Quantitative evaluation of stress-relief and permeability-increasing effects of overlying coal seams for coal mine methane drainage in Wulan coal mine

Xue, Yi; Gao, Feng; Gao, Yanan; Cheng, Hongmei; Liu, Yingke; Hou, Peng; Teng, Teng

doi:10.1016/j.jngse.2016.04.029

Cited by 46 publications

(23 citation statements)

References 32 publications

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“…15,16 According to the Mohr-coulomb failure criterion, the loading stress path and unloading stress path both can make the coal be damaged. 17,18 For the loading stress path, Yang et al, 19 Wang et al, 20,21 and Xue et al [22][23][24][25] experimentally studied the change law of damage-induced permeability due to loading stress in the process of the complete stress-strain of coal samples. For the unloading stress path, Yin et al, [26][27][28][29] Xu et al, 30 and Zhang et al 31 carried out a large number of experiments to analyze the influencing factors such as style of loading stress path, speed of unloading stress, and cyclic unloading stress on coal permeability.…”

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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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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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“…According to Darcy's law, the permeability of raw coal was calculated according to the reference. 25,26 where K is the permeability of the coal samples (mD), u is the absolute viscosity of gas, (Pa·s), Q is the gas permeation rate (cm 3 /s), P a is the atmospheric pressure (Pa), L is the length of the coal sample (cm), A is the cross-sectional area of coal sample (cm 2 ), P 1 is the gas pressure of the inlet pipe (Pa), and P 2 is the gas pressure of the outlet pipe (Pa). In this experiment, only the evolution characteristics of the permeability of RC-1 were analyzed since the coal samples had similar permeability variations.…”

Section: Analysis Of the Permeability Curve Of Coal Samplesmentioning

confidence: 99%

Experimental study on evolution in the characteristics of permeability, deformation, and energy of coal containing gas under triaxial cyclic loading‐unloading

Chu

Sun

Zhang

2019

Energy Science & Engineering

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To further more deeply understand the influence of cyclic loading‐unloading on coal seams during mining and reduce the rock burst and coal and gas outburst disasters and ensure safety during coal mining, triaxial cyclic loading‐unloading tests were performed on coal samples. The permeability recovery rate, residual deformation, and dissipated energy ratio were defined to analyze the evolution in the characteristics of permeability, deformation, and energy observed during the triaxial cyclic loading‐unloading test. The results show as following: (a) The absolute permeability recovery rate first gradually decreases and then increases before failure, while the relative permeability recovery rate decreases sharply during the compaction stage, remains stable during the elastic phase, and gradually increases before failure; (b) The cumulative residual deformation increases with increase number of cyclic loading‐unloading, while relative residual deformation first decreases gradually, then stabilities, and then rises sharply before failure; (c) With increases in deviatoric stress, the total energy of coal samples increased as an exponential function. The dissipated energy ratio gradually decreased in the initial stages of cyclic loading‐unloading, then tended to stabilize in the elastic stage and then increase gradually before failure. This study provides precursor conditions for the early warning of rock burst and coal and gas outburst disasters, which has great importance for reducing coal mine dynamics disasters.

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“…In view of the highly consistent mechanical properties, the homogeneity and the reproducibility of the coal-like material developed in this study; the synthetic material could be used in place of natural coal sample to study the triaxial and rheological mechanical properties of soft tectonically deformed coal. The relevant experimental results will help guide the design of roadway support for soft coal seams, the stability control of the gas drainage borehole [49,50] and the prediction of coal and gas delayed outburst.…”

Section: Application Prospects Of Solid-gas Coupling Coal-like Materialsmentioning

confidence: 99%

Experimental Development of Coal-Like Material with Solid-Gas Coupling for Quantitative Simulation Tests of Coal and Gas Outburst Occurred in Soft Coal Seams

Wang

Xie

et al. 2019

Processes

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Solid-gas coupling coal-like materials are essential for simulating coal and gas outbursts and the long-term safety study of CO2 sequestration in coal. However, reported materials still differ substantially from natural coal in mechanical, deformation and gaseous properties; the latter two aspects are common not considered. There is a lack of a definite and quantitative preparation method of coal-like materials with high similarity for future reference. Here, 25 groups of raw material ratios were designed in the orthogonal experiment using uniaxial compression, shearing and adsorption/desorption tests. Experiment results indicated that the coal-like materials were highly similar to soft coals in properties mentioned above. And range analysis revealed the key influencing factors of each mechanical index. The gypsum/petrolatum ratio controls the density, compressive strength, elastic modulus, cohesion and deformation characteristic. The coarse/fine coal powder (1–2 and 0–0.5 mm) controls the internal friction angle and is the secondary controlling factor for compressive strength and elastic modulus. The effect of coal particle size on the sample strength was studied using scanning electron microscope (SEM). When the gypsum/petrolatum ratio increased, the deformation characteristics changed from ductile to brittle. The different failure modes in the samples were revealed. The coal powder content is a key in the gas adsorption/desorption properties and an empirical formula for estimating the adsorption capacity was established. Based on the range analysis of experimental results, a multiple linear regression model of the mechanical parameters and their key influencing factors was obtained. Finally, a composition closely resembling the natural coal was determined, which differs by only 0.47–7.41% in all parameters except porosity (11.76%). Possible improvements and extension to similar materials are discussed. The findings of this study can help for better understanding of coal and gas outburst mechanism and stability of CO2 sequestration in soft coal seams.

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Quantitative evaluation of stress-relief and permeability-increasing effects of overlying coal seams for coal mine methane drainage in Wulan coal mine

Cited by 46 publications

References 32 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

Experimental study on evolution in the characteristics of permeability, deformation, and energy of coal containing gas under triaxial cyclic loading‐unloading

Experimental Development of Coal-Like Material with Solid-Gas Coupling for Quantitative Simulation Tests of Coal and Gas Outburst Occurred in Soft Coal Seams

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