地质雷达探测顶板离层的数值与物理模拟研究

Numerical and physical simulation of the detection of roof separation with ground penetrating radar

根据顶板离层的结构特点构建了三层介质模型,通过模拟观察电磁波的传播衰减特征与覆岩介质介电常数的关系,研究相对介电常数的差异对地质雷达探测效果的影响。基于时域有限差分法,运用GPRmax软件对二维电磁波在不同介质的自由空间中的传播进行正演模拟。对4种不同性质的覆岩进行离层探测,得出当顶板离层与围岩的相对介电常数差异越大时其探测的效果更佳。使用Seeker SPR 500EX地质雷达系统进行物理模拟实验,运用Reflex W2D数据分析软件对实验结果进行分析,得到良好的探测结果。

A three-layer medium model was constructed according to the structure characteristics of roof separation. The relationship between the propagation attenuation characteristics of electromagnetic wave and the relative permittivity constant of overlying strata was observed through simulation, and the influences of relative permittivity constant difference on the detection effect by ground penetrating ra- dar（GPR） was thus studied. Then, the propagation of the 2D electromagnetic wave in the free space of different media was made through forward modeling with GPRmax software based on the time-domain finite-difference method. After separation detection on four kinds of overlying strata with different properties, it was obtained that the detection effect was more optimal as there was a bigger difference in the relative permittivity constant between the roof separation and surrounding rocks. Finally, a physical situation experiment was carried out with GPR system of the Seeker SPR 500EX, the experimental re- sult obtained was further analyzed with data analysis software of ReflexW2D, and favorable detection target was achieved.