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利用自主研发的含瓦斯煤热流固耦合三轴伺服渗流装置,以无烟煤型煤试件为研究对象,进行不同轴压、围压条件下气体压力加卸载过程中渗流试验研究,模拟不同煤层深度,以探讨煤变形及瓦斯运移演化规律。研究结果表明:(1)在加载过程中,煤应变量减小,吸附瓦斯产生较大的膨胀变形,呈现线性关系,在卸载过程中,煤应变呈增大趋势,煤逐渐被压缩。随轴压、围压增大,下降单位气体压力引起的煤应变升高量降低,应变响应程度减小。(2)在加载过程中,随气体压力升高,渗透率先减小后增大趋势,煤渗透率呈类似“V”型变化趋势,气体压力在1.2 MPa左右存在明显的拐点,体现煤孔隙扩张的程度和吸附瓦斯层增厚程度影响,依赖于吸附作用或有效应力占主导地位。在卸载过程中,随着气体压力降低,煤渗透率呈先减小后增大趋势,渗透率增大且变化速度加快,主要依赖有效应力作用或基质收缩的主导地位差异。(3)随有效应力的增大,煤渗透率呈先减小后增大的趋势。煤渗透率随有效应力增大呈对数函数或指数函数关系。(4)气体压力具有典型二阶段特征,同时渗透率与体积应变具有密切关系,体现出有效应力、吸附膨胀与煤基质收缩同时对裂隙等内部结构的影响。
Using self-developed coal-gas thermal-solid coupling three-axis servo oil seepage device, taking the anthracite-type coal sample as the research object, the seepage test during gas pressure loading and unloading under different axial compression and confining pressure was conducted to simulate the coal seam depth , In order to explore the evolution of coal deformation and gas evolution. The results show that: (1) During the loading process, the amount of coal strain decreases and the gas appearing in the gas expands greatly, showing a linear relationship. During unloading, the strain of coal increases and the coal is gradually compressed. With the axial compression, confining pressure increases, the descending unit of gas pressure caused by coal strain increases decreased, the degree of strain response decreases. (2) During the loading process, with the increase of gas pressure, the permeability decreases first and then increases. The permeability of coal shows a similar trend of “V ”. There is a significant inflection point at about 1.2 MPa of gas pressure, The degree of pore expansion and the degree of thickening of the adsorbed gas layer depend on the adsorption or effective stress dominance. During the process of unloading, with the decrease of gas pressure, coal permeability decreases first and then increases, permeability increases and the rate of change accelerates, mainly depending on the dominant position difference of effective stress or substrate shrinkage. (3) With the increase of effective stress, the permeability of coal decreases first and then increases. Coal permeability increases with the effective stress logarithm function or exponential function. (4) The gas pressure has typical two-stage characteristics. At the same time, the permeability is closely related to the volumetric strain, which shows the effect of effective stress, adsorption and expansion and coal matrix shrinkage on the internal structure of the fracture.