煤单轴压缩介电常数与电磁辐射同步响应实验研究

Experimental study on the synchronous response of dielectric constant and electromagnetic radiation under uniaxial compression of coal

为了研究单轴加载条件下,煤在不同变形和破坏阶段的相对介电常数与电磁辐射的响应规律,建立了针对单轴压缩煤的裂纹、电性参数和电磁辐射的同步监测系统,分别测试了不同煤种在垂直层理方向上单轴载荷过程中相对介电常数和电磁辐射脉冲数随时间的变化特征,研究其变化规律。研究结果表明:微裂隙压密阶段,随着煤孔隙和裂隙的闭合,电磁辐射脉冲数增加,相对介电常数有一定程度的波动;弹性变形阶段,电磁辐射脉冲数和相对介电常数变化减小,相对介电常数变化曲线接近线性;在裂隙发生和扩展阶段,与前一阶段相比,电磁辐射脉冲数有所增加,相对介电常数有一定的波动,呈现先减小后增大的趋势;在裂隙不稳定发展直至破裂阶段,电磁辐射脉冲数出现峰值,相对介电常数变化波动明显,在应力峰值之前呈现先增大后减小再增大的趋势。通过对相对介电常数和电磁辐射脉冲数的同步对比分析得出,电磁辐射脉冲数增长一般出现在相对介电常数变化较大的区域。

In order to study the response of relative dielectric constant and electromagnetic radiation of coal at different stages of deformation and failure under uniaxial loading conditions,a synchronous monitoring system for cracks,electrical parameters and the pulse number of electromagnetic radiation of uniaxial compression coal was established.The variation characteristics of relative dielectric constant and electromagnetic radiation with time were tested respectively in the vertical bedding direction of different coal under uniaxial loading,and the variation regularity was discussed.The research results indicate that during the compaction stage of micro-crack,the pulse number of electromagnetic radiation increases and the relative dielectric constant fluctuates to a certain extent with the closure of coal pores and fissures.During the elastic deformation stage,the pulse number of electromagnetic radiation and change of relative dielectric constant decrease and the change curve of relative dielectric constant is close to be linear.During the occurrence and propagation stage of crack,the pulse number of electromagnetic radiation increases compared to the previous stage,the relative dielectric constant fluctuates to a certain extent,and shows the trend of first decreasing and then increasing.During the stage of unstable development of crack until the stage of fracture,the pulse number of electromagnetic radiation shows the peak value,the relative dielectric constant fluctuates obviously and tends to increase at first,then decrease and finally increase again before the stress peak.Through the comparative analysis of relative dielectric constant and the pulse number of electromagnetic radiation,it is found that the increase of electromagnetic radiation generally appears in the area with the large changes of relative dielectric constant.