破碎煤体渗透特性的试验研究

Experimental study of permeability of broken coal

破碎煤体的渗透特性是影响煤矿瓦斯抽放和地下采空区突水灾害预防的重要因素之一。利用一种专用的破碎岩体压实渗透试验装置,在MTS815.02岩石力学伺服试验系统上完成了破碎煤体压实过程中的渗透特性测定,得到了破碎煤体轴向应力、渗透压差、水头梯度与渗流速度的关系,并分析了各种粒径破碎煤体在不同渗透速度下轴向应力对渗透系数的影响。研究表明,(1)不同粒径破碎煤体的渗透特性与其压实状态密切相关,轴压从5～15MPa变化时,渗透压差的最大值增加了3.28～166.47倍,渗透系数都相应降低了1个量级以上;(2)在恒定的渗流速度下渗透压差随轴压变化的规律近似呈指数函数关系;(3)渗透系数随轴压变化的规律近似呈对数函数关系;(4)恒定的轴压下水头梯度随渗流速度变化的规律近似呈指数函数关系。

Much attention should be paid to the permeability of broken rocks in goaf for the sake of the gas outburst and disaster prevention. Using a special device together with the MTS815.02 Rock Mechanics Test System, we tested the permeability of broken coal during its compacting process, getting the relations between the axial stress and the differential seepage pressure and between the pressure gradient and the seepage velocity. The effects of axial stress, grain size, and seepage velocities on the permeability coefficient are analyzed. The results show that the permeability of broken coal with different sizes is closely related with its compaction state： （1） the maximum value of seepage pressure will increase 3.28-166.47 times as the axial stress changing from 5 MPa to 15 MPa; the permeability coefficient of broken coal will decrease one magnitude; and （2） for a constant seepage velocity, the differential seepage pressure and the axial stress can be expressed by an exponential function; and （3） for a constant axial stress, the pressure gradient and the seepage velocity can be also expressed by an exponential function; and （4） the permeability coefficient of broken coal will decrease with the increase of axial stress, having a logarithm functional relation between them.