Expansion energy of coal gas for the initiation of coal and gas outbursts

Abstract. Large-scale coal and gas outbursts pose a risk of fatal disasters in underground mines. Large-scale outbursts (outburst of coal and rock greater than 500 t) in recent years in China indicate that there is abundant gas in areas of outbursts containing large amounts of potential energy. The adequate sealing properties of the roof and floor of a coal seam are required for local abundant gas around the site of an outburst, but an annular low-permeability zone in a coal seam, which prevents the loss by gas migration through the coal seam itself, is also required. The distribution of coal gas with this annular zone of low permeability is described, and it is proposed that the annular zone of low permeability creates conditions for confining the coal gas. The effect of this low-permeability zone on the gas distribution is analyzed after allowing for simplifications in the model. The results show that the permeability and length of the low-permeability zone have a great impact on the gas distribution, and the permeability is required to be several orders of magnitude less than that of normal coal and enough length is also in demand. A steep gradient of gas pressure in the low-permeability zone and the high-pressure gas in the abundant zone of gas can promote coal mass failure and coal wall deformation, thereby accelerating the coal and gas outburst. The high-pressure gas in abundant zone of gas will lead to a large-scale outburst if an outburst occurs.

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An explanation of large-scale coal and gas outbursts in underground coal mines: the effect of low-permeability zones on abnormally abundant gas

Natural Hazards and Earth System Sciences Discussions ◽

10.5194/nhessd-1-4751-2013 ◽

2013 ◽

Vol 1 (5) ◽

pp. 4751-4775 ◽

Cited By ~ 5

Author(s):

F. H. An ◽

Y. P. Cheng

Keyword(s):

Coal Seam ◽

Large Scale ◽

Gas Pressure ◽

Underground Mines ◽

Low Permeability ◽

Gas Distribution ◽

Coal Gas ◽

Annular Zone ◽

Wall Deformation ◽

Coal And Gas Outbursts

Abstract. Large-scale coal and gas outbursts post a risk of fatal disasters in underground mines. Large-scale outbursts (outburst of coal and rock greater than 500 t) in recent years in China indicate that there is abundant gas in areas of outbursts containing large amounts of potential energy. The adequate sealing properties of the roof and floor of a coal seam are required for local abundant gas around the site of an outburst, but an annular low-permeability zone in a coal seam, which prevents the loss by gas migration through the coal seam itself, is also required. The distribution of coal gas with this annular zone of low permeability is described, and it is proposed that the annular zone of low permeability creates conditions for confining the coal gas. The effect of this low-permeability zone on the gas distribution is analyzed after allowing for simplifications in the model. The results show that the permeability and length of the low-permeability zone have a great impact on the gas distribution. A steep gradient of gas pressure in the low-permeability zone and the high gas pressure in the abundant zone of gas can promote coal mass failure and coal wall deformation, thereby accelerating the coal and gas outburst. The high pressure gas in abundant zone of gas will lead to a large-scale outburst if an outburst occurs.

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The Relationship between Mining-Induced Stress and Coal Gas under an Optimized Support Scheme: A Case Study in the Guanyinshan Coal Mine, China

Geofluids ◽

10.1155/2021/2421398 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Tianjun Zhang ◽

Jiaokun Wu ◽

Yong Chen ◽

Hong Ding ◽

Hongyu Ma ◽

...

Keyword(s):

Gas Pressure ◽

Gas Content ◽

Rock Support ◽

Drill Cuttings ◽

Coal Gas ◽

Gas Desorption ◽

Induced Stress ◽

Coal And Gas Outbursts ◽

Residual Gas ◽

The Relationship

Stress is one of the main factors influencing coal and gas outbursts. The apparent effects of the crustal stress, the structural stress, and the mining-induced stress increase as the depth of mining increases. At present, there have been few studies of the relationship between the comprehensive analyses of the crustal stress, mining-induced stress, and coal gas. The in situ measurement of the relationship between stress-related behaviors and coal gas under the influence of mining was conducted through experimental analysis of surrounding rock support and coal and gas outburst control and optimization of surrounding rock support materials and system construction. The results showed that the mining-induced stress first increased to a peak value, then gradually decreased, and tended to stabilize as the footage progresses. Stress appears at 96 m ahead due to mining; after 57 m of advancing, there is a large increase until it passes through this area. The stress in front of the working face increases linearly, and the increase range is obviously larger than that of the coal body in a certain range on both sides. The support anchoring force gradually decreased and tended to be stable after rapidly increasing to a maximum value. The deep displacement of the roof increased linearly and tended to be stable after reaching an accumulated displacement which can reach 16-28 mm. The residual gas pressure in front of mining operations decreased rapidly, and beyond 15 m on each side of the roadway, it decreased significantly. The residual gas pressure and gas content were consistent with the gas desorption index of drill cuttings due to the influences of gas predrainage and mining. The stress along the direction of the roadway and the residual gas content, the residual gas pressure, and the gas desorption index of drill cuttings conform to the logarithmic functional relationship. The research results provide a basis for the comprehensive prevention and control of coal and gas outbursts from multiple angles considering stress, coal, and gas.

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The Effect of a Tectonic Stress Field on Coal and Gas Outbursts

The Scientific World JOURNAL ◽

10.1155/2014/813063 ◽

2014 ◽

Vol 2014 ◽

pp. 1-10 ◽

Cited By ~ 6

Author(s):

Fenghua An ◽

Yuanping Cheng

Keyword(s):

Potential Energy ◽

Elastic Energy ◽

Tectonic Stress ◽

Coal Mass ◽

Stress Conditions ◽

Coal Gas ◽

Adsorbed Gas ◽

Field Practice ◽

Ground Stress ◽

Coal And Gas Outbursts

Coal and gas outbursts have always been a serious threat to the safe and efficient mining of coal resources. Ground stress (especially the tectonic stress) has a notable effect on the occurrence and distribution of outbursts in the field practice. A numerical model considering the effect of coal gas was established to analyze the outburst danger from the perspective of stress conditions. To evaluate the outburst tendency, the potential energy of yielded coal mass accumulated during an outburst initiation was studied. The results showed that the gas pressure and the strength reduction from the adsorbed gas aggravated the coal mass failure and the ground stress altered by tectonics would affect the plastic zone distribution. To demonstrate the outburst tendency, the ratio of potential energy for the outburst initiation and the energy consumption was used. Increase of coal gas and tectonic stress could enhance the potential energy accumulation ratio, meaning larger outburst tendency. The component of potential energy for outburst initiation indicated that the proportion of elastic energy was increased due to tectonic stress. The elastic energy increase is deduced as the cause for a greater outburst danger in a tectonic area from the perspective of stress conditions.

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