复杂断层构造电磁波衰减系数层析成像模拟研究

传统矿井电磁波透视层析成像技术只考虑电磁波的传播距离而忽视传播的方向性,造成探测复杂构造时的层析成像分辨率较低。依据电磁波在煤岩介质中的传播规律推导出了与入射角有关的新振幅衰减常数。引用新振幅衰减常数并基于代数重建算法建立了层析成像数学模型,编制了程序软件。利用新振幅衰减常数层析成像算法分别对平行和交叉断层进行数值模拟。通过与传统衰减常数层析成像的效果进行对比,结果表明:改进后的新振幅衰减常数层析成像效果更好,对断层的位置、走向、延展长度等情况反映清晰准确;在介质背景衰减场不易确定的情况下,绝对衰减层析成像方式优于相对衰减层析成像方式;平行关系的断层构造分辨率要高于交叉关系的断层构造。通过在某采煤工作面的电磁波层析成像中成功圈定了一组隐伏的平行断层构造实例,说明采用新衰减常数的层析成像技术效果提高明显。

The Simulation Research of Electromagnetic Wave Attenuation Coefficient Tomography in Media of Complicated Fault Structures

Traditional mine electromagnetic wave perspective tomography techniques only consider the propagation distance while ignoring the directionality of transmission which causes the resolution of tomographic imaging to be lower in the detection of complex structure. According to the propagation law of electromagnetic waves in coal medium, a new amplitude attenuation constant involving incidence angle is deduced in this paper. Base on the algebraic reconstruction algorithm, tomography mathematical model is built by introducing the new amplitude attenuation constant, and the software is compiled. The new method is used to do simulation for parallel faults models and cross faults models respectively. By comparison with the traditional method, the results show that the improved amplitude attenuation constant has better effect and it can accurately and clearly indicate position, trend and extension length of complicated fault structures. In addition, the results also show that absolute attenuation tomography method is much more superior to the relative attenuation tomography method in case of attenuation value of media background not being easy to be determined. The resolution of parallel faults is higher than that of cross faults. Finally, a successful example of locating a hidden parallel faults in a coal working face indicates that the effect is enhanced a lot by adopting the improved attenuation constant tomography technique.