煤火区浅部松散煤体及采空区的探地雷达响应特征

GPR RESPONSE CHARACTERISTICS OF SHALLOW LOOSE COAL SEAM AND GOAF IN THE COALFIELD COMBUSTION AREA

探地雷达对浅层勘探具有较高分辨率,为煤田火区浅部松散煤体或采空区等典型火源地质结构探测提供了重要手段。然而如何识别各种火源地质结构体,确定火区重点范围还存在一定的理论不足。基于电磁波理论,采用时域有限差分法正演模拟了火区典型地质体地电模型雷达响应,其特征表现为:松散跨塌煤体对应雷达响应绕射波严重,其内部波形紊乱;空洞区顶界面回波能量强,较为连续,其内部无绕射。正演模拟和现场测试研究表明:探地雷达对识别浅埋火区煤层松散跨落程度,圈定火烧重点区域,减少灭火成本和火区开采安全事故具有重要的现实意义。

With high resolution for shallow exploration, Ground Penetrating Radar （GPR） provides an significant means for exploring typical geological struelures like loose coal seam and goal in the coalfield combustion area. However, it is difficult for GPR to distin- guish wlrious kinds of burning geological structures and delineate the key combustion area because of shortage of theories. Based on e- lectromagnetic wave theory, the authors conducted florward simulation of the geoelectric models of typieal burned coal in the eoalfieldcombustion area by using Finite Difference Time Domain （FDTD）. The radar response characteristics of numerical computation indi- cate that serious diffracted waves appear from the part of loose collapse coal seam, and reflected waves from the top of the cavity have high energy and are continuous. Forward simulation and field test demonstrate that, with GPR, we can distinguish the loose degree of the burning coal seam and delineate the key combustion area so as to reduce the cost of fire-fighting. This is of great significance for safe combustion mining.