不同应力和瓦斯压力下煤的相对介电常数变化规律

Law of relative dielectric constant of coal under different stresses and gas pressures

为了研究含瓦斯煤样相对介电常数变化规律,利用自制的含瓦斯煤岩电性参数测试系统,对不同应力和瓦斯压力下含瓦斯煤样的相对介电常数进行了研究,并探究了应力、瓦斯影响煤体相对介电常数的机理。结果表明:在同一频率下含瓦斯煤样的相对介电常数随轴压、瓦斯压力的增加而增加,应力增加时,煤内部孔隙被压缩,煤分子电子云之间的重叠空间增大,电子云中的电子容易发生迁移,极化率增加,相对介电常数随之增大;煤对瓦斯的吸附能力越强,煤吸附的瓦斯越多,煤样的孔裂隙结构受影响程度越大,吸附释放的热也就越多,煤膨胀效应越明显,最终表现为煤样的相对介电常数所受的影响就会越大;煤样相对介电常数发生变化的机理主要是煤体内电子极化、离子极化、转向极化和界面极化综合作用的结果。

In order to study the law of the relative dielectric constant of coal containing gas,the relative dielectric constant of coal containing gas under different stress and gas pressure is studied by using selfmade electrical parameter test system,and the effect of stress and gas pressure on the relative dielectric constant of coal containing gas is analyzed. The research results show that the relative dielectric constant of coal containing gas increases with the increase of the axial pressure and gas pressure under the same frequency. The pore size in coal was compressed with increasing stress and the overlap space increases between the electron cloud of coal molecular,which make the electron cloud transfered easily and make the polarizability and the relative dielectric constant increase. The higher coal adsorbing gas capacity,the more gas adsorption amount in coal under the same gas pressure,which make the coal pore structure be affected significantly,the adsorption heat and the coal expansion deformation much higher. Finally,the relative dielectric constant could be affected significantly. The mechanism of the changes of relative dielectric is mainly compressive effect of electronic polarization,ionic polarization,steering polarization and interface polarization in coal.