利用煤体破裂电磁信号进行局部震源定位方法研究

准确预测煤岩破裂震源方位,确定采掘工作面重点灾害区域,可以使煤岩动力灾害防治措施更为有效.根据煤岩变形破裂电磁效应规律和电磁波基础理论,提出了一种利用电磁信号能量来确定局部震源方位的方法,并通过实验室定向接收实验和平煤十矿现场测试验证该方法的有效性.结果表明,电磁信号强度随着煤岩体应力状态变化而变化;两个正交天线接收的电磁信号能量分别与各自接收夹角余弦值的平方成正比,利用此比例关系可以确定震源的方位;电磁信号定位方法与静态指标法预测局部区域危险性具有较好的检验一致性.研究成果为煤岩动力灾害重点灾害区域的判定提供依据.     

煤矿采掘过程中煤岩体电磁辐射特征及应用

运用研制的KBD5矿用本安型电磁辐射监测仪测试了煤矿采掘过程中工作面煤岩体的电磁辐射，分析了电磁信号与采掘工艺及煤岩动力灾害危险性等的关系。研究表明，煤矿采掘过程伴随产生电磁辐射，电磁辐射是煤岩体受到采动影响后应力重新分布或变形破裂趋向新平衡的结果；有煤与瓦斯突出和冲击地压危险时，有明显的电磁异常前兆；采取防治措施后，电磁辐射显著下降。电磁辐射技术在煤矿可以用于预测煤与瓦斯突出、冲击地压等煤岩动力灾害。     

岩石破裂电磁辐射频率与弹性参数的关系

为进一步研究岩石破裂电磁辐射特征,本文根据岩石破裂电磁辐射是由岩石破裂时产生带电粒子扰动引起的假说,通过断裂力学理论中的张开位移法计算岩石破裂过程中的裂纹宽度,由电磁辐射频率与破裂宽度之间的关系,研究电磁辐射频率与弹性参数之间的关系,并给出了它们之间的关系表达式.通过建立具有中心贯穿裂纹的无限大平板模型,根据破裂宽度计算了在该模型条件下几种岩石破裂过程中产生电磁辐射频率范围.理论模型计算出来的频率范围主要集中在实验观测的中高频段,并体现出频率随弹性参数的变化.     

Determination of directions of horizontal principal stress and identification of active faults in Kachchh (India) by electromagnetic radiation (EMR)

The Kachchh basin in the western India is known for its recent high seismicity. This study presents an application of the geogenic Electromagnetic Radiation (EMR) technique for deciphering the directions of principal horizontal stress in the eastern Kachchh. The principal direction of horizontal stress obtained from EMR differs from those obtained from earthquake focal plane solutions. The major horizontal principal stress based on the EMR study shows an azimuth of N60°E ± 10°. The principal directions of EMR emissions are parallel to the acute bisector of conjugate microcracks. The azimuthal distribution of EMR signal and dimension of microcracks suggest that the EM emissions are transversely polarized.The study also deals with the first application of electromagnetic radiation emissions to identify active fracture planes in sandstones that could become potential active faults later, which might be seismogenic or nonseimogenic. This study is based on linear profiling at six different places across two major faults, the Kachchh Mainland Fault (KMF) and the South Wagad Fault (SWF) in the eastern Kachchh. Anomalously, high EMR emissions are observed in the eastern part of the KMF, indicating active surface deformation.     

三维地形频率域人工源电磁场的边界元模拟方法

提出了一种用边界元法计算频率域人工源三维地形电磁场的数值模拟方法.首先用矢量积分理论和电磁场边界条件,将上半空间（空气）和下半空间（地下介质）两个区域电磁场边值问题变为仅对地形界面的两个矢量面积分方程.然后将对地形界面的积分剖分为一系列的三角单元积分.在三角单元积分中,假设单元中电磁场为无限大气空间电磁场与地形影响的叠加,并假设地形影响为常项,这样既保证了计算精度又使得计算方法简便.通过分解和计算,每一个矢量面积分方程分解为对应三个坐标方向的三个常量线性方程,这些线性方程组成了对角占优的线性方程组,可用SSOR方法求解.文中给出了垂直磁偶源的垂直磁场地形影响的例子.