承压破碎煤体渗透特性参数演化实验研究

为研究承压破碎煤体渗透特性参数演化规律,利用自主设计的承压破碎遗煤渗透率演化实验装置,开展了不同粒径配比煤样在不同轴压下的渗透率演化实验。实验结果表明:(1)在相同应力作用下,随着煤样粒径的增大,其渗透率逐渐变小,且较大粒径范围煤样的渗透率较小;在应力增加量相同的条件下,随着煤样粒径的增大,其渗透率的变化率越大,且混合粒径范围较大煤样渗透率的变化率均高于单一粒径或粒径范围小的煤样的变化率。(2)在较低孔隙压力范围内,煤样的渗透率均随孔隙压力的增大呈现出降低趋势,且存在一个轴压的临界值(9 MPa左右)。当轴压小于该临界值时,随着孔隙压力的增加,煤样渗透率的变化趋势更明显;而当轴压大于该临界值时,煤样渗透率的变化趋势较为平缓。(3)加载初期,随着孔隙率的减小,渗透率近似线性下降;当轴压达到9~12 MPa时,渗透率随孔隙率的下降较为平缓;继续增加轴压,渗透率随孔隙率的减小而急剧降低。

Experimental study on permeability parameter evolution of pressure bear broken coal

To study the evolution law of permeability parameter of pressure bear broken coal，the permeability evolution experiments of coal samples with different particle sizes under different axial pressures were carried out using the self designed experimental device for the coal permeability evolution.The experiment results show:① Under the same pressure，with the increase of coal sample particle，the permeability became smaller gradually，and the permeability of large range of coal sample particle was small.Under the same pressure increment，with the increase of coal sample particle，the permeability change rate became bigger gradually，and the permeability change rates of big mixed particle were higher than the change rates of single particle or small mixed particle.② In the lower pore pressure range，the permeability of coal samples showed a decreasing trend with the increase of pore pressure，and there existed a critical value of axial pressure (about 9 MPa).When the axial pressure was less than the critical value，with the increase of pore pressure，the permeability changing trend of coal sample was more obvious；and when the axial pressure was greater than the critical value，the permeability changing trend was more gentle.③ At the beginning of loading，with the decrease of the porosity，permeability declined approximately linearly；when the axial pressure was to 9-12 MPa，and the permeability decreasing trend was gentle relatively；continuing to increase the axial pressure，the permeability decreased sharply.