| The prevention of coal and gas outburst is a major problem in the production of coal mine all around the world. In the former research of theinteraction mechanisms of coal and gas, it often ignored that the adsorption/desorption transforms the coal in the research on the deformation and dynamic development of the coal under different occurrence of gas in coal. In this paper, the coal containing gas is taken as the research object,on the base ofthe analysis in micro fine structure and study of gas occurrence, through the methods of laboratory simulation test and theoretical analysis, the deformation of coal under the effects of adsorption/desorption and control factors are in the research work. According to this thesis, asystemictest method of adsorption/desorption-induced deformationcan is obtained. The conclusions also reveal the rules of adsorption/desorption-induced deformation of coal in gas. It lays the theoretical foundationfor further comprehensive study of coal gas occurrence, the mechanism and technical approaches of preventing coal and gas outburst. In this paper, the main research results are as follows:①According to the former researches, pore characteristics and microstructure of coal in different rank wasstudiedtogether by laboratory tests. The results show that the differences of pore structure and morphology of different rank coals are obviously. Tectonism make pores at all levels of soft coal developed obviously compared to hard coal, including the greater pore volume and specific surface area, and better connectivity; tectonism also makes the difference of element enrichment between soft coal and hard coal: there are more metal oxide in the ash of soft coal; soft coal and hard coal have the same kind but defferent content functional groups, for the soft coal containing more weakly polar oxygen-containing functional groups, is conducive to the adsorption of methane in coal.② The Gas Adsorption/Desorption-induced Deformation Dynamic Testing Equipment was developed. This device has the advantages of simple structure, low processing cost, high reliability, flexible operation. It can realize synchronous test of strain and the adsorption capacity of different water content of coal specimensin different temperature and different gas pressures.The adsorption quantity of powder coal specimens can also be separatelytested in the above condition. According to the characteristics of the equipment, the methods of synchronistical testing coal adsorption/desorption strain and adsorption amount, andeffective porosity of coal were established. By using these methods, the isothermal adsorption/desorption amount inpulverized coal was preliminarily carried out, the results show that the isothermal process of adsorption/desorption of coal is reversible, but the desorbing process lags behind the process of adsorption.The isotherm of adsorption/desorption obeys Langmuir equation. In order to make the desorbingtest results more reliability, the state of completely desorbing(the adsorption desorption equilibrium pressure is 0MPa and the amount of residual adsorption is 0m L/g) should be takenas the fitting data points, and the lowest desorption equilibrium pressure is less than 0.5MPa.③ Based on the completely adsorption/desorption process test of raw coals and briquettes under different gas pressures,the deformation characteristics of the two kinds of coals are studied. The results show that the strain curve of the completely adsorption-desorption process of raw coal can be divided into six stages while three stages for briquette. Both of the adsorption swelling and desorption shrinkage of raw coal show anisotropy,while nearly isotropy for briquette. The swelling stage due to pressure relief in the completely adsorption/desorption process could express the characteristics of coal and gas outburst very well. While,the results also show that the deformation of two kinds of specimens are similar in adsorbing expansion and desorbing contraction, therefore, using briquette specimens instead of raw coal to explore the general law of adsorption-desorption-induced deformation characteristics is feasible.④ By proceeding from the forming force, cyclic loading-unloading and gas pressure, the effects of different test influence factors on adsorption/desorption-induced strain of coal were analyzed. The result shows that forming force, cyclic loading-unloading and gas pressure have a significant effect on the deformation of coal during desorbing and adsorbing. Based on the test results, the characteristics of the coal adsorption/desorption-induced deformation, should adopt the 50 k N(pressure of about 100MPa) molding coal sample test; at the same time, should avoid gas pressure to form a cyclic loading-unloading; in addition, for there is no relevant specification or technique requires about the method to take isothermal adsorption-induced deformation test, considering the GB/T 19560-2008, the distribution of coal gas pressure in China and the device performance, the maximum test pressure should not be less than 8MPa, but also can not be higher than 9MPa in high pressure isothermal adsorption/desorption-induced deformation test.⑤ The experimental study was carried out on single component gas adsorption/desorption of He, CH4 and CO2 and the deformation of different ranks of coal.Strain model of coal with different ranks in theadsorbing gas(CH4 and CO2) are analyzed. Based on the test results, the relationship between adsorption/desorption amount and strain of different ranks of coal were explored, and the model of the relationship between adsorption quantity and strain under CH4 atmosphere was established. Basing on the deforming mechanism in adsorption/desorption of coal, the coal isothermal adsorption/desorption-induced deformation model was established. The meaning of the parameters in the model is explicitly, it can describe the deformation mechanism of coal and the calculation results are also reliability. The model has been verified by tests.⑥ The desorption/adsorption amount and strain synchronous test of soft coal was carried out under different water content and temperature conditions. The influence of moisture and temperature on isothermal adsorption/desorption and deformation of soft coal was obtained. Based on this, the adsorption/desorption-induced deformation which respectively considered moisture and temperature was modeled.⑦ Basing on the adsorbing and desorbing deformation of coal under various influencing factors, the control of adsorbing and desorbing deformation to coal and gas outburst was studied. It indicates that there is a strong correlation between the deformability and the outburst risk of coal. The greater the expansion capacity is, the more beneficial of coal and gas outburst are. Soft coal is greater than hard coal in the outburst danger for it has much more elastic potentian energy and gas energy; because of carbon dioxide adsorption capacity is far greater than the adsorption capacity of methane, crushing energy of coal is lower, and the intrinsic gas energy is much more, resulting in the coal and Gas Outburst under carbon dioxide is greater than that under methane; for the same coal seam, the higher water content of coal, the lower the elastic potential energy and the intrinsic gas energy is more lower, and the outburst risk is more lower; When the increase of temperature is not big, the decrease of elastic potential energy will be not apparent. Conversely, the boost of temperature improves desorption. When the coal seam is broken under the ground stress, there will be more internal energy participate in the broken and ejection of coal, and which increases the risk of coal and gas outburst. |
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