An improved method for high‐efficiency coal mine methane drainage: Theoretical analysis and field verification

Liu, Qingquan; Zhang, Hongxing; Wang, Chenghao; Shu, Longyong; Ullah, Barkat

doi:10.1002/ese3.248

Cited by 8 publications

(7 citation statements)

References 25 publications

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“…Xue et al and Liu et al thought that there are usually three zones around the borehole after excavation. The three zones, which include elastic strain zone, plastic damage strain zone, and residual stress zone, are corresponding to the strain softening model.…”

Section: Numerical Simulation Of Permeability Model's Application To mentioning

confidence: 99%

Damage‐induced permeability model of coal and its application to gas predrainage in combination of soft coal and hard coal

Zhang

et al. 2019

Energy Science & Engineering

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Coal permeability is a key parameter that affects the drainage of coal bed methane (CBM). Owing to the lower original permeability of coal seams in China, more attention was paid to the study of damage‐induced permeability laws. However, the theory of damage‐induced permeability still needs to be improved. In this paper, the permeability evolution experiments during the complete stress–strain process of coal were carried out firstly. The results are shown that with the increase in axial strain, the coal permeability decreases slowly at first, then increases rapidly, and finally increases slowly or even remains unchanged, and the peak stress point can be regarded as the extreme point of permeability. Then, the equivalent plastic strain was used to describe the damage of coal. Based on the above results, a new damage‐induced permeability model was developed, and the new model can match the experimental data of permeability very well. In addition, solid–gas coupling models of coal were developed based on the new permeability model, and the numerical results show that there is a region of sudden increase in permeability around the borehole where plastic failure occurs, which indicates that the damage‐induced permeability model is reasonable. Finally, the results of numerical simulation of gas predrainage in combination of soft coal and hard coal under different cases were used to optimize the borehole layout of gas predrainage in the field.

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Section: Numerical Simulation Of Permeability Model's Application To mentioning

confidence: 99%

Damage‐induced permeability model of coal and its application to gas predrainage in combination of soft coal and hard coal

Zhang

et al. 2019

Energy Science & Engineering

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“…The N-S equation is a governing equation that describes the fluid in pipelines [27]. It is expressed as 6 Geofluids where ρ is the density of the gas, u is the speed of the gas, p is the pressure of the gas, and η is the viscosity coefficient of the gas. The gas transmission law in the coal seam basically conforms to Darcy's law [28,29], and it can be expressed as…”

Section: Governing Equation Of the Gas Flowmentioning

confidence: 99%

“…In terms of determination of reasonable sealing depth in gas extraction, some researchers studied the problem through theoretical analysis and numerical simulation. For example, the failure mode of in-seam CMM drainage boreholes and the fracture characteristics of the coal surrounding a roadway were analyzed using a viscoelastic plastic model while considering the plastic softening and dilatancy, and the proper sealing depth of an in-seam borehole was studied based on the theoretical findings [6]. A method is proposed to study the roadway geological conditions in the coal seam by monitoring the response of the idle pressure of the hydraulic motor while drilling the boreholes, and using numerical analysis, the reasonable sealing depth should be several meters larger than the stress concentration area, which is indicated in practice by the idle pressure [7,8].…”

Section: Introductionmentioning

confidence: 99%

A New Width Measurement Method of the Stress Relief Zone on Roadway Surrounding Rocks

et al. 2019

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Determining the width of the stress relief zone on roadway surrounding rocks is the premise to optimize drilling borehole effect and increase gas extraction efficiency. In this study, a new width measurement method of the stress relief zone on the roadway surrounding rocks was proposed, which determined the width according to gas pressure attenuation speeds in roadway boreholes at different depths. Then, the variation curve of the gas pressure in boreholes at different depths with the time was gained through a field test. On this basis, laws of the gas pressure attenuation and the gas transmission and loss in boreholes at different depths were explored through a numerical simulation based on COMSOL Multiphysics, thus concluding the stress on roadway surrounding rocks, the distribution of plastic zones, and the stress-permeability relation. The scientificity of the proposed method was illustrated theoretically. Finally, the proposed method was verified by the field test data and numerical simulation results of the gas extraction at different sealing depths. Research results demonstrate that the pressure in boreholes attenuates in the logarithmic function pattern. The attenuation speed decreases with the increase of the drilling depth. The width of the stress relief zone on roadway surrounding rocks in the studied area was determined to be about 11 m according to the proposed method. Both the numerical simulation and the field test of the gas extraction efficiency prove the feasibility and validity of the proposed method in determining the sealing depth of the borehole for the gas extraction. Research conclusions are of important significance to enrich width measurement methods of the stress relief zone on roadway surrounding rocks and to optimize sealing parameters of underground boreholes for gas extraction.

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“…To prevent sand column compaction, the maximum compression of the sand column must be satisfied:εmax=ΔhA−∑δ where ΔhA is the final subsidence of the main roof in metres, KA is the bulking coefficient of the immediate roof, generally taken as 1.30, L1 is the lateral length of the main roof in metres [3,29], a is the width of the roadway in metres, b is the width of the sidewall support in metres, εmax is the maximum permissible compression of the sidewall support in metres, and ∑δ is the compression of the sidewall support through the roof/floor and the auxiliary support, as obtained from field measurement results.…”

Section: Theoretical Analysis Of the Applicability Indexes For Tdcsmentioning

confidence: 99%

“…On this basis, the deformation capacities of the sidewall filler, subject to the limitations of the roadway size and of the coal side, are as follows. The ultimate deformation of the sidewall-support system:Δhf≤hf·(L0+normala+b2)3L0+2normala where L0 is the distribution range of lateral abutment pressure in metres [3,29].…”

Section: Theoretical Analysis Of the Applicability Indexes For Tdcsmentioning

confidence: 99%

Applicability of Yielding–Resisting Sand Column and Three-Dimensional Coordination Support in Stopes

et al. 2019

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In view of the existing problems of stope roadways, which are difficult to maintain under the influence of high ground and mining-induced stresses, the structural characteristics and movement regularities of stopes surrounding rocks were analysed. Through the construction of a three-dimensional mechanical model of the coordination support of a stope, the adaptability index of the support in stope is presented, and its mechanism of operation is expounded. Yielding–resisting sand column (YRSC) sidewall-support technology with satisfactory compressibility and supporting strength was developed. The structure and actual mechanical properties of the YRSC were investigated through laboratory experiments, and the optimum ratio of filling materials was obtained. The good applicability of the load and deformation adaptability index of the three-dimensional coordination support in the stope and YRSC sidewall-support technology were demonstrated in practice at the No. 12306 working face of the Dongda coal mine. It was shown that the designed carrying capacity and compression of the sand columns satisfied the site requirements. The actual stress and deformation of the YRSC exhibited three stages: Slow growth at the initial stage, a large increase in the medium term, and a stable trend at the end. The adaptability index of the three-dimensional coordination support in the stope considers all bearing structure units of the stope as an interconnected whole, and the stability conditions of the stope roadway can be quantitatively described. The supporting effect of the YRSC is remarkable and can be applied to the construction of tunnels, bridge systems and other engineering fields.

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An improved method for high‐efficiency coal mine methane drainage: Theoretical analysis and field verification

Cited by 8 publications

References 25 publications

Damage‐induced permeability model of coal and its application to gas predrainage in combination of soft coal and hard coal

Damage‐induced permeability model of coal and its application to gas predrainage in combination of soft coal and hard coal

A New Width Measurement Method of the Stress Relief Zone on Roadway Surrounding Rocks

Applicability of Yielding–Resisting Sand Column and Three-Dimensional Coordination Support in Stopes

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