Extending the protection range in protective seam mining under the influence of gas drainage

Wang, L.; Chen, X.; Wang, Z.; Xu, Shuai; Xu, Qian

doi:10.17159/2411-9717/17/115/2020

Cited by 3 publications

(3 citation statements)

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“…At the same time, cracks develop. With the increase in the interbedded spacing, fractures develop in the gradually weakened floor rock [13][14][15].…”

Section: Influence Of Mining On Underlying Stratamentioning

confidence: 99%

Study on Overburden Movement and Fissure Evolution Law of Protective Layer Mining in Shallow Coal Seam

Liu

2022

Energies

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This study aims to effectively solve the problem of the destruction of the coal roof and floor overlying rock after mining the protective layer, and determines whether the gas in the protected layer can be effectively released. We do this based on the engineering background of the Weng’an Coal Mine; research and analysis of the movement of the roof and floor overlying rocks; the evolution of cracks and the pressure relief characteristics of the protected layer after mining the protective layer; and through theoretical analysis and similar simulation experiments. Through numerical simulation, it was found that the protected layer was depressurized due to the mining of the protective layer, and the decompression rate of the protected layer was 0.2–0.8. In addition, the overall expansion rate of the protected layer was greater than the requirements of the “Detailed Rules for Prevention and Control of Coal and Gas Outbursts” for coal mines, and the investigation of the residual gas pressure and content of the protected layer revealed that the protected coal seam had been mined in the upper protective layer coal face. The gas pressure dropped to 50.7% of the original coal seam gas pressure, the rate of decrease was 49.3%, the residual gas content dropped by 68.67%, and the gas concentration in the return airway was 0.31% on average, meeting the national regulations that require its value to be less than or equal to 1%. The study comprehensively demonstrates that mining of the protective layer is beneficial to the release of gas from the protected layer, and provides a practical reference for coal and gas outbursts in mines.

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“…At the same time, cracks develop. With the increase in the interbedded spacing, fractures develop in the gradually weakened floor rock [13][14][15].…”

Section: Influence Of Mining On Underlying Stratamentioning

confidence: 99%

Study on Overburden Movement and Fissure Evolution Law of Protective Layer Mining in Shallow Coal Seam

Liu

2022

Energies

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“…e protective coal seam mining has been recognized as one of the most efficient mining methods in order to minimize or even prevent the coal and gas burst hazards and hence it has been investigated extensively globally. Wang et al [4] confirmed that the protective coal seam mining is the most economical efficient method to prevent the coal and gas burst through analytical and field testing research. Wang et al [5] pointed out that the coal seam gas predrainage is the most efficient way to eliminate the risk associated with coal and gas burst.…”

Section: Introductionmentioning

confidence: 98%

Stress Distribution and Gas Concentration Evolution during Protective Coal Seam Mining

Niu

Shi

Zhang

et al. 2021

Advances in Civil Engineering

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Coal and gas burst is one of the significant and catastrophic hazards in underground longwall operations. To date, the protective coal seam mining has been recognized as the most effective mining method for minimizing or even avoiding the effect of the coal and gas burst. In this paper, numerical modelling and field test were carried out for the longwall operation in Qidong Coal Mine in order to investigate the induced stress and coal seam gas drainage performance in the protected coal seam after the complete extraction of the protective coal seam. It was found that four stress zones can be classified in the protected coal seam being the original stress zone, stress concentration zone, stress relief zone, and recompaction zone. In addition, the monitoring data of gas concentration and volume change in the field agree well with the numerical modelling results.

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“…4 coal seam were more optimal than in the shallow zone of the coal seam, and that, with the continuation of mining activities, the decompression area was observed to be moving in the mining direction; moreover, they noted that the permeability of the original decompression area was gradually reduced due to the restoration of geostatic stress. Wang et al [19] and Fan et al [20] concluded that, although the effective protection range of protected seam mining is often smaller than the mining area where the coal seam is being protected, through the rational arrangement of pressure relief extraction drill holes, the extraction of coal seam gas from the protected coal seam can effectively expand the protection range and enhance the protection efficiency. Xie et al [21] analyzed the influencing factors that affect the evolution of secondary fissures in the mining of the upper protected seam.…”

Section: Introductionmentioning

confidence: 99%

Analyzing the Optimization of Unloading Gas Extraction Drilling Arrangement Based on Stress Distribution in the Protected Layer

Xiao,

Chen,

et al. 2024

Sustainability

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In the process of protected seam mining, the reduction in stress and the enhancement of the gas mobility that affects the protected seam are crucial manifestations of the protection effect. Taking the working face of E8-32010 and the upper D5-6 coal seam of the Six Mines of Ping Coal Company Limited as the study object, the research method combining theoretical analysis, numerical simulation, and a field test was adopted. In combination with the actual production, we adopted the stress distribution law pertaining to the coal body of the protected seam under the condition of 2.2 m mining height. When the length of the tendency of the working face mining is under the condition of 2.2 m mining height and when the working face mining inclination lengths are 120 m, 160 m, 200 m, 220 m, 240 m, and 280 m, the stress distribution law that regulates the coal body of the protected seam is analyzed, and, based on the stress distribution law, the unpressurized extraction drilling holes are designed, and the effect of the coal body stress at the final hole position of the unpressurized extraction drilling holes on the efficiency of unpressurized extraction is determined through on−site extracting data. The research results indicate the following: (1) as the tendency length of the working face increases, the degree and range of pressure unloading that affects the protected layer are increasing, the stress increase in the deep D5-6 seam is larger than that of the shallow D5-6 seam, and the tendency direction can be divided into the stress elevation area, pressure unloading area, and stress elevation area from the shallow zone to the deep zone. Moreover, the minimum stresses in the pressure unloading area are 7.80 MPa, 6.42 MPa, 5.59 MPa, 5.59 MPa, 5.42 MPa, 5.30 MPa, and 5.21 MPa, and the minimum stress is less than 60% of the original stress; (2) the vertical stresses at the final locations of the No. 1, No. 2, and No. 3 drill holes after the protective layer is mined are 16.42 MPa, 10.74 MPa, and 6.72 MPa, respectively, and the pure amount of gas extracted from the unpressurized extracting drill holes has increased immensely; the higher the rate of unloading, the greater the increase, and, the more the unpressurized extracting drill holes are extracted, the greater the increase. The higher the unloading rate, the greater the increase: 19.77–21.31 times, 41.62–41.68 times, and 68.68–74.66 times the pure amount of gas extracted from the corresponding pre−pumping holes; (3) the No. 3 depressurized extraction borehole is 261.02–281.04 times, 191.77–205.55 times, and 138.43–148.18 times higher than the No. 1, No. 2, and No. 3 pre−pressurized extraction boreholes, respectively, and 6.09–7.14 times and 2.28–2.49 times higher than the No. 1 and No. 2 depressurized extraction boreholes, respectively. The research results can not only provide a theoretical basis for verifying the protection effect of the protected layer but also a scientific rationale for the layout of the unpressurized extraction drill holes.

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Extending the protection range in protective seam mining under the influence of gas drainage

Cited by 3 publications

References 0 publications

Study on Overburden Movement and Fissure Evolution Law of Protective Layer Mining in Shallow Coal Seam

Study on Overburden Movement and Fissure Evolution Law of Protective Layer Mining in Shallow Coal Seam

Stress Distribution and Gas Concentration Evolution during Protective Coal Seam Mining

Analyzing the Optimization of Unloading Gas Extraction Drilling Arrangement Based on Stress Distribution in the Protected Layer

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