Coal Mine Goaf Interpretation: Survey, Passive Electromagnetic Methods and Case Study

Coal mine goaf detection remains confronted with the lack of fast, effective and low-cost exploration means, especially for accurate prediction mining threats primarily caused by hydraulic infiltration. The rapid popularization passive electromagnetic methods has contributed greatly to improving interpretation effects different types goafs. This paper, firstly, summarizes pros cons various in detection. Then, feasibility using novel (e.g., super low frequency alternating magnetic component method (SLF) audio magnetotelluric (AMT)) is proposed further discussed. With well-designed geo-electrical models, theoretical results demonstrate that semi-quantitative SLF responses can be directly used delineation target layer estimated depth range. In contrast, 3D inversion provides more information about conductive targets appropriate initial model selection. shallow, low-resistive accurately allocated maps. Moreover, real data from study areas utilize effectively identify fault structures, indirectly contributes judge collapse locations favor describing potential distribution fracture water Combined three-dimensional (3D) resistivity AMT data, water-rich within 400 m were revealed. inverted distributions are basically consistent those water-filled goafs surrounding layers, which also confirmed known logging data. detailed delineations water-control zones inferred relate aquifers some areas; this reveal collapses require successive planning. specific working faces, risks have been handled advance strengthening continuous monitoring level inflow. above verification laid a practical foundation predicting collapse-type or coal