influence between the strength of filling materials and the size of loose coal in the CRRM process through numerical simulation experiments, laboratory rock mechanics experiments, and on-site large-scale similar simulation material experiments is explored. It is ultimately believed that selecting a filling material with a 20 cm particle size of loose coal and a 90% proportion of loose coal for 7 days can meet the requirements of the CRRM process, and this conclusion has been verified through on-site engineering scale experiments. The scientific problems faced by various links in the process of filling and replacing abandoned coal in goafs were analyzed, and improvement methods were further proposed; the technical system of filling and replacing abandoned coal was improved, and new directions for the efficient and safe recovery of abandoned coal resources worldwide in the future were developed. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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18 pages, 6413 KiB

Open AccessArticle

Study on the Influence Mechanism of Air Leakage on Gas Extraction Effect—A Numerical Case Study of the Coal Mine Site in Anhui

by Han Gao, Feng Du, Xiaoyu Cheng, Jinjie Zhang and Aitao Zhou

Processes 2023, 11(7), 2161; https://doi.org/10.3390/pr11072161 - 19 Jul 2023

Viewed by 751

Abstract

Air leakage in mine gas drainage drilling is a critical factor that affects gas extraction efficiency. It leads to a rapid decline in gas concentration, resulting in lower extraction efficiency and potential secondary disasters. To address this issue, a fully coupled gas–air mixed [...] Read more.

Air leakage in mine gas drainage drilling is a critical factor that affects gas extraction efficiency. It leads to a rapid decline in gas concentration, resulting in lower extraction efficiency and potential secondary disasters. To address this issue, a fully coupled gas–air mixed flow model is established in this study. The model examines the effects of extraction time, different negative pressures, and gas leakage on gas concentration. Additionally, it reveals the mechanism of air leakage around gas drainage boreholes. The simulation data are then compared with field gas drainage monitoring data to verify the reliability of the model. This verification serves as a basis for extraction regulation and control. The results demonstrate that during the later stages of extraction, the negative pressure decreases, causing a decline in gas concentration. Moreover, higher negative pressure leads to increased air inflow into the borehole, thereby reducing gas concentration. Consequently, selecting an appropriate negative pressure is crucial to improve pumping efficiency. The research findings hold significant guidance in achieving efficient gas mining. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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14 pages, 7678 KiB

Open AccessArticle

The Influence of High-Pressure Water Jet Cutting Parameters on the Relief of Pressure around the Coal Slot

by Zuo Sun, Yingjie Liu, Qingjie Qi, Jiamei Chai and Beifang Gu

Processes 2023, 11(7), 2071; https://doi.org/10.3390/pr11072071 - 11 Jul 2023

Viewed by 663

Abstract

This research aims to investigate the impact of high-pressure water jet cutting parameters on pressure alleviation around the coal slot. A numerical model of high-pressure water jet cutting coal was developed using FLAC^3D software, allowing for a detailed study of how each [...] Read more.

This research aims to investigate the impact of high-pressure water jet cutting parameters on pressure alleviation around the coal slot. A numerical model of high-pressure water jet cutting coal was developed using FLAC^3D software, allowing for a detailed study of how each cutting parameter affects the pressure relief effect of the slot. The key findings are as follows: as the water jet pressure increases, the plastic area of the coal body around the kerf expands, although the rate of increase diminishes, with the optimal water jet pressure being 30 Mpa. The results suggest that hydraulic slotting measures are particularly beneficial for outburst prevention in high in situ stress coal seams. The pressure relief range exponentially grows with an increase in the kerf depth, signifying that enhancing the kerf depth has a notable effect on improving the hydraulic kerf pressure relief. As the slit width increases, the volume of the slit enlarges, leading to a significant rise in the pressure relief range of the surrounding coal body. Given that an increase in the slit width necessitates an increase in the nozzle outlet diameter and slotting time, the optimal slit width is determined to be 0.2 m. The research concludes that the optimal hydraulic slit spacing is 3 m. This study offers valuable theoretical guidance for high-pressure water jet slotting. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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16 pages, 9188 KiB

Open AccessArticle

Research on Hydraulic Thruster-Enhanced Permeability Technology of Soft Coal Drilling through Strata Based on Packer Sealing Method

by Zhuangzhuang Yao, Zhigang Zhang and Linchao Dai

Processes 2023, 11(7), 1959; https://doi.org/10.3390/pr11071959 - 28 Jun 2023

Viewed by 665

Abstract

According to the characteristics of “Three Soft” outburst coal seams in the Henan area with large gas content, poor air permeability, and extremely difficult extraction, the hydraulic fracturing and punching technology of soft coal with packer tool string sealing method was studied. Xinzheng [...] Read more.

According to the characteristics of “Three Soft” outburst coal seams in the Henan area with large gas content, poor air permeability, and extremely difficult extraction, the hydraulic fracturing and punching technology of soft coal with packer tool string sealing method was studied. Xinzheng Coal Electric Power Company is a coal and gas outburst mine, and the second coal seam is a typical soft outburst coal seam. In 14201, upper bottom drainage roadway, which has a broken top plate, a test of penetration hydraulic pressure thrust-enhanced permeability technology based on packer sealing mode was carried out. The average concentration in the press-punching area was 4.8 times that in the non-press-punching area (to be tested), and the average pure volume of 100 holes in the test area was 42 times that in the untested area. During hydraulic pressure punching in the test area, affected by fracturing disturbance, the concentration and purity of the test area and the adjacent test area significantly increased. The test verifies that the large range of fracturing communication cracks at the same time through the interception hole punching plays a synergic permeability and pressure relief effect, providing a new idea and technical support for the hydraulic permeability increase technology in this area. Full article

(This article belongs to the Special Issue Intelligent Safety Monitoring and Prevention Process in Coal Mines)

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