Abstract: In this paper, based on gas adsorption by the single coal body, both the hard and soft coal samples were chosed in the same air-intaking entry of one mine in Shanxi, and the samples were mixed hierarchically according to different quality ratio. In addition, the influence of mixed samples on gas adsorption characteristics under different quality ratios of hard and soft coal bodies were studied in the laboratory, by using Langmuir single molecule layer absorption theory. Then, the curves of adsorption quantity variation, the variation equation of adsorption constants a, b, and the initial speed of methane emission ΔP , with different mass ratios of hard and soft coal bodies, were obtained. Moreover, the effect of mass ratios of hard and soft coal bodies on gas emission were further analyzed. The results show that the adsorption constants a and initial speed of methane emission ΔP reach the maximum values, and the constants b reach the minimum value when the quality of soft coal is approximately equal to that of the upper hard coal. It implies that the gas adsorption quality and pressure of coal body all achieve the maximum values in this condition, and once the coal seam has been disturbed, large pressure gradient and concentration gradient will be formed, and large amount of methane gas will blow out. The research results provide theoretical foundation for the mechanism of coal and gas outburst.

Key words: mass ratio of hard and soft coal, adsorption characteristic, adsorption constant, initial speed of methane emission