Determination of critical value of an outburst risk prediction index of working face in a coal roadway based on initial gas emission from a borehole and its application: A case study

Tang, Jun; Wang, Chaojie; Chen, Yu-Jia; Li, Xiaowei; Yang, Dingding; Liu, Jie

doi:10.1016/j.fuel.2020.117229

Cited by 25 publications

(13 citation statements)

References 24 publications

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“…As one of the most serious disasters in coal mines, the prediction of coal and gas outburst is particularly important [1][2][3]. The gas desorption index of drilling cuttings is the most widely used to predict coal and gas outbursts [4][5][6][7]. The key to the accuracy of the gas desorption index of drilling cuttings is to establish a suitable mathematical model of coal gas emission, especially in the initial stage [8].…”

Section: Introductionmentioning

confidence: 99%

Gas emission characteristics of tectonic coal in the initial stage: Application for coal and gas outburst prediction

Zhang

Huo

Shu

et al. 2022

Preprint

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Coal and gas outburst is one of the most disasters threating the safety and production of coal mines. Accurate description of the gas emission characteristics in the initial stage for tectonic coal is the key to improving the prediction accuracy of coal and gas outburst. In this work, the gas emission test of original and tectonic coal particles under the constant temperature was carried out. The optimal mathematical model suitable for the gas emission in the initial stage was then analyzed. Moreover, the time influencing factors of the optimal mathematical model were discussed. The research results show that cumulative gas desorption amount during 0-7 minute for tectonic coal is 1.28-1.41 times as much as that for original coal. The applicability of current mathematical model for describing the gas emission characteristics of tectonic coal in the initial stage has limitations. Five typical mathematical expressions are selected and compared to fit gas emission curve in the initial stage. Considering the sensitivity of parameters in outburst prediction, the optimal mathematical model was obtained. In addition, the time factor has a great influence on the application effect of mathematical model in coal and gas outburst prediction. For current mathematical model, the errors of tectonic coal are all negative. The greater the gas pressure and the later the measurement time, the greater the error. The errors in 1~6 min are -0.46%~-1.78%, and the errors in 2~7 min are -1.00%~-3.86%, which is not conducive to the safety of outburst prediction. Therefore, the optimal mathematical model has the possibility to overcome the limitations of current mathematical model. The research results provide a theoretical basis for the correction of coal and gas outburst prediction indicators.

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Section: Introductionmentioning

confidence: 99%

Gas emission characteristics of tectonic coal in the initial stage: Application for coal and gas outburst prediction

Zhang

Huo

Shu

et al. 2022

Preprint

View full text Add to dashboard Cite

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“…The coal structure directly affects gas accumulation. Hence, there are a large number of coal and gas outburst mines in the northern basin. , On the other hand, broken coal is not conducive to the stability of drilling wellbore, and artificial channels after hydraulic fracturing cannot communicate effectively, which makes it difficult to form a large-scale pressure drop funnel in the CBM well zone, resulting in low CBM production generally …”

Section: Resultsmentioning

confidence: 99%

“…Compared with primary coal, the tectonic coal seam with structural deformation has low strength, poor gas permeability, high gas adsorption, fast desorption, and increases risk of coal and gas outburst, which is extremely unfavorable for coal mining. 40 Inspection drilling is carried out in the roadway to measure the relevant parameters to determine whether the roadway has outburst hazards. By analyzing the characteristics of drilling cuttings in the borehole, the coal structure tens of meters or even hundreds of meters in front of the coal head can be predicted.…”

Section: Introductionmentioning

confidence: 99%

“…Xinyuan Mine is a coal and gas outburst mine, which faces the challenge of outburst control during the excavation roadway or working face. Compared with primary coal, the tectonic coal seam with structural deformation has low strength, poor gas permeability, high gas adsorption, fast desorption, and increases risk of coal and gas outburst, which is extremely unfavorable for coal mining . Inspection drilling is carried out in the roadway to measure the relevant parameters to determine whether the roadway has outburst hazards.…”

Section: Introductionmentioning

confidence: 99%

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Coal Structure Characteristics in the Northern Qinshui Basin and Their Discrimination Method Based on the Particle Size of Drilling Cuttings

et al. 2022

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Coal structure, including primary coal, cataclastic coal, granulated coal, and mylonitized coal, is one of the key factors controlling coal and gas outburst, and it also determines the efficiency of coalbed methane (CBM) extraction. Therefore, it is significant to identify the characteristics of coal structures and to predict them in advance. In this work, the spatial distribution, mechanical properties, and microscopic morphology of the four coal structures from the No. 3 coal seam of the Xinyuan Mine in the northern part of the Qinshui Basin were investigated through the in situ observation in the roadway, the hardness coefficient ( f ) test, and the scanning electron microscope analysis. Moreover, the drilling cuttings from the gas pressure releasing holes were sampled and sieved, and then, the correspondence between different coal structures and the particle size of the cuttings was analyzed quantitatively based on the Rosin–Rammler model. The result shows that the spatial distribution of the coal structure has strong heterogeneity in the vertical and lateral directions. The f value decreases successively with the increase in coal structure deformation, which indicate that f can directly characterize the coal structure. Furthermore, the relations between f and drilling cutting average particle size ( d 0 ), crushability indicator ( n ), crushing degree index (λ), and the median diameter ( d 50 ) were established. Specifically, the coal deformation degree is positively correlated with the mass fraction of large particles in the cuttings under the same drilling parameters. Overall, as f increases, d 0 and d 50 decrease, and n and λ increase. However, parameters d 0 , d 50 , and λ of granulated coal are inconsistent with other coal structures, and mylonitized coal is inconsistent with other coal structures in n , as a result of the coal structure broken characteristics itself and the difference in the stress state between the coal and the drill bit during the rock breaking process. Ultimately, the coal structures determined by the surface CBM well logging curve and the cuttings particle size method were compared, and they have a high degree of coincidence in the distinction between primary coal and tectonic coal.

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“…The coal and gas outburst, which is influenced by many factors, such as in situ stress, gas pressure, and coal’s physical characteristics, is a very complex dynamic phenomenon occurring in coal mining. − Once a coal and gas outburst occurs, a large amount of coal with gas is rapidly ejected to the working tunnel, resulting in mining equipment damage and casualties. − Up to now, coal and gas outbursts still happen sometimes in coal mining, which pose a great challenge and threat to the coal safety mining. The mechanism research on coal and gas outbursts is generally regarded as a vital part of outburst prevention and control.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Coal and Gas Outbursts under Different In Situ Stresses and Gas Pressures and the Physical Characteristics of Coal

et al. 2021

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The coal and gas outbursts are recognized as a worldwide difficulty, and there is still ample research space in this field, especially on the mechanical mechanism of outbursts. The main purpose of this paper is to attempt to reveal the outburst mechanism as fully as possible from the point of view of mechanics. In this paper, a mechanical model on coal and gas outbursts including the governing equations of gas desorption–seepage, the stress state in the coal sample, and the criteria of coal sample failure and outburst evolution is put forward according to the porous media seepage theory and elastic theory. Based on the proposed model, the variation and distribution of the gas state and stress state in the coal sample in the outburst are analyzed quantitatively and a series of detailed discussions are conducted in terms of the in-situ stress, gas pressure, and the physical characteristics of coal in outbursts. The results of theoretical analysis and numerical simulation show that the stress concentration in the front of the outburst cavity is the main reason for the failure of the coal sample in this area, and then, the drag force caused by gas flow provides energy for the movement of the crushed coal sample, which leads to the outburst cavity expansion and the increase of stress concentration factor. The end of the outburst is because the gas velocity is less than the threshold friction velocity of the crushed coal sample. Additionally, the outburst strength increases with the increase of the vertical in-situ stress and initial gas pressure and decreases with the increase of the internal friction angle and cohesion of coal.

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Determination of critical value of an outburst risk prediction index of working face in a coal roadway based on initial gas emission from a borehole and its application: A case study

Cited by 25 publications

References 24 publications

Gas emission characteristics of tectonic coal in the initial stage: Application for coal and gas outburst prediction

Gas emission characteristics of tectonic coal in the initial stage: Application for coal and gas outburst prediction

Coal Structure Characteristics in the Northern Qinshui Basin and Their Discrimination Method Based on the Particle Size of Drilling Cuttings

Numerical Investigation of Coal and Gas Outbursts under Different In Situ Stresses and Gas Pressures and the Physical Characteristics of Coal

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