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为了研究割缝预抽后煤瓦斯吸附特性的变化特征,以杨柳煤矿10煤层7个煤样为研究对象,采用甲烷等温吸附实验测定煤样的Langmuir方程吸附常数a和b,通过压汞实验和低温液氮吸附实验的有机结合,表征煤样孔径分布和比表面积的变化。结果表明:(1)随着煤样与割缝孔距离的增大,吸附常数a呈逐渐增大的趋势,而吸附常数b的变化趋势则相反,但与甲烷等温吸附曲线的曲率变化趋势一致。(2)随着煤样与割缝孔距离的增大,煤样孔径分布发生显著的变化,吸附孔孔容比从33.27%增大到55.38%,比表面积从7.254 m2/g增大到9.856 m2/g。(3)割缝预抽后,煤样参数曲线(Langmuir方程吸附常数、吸附孔孔容比和比表面积)的变化幅度均呈现出平缓→急剧→平缓的趋势,具有有界性和非线性的特征,符合Boltzmann方程。割缝预抽后煤瓦斯吸附特性的变化存在明显的分区特征:变化显著区(小于1.8 m)、变化过渡区(1.8~4.5 m)和变化不显著区(大于4.5 m)。(4)割缝预抽后煤体瓦斯压力下降,有效应力增大,进而控制煤体的吸附特性。研究结果可以为煤层水力割缝增透实践提供可靠的基础理论支撑。
In order to study the characteristics of coal gas adsorption after cutting pre-pumping, seven coal samples of No.10 coal seam in Yangliu Coal Mine were studied. The adsorption constants a and b of Langmuir equation of coal sample were determined by methane isothermal adsorption experiment. The organic combination of low temperature liquid nitrogen adsorption experiments characterizes the pore size distribution and specific surface area of coal samples. The results show that: (1) As the distance between the coal sample and the kerf hole increase, the adsorption constant a increases gradually, while the adsorption constant b changes in the opposite direction. However, the change tendency of the adsorption constant is the same with the methane adsorption isotherm curve . (2) With the increase of the distance between the coal sample and the kerf hole, the pore size distribution of coal samples changed significantly. The pore volume ratio of adsorption pores increased from 33.27% to 55.38%, and the specific surface area increased from 7.254 m2 / g to 9.856 m2 / g. (3) After the pre-pumping of kerf, the change range of the parameter curve of coal sample (Langmuir equation adsorption constant, pore volume ratio and specific surface area of adsorption pores) showed a trend of gentle → sharp → gentle, with bounded and non-linear Characteristics, in line with the Boltzmann equation. There are obvious zoning characteristics of coal gas adsorption characteristics after cutting pre-pumping: significant change (less than 1.8 m), transitional zone (1.8-4.5 m) and insignificant change (more than 4.5 m). (4) After pre-pumping slotted coal gas pressure decreased, the effective stress increases, and then control the adsorption characteristics of coal. The results of this study can provide reliable basic theoretical support for hydraulic cutting seam penetration enhancement.