粗糙表面对煤岩界面探地雷达识别结果影响研究

doi:10.11799/ce202411026

摘要/Abstract

摘要： 在低照度、高浓度粉尘的综采工作面，探地雷达是解决煤岩界面识别难题的有效方法。针对现有研究忽略粗糙煤岩界面对识别结果影响的问题，采用蒙特卡罗方法生成具有不同均方根高度和相关长度的粗糙表面，并叠加至岩层走向起伏的煤岩界面，利用时域有限差分方法进行煤岩地质模型的正演模拟实验，以研究煤岩界面粗糙度对界面位置及后向散射波振幅的影响规律。实验结果表明，当粗糙煤岩界面的均方根高度大于1/4波长单位时，多径效应引起的电磁波干涉现象导致煤岩界面识别结果较差，当其均方根高度大于1个波长单位时，识别基本失败|粗糙煤岩界面的相关长度对识别结果影响较小，界面位置及后向散射波振幅变化与界面走向起伏规律近似一致。粗糙空气-煤壁界面均方根高度增加时，其回波会与煤岩界面后向散射波在局部位置发生电磁波干涉效应，导致煤岩界面识别困难。

关键词: 煤岩界面, 粗糙表面, 探地雷达, 均方根高度, 相关长度

Abstract: In low-light and high-dust concentration environments of fully mechanized mining faces, ground-penetrating radar (GPR) is an effective method for addressing the challenge of coal-rock interface identification. To address the issue of existing research neglecting the impact of rough coal-rock interfaces on identification results, this study employs the Monte Carlo method to generate rough surfaces with varying root mean square (RMS) heights and correlation lengths. These surfaces are superimposed onto a coal-rock interface with undulating geological features. Using the finite-difference time-domain (FDTD) method, forward modeling experiments are conducted to investigate the impact of coal-rock interface roughness on the position of the interface and the amplitude of backscattered waves. The experimental results indicate that when the RMS height of the rough coal-rock interface exceeds 1/4 of the wavelength, multipath effects cause electromagnetic wave interference, leading to poor identification results. When the RMS height exceeds one wavelength, the identification essentially fails. The correlation length of the rough coal-rock interface has a smaller impact on identification results, with the variations in interface position and backscattered wave amplitude closely following the interface undulations. In practical applications of GPR for coal-rock interface identification, it is crucial to account for the impact of rough interfaces on identification results and to perform corresponding time delay and amplitude compensation. Increasing the root mean square height of the rough air-coal wall interface causes its echo to interfere with the coal-rock interface echo at local positions, making the identification of the coal-rock interface difficult.

施从伟, 高忠斌. 粗糙表面对煤岩界面探地雷达识别结果影响研究[J]. 煤炭工程, 2024, 56(11): 176-181.

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