| Coal seam gas drainage technology can not only effectively prevent coal mine gas disasters,but also realize the utilization of coalbed methane.In this paper,through the combination of experimental testing,theoretical analysis and numerical simulation,the characteristics of pore cracks of different coals are analyzed,the gas diffusion dynamics of coal particles of various sizes are discussed,and a multi-physics coupling mathematical model of mining coal seam is constructed.Taking the gas drainage of 416 fully mechanized coal mining face in Yaxing Coal Mine of Inner Mongolia as the engineering background,the influence of various factors on the gas drainage effect was studied,and the coupling law of multi-field mining coal seam was clarified to provide a basis for solving practical engineering problems underground.The main results are as follows:(1)The coal samples at Yaxing Mine were mainly used as supplements to other mines.The tests of the physical and mechanical properties and the analysis of pore structure characteristics of coal rocks with different degrees of metamorphism were carried out.The comprehensive image analysis method and fluid injection method were used to describe the pore fissure characteristics of coal rocks.(2)A dynamic acquisition experimental platform for gas diffusion was set up to realize the precision and automation of the diffusion test.Using this platform,the desorption and diffusion characteristics of coal gas with different sizes are studied.The results show that: As the pore pressure gradually increases,the limiting diffusion rate of the coal body increases.There is a critical interval for the difference in the effective diffusion coefficient of coal samples.When the coal particle size does not rise to this interval,the diffusion coefficient decreases slowly with the increase of the particle size;when the particle size exceeds the critical interval,the diffusion coefficient gradually stabilizes at Near a fixed value..(3)The tortuosity of the pores of different coal bodies and the length of diffusion channels were calculated,and the order of the gas diffusion capacity of the four coal bodies was quantitatively analyzed.Gas diffusion models of coal particles with different particle size scales are given,and the multi-level stacking effect of coal particles with different particle size scales is studied.(4)According to the situation of the No.416 working face of the Yaxing coal mine in Inner Mongolia,a three-dimensional geometric model of the mining coal seam was established,and the stress distribution law of the coal body in front of the working face was clarified.A single-hole gas drainage model considering the coal body heterogeneity and anisotropy in the original rock area was established,and the rationality of the model was verified by the field drainage flow data.The influence law of different parameters on the effective area of gas drainage is revealed,which in turn guides and determines the scientific and efficient plan of the hole layout.(5)A multi-field coupling mathematical model of stress deformation,stress damage,gas diffusion and gas seepage in mining coal seams was constructed,and the temporal and spatial evolution of coal permeability and gas pressure in front of the working face were analyzed.The results show: As the distance from the working face increases,the permeability of the coal body shows a continuous and asymmetric "U" shape distribution law,and the gas pressure of the coal body shows a continuous and irregular "n" shape distribution law.During the master’s degree,6 papers were published.Among them,the first author or corresponding author published 1 SCI paper and 2 core Chinese papers.Applied for 6 national invention patents,including 2 authorized invention patents and 2 utility model patents.Independently presided over and completed the Jiangsu Province Graduate Practice Innovation Program(No.SJCX18-0667).There are 46 figures,9 tables and 113 references in this thesis. |
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