Optimization study of surface comprehensive geophysical detection methods of coal mine goafs

In order to realize fine comprehensive geophysical detection for coal mine goafs,based on the analysis of type classification,characteristic and applicabl e conditions of the mature surface geophysical methods,comprehensive geophysical cases ,the optimization of surface comprehensive geophysical methods was carried out.The results showed that in order to achieve accurate comprehensive surface detection,two or more comprehensive geophysical detection methods should be adopte d.Among them,the very shallow goafs with depth less than 50 m were fit for ground penetrating rada method and multi-electrodes resistivity method;the shallow goafs w ith depth between 50 m and 150 m were fit for 2D seismic method,Time domain electromagnetic method or Multi-electrodes resistivity method;the medium-depth goafs with depth between 150 m and 400 m were fit for 2D or 3D seismic method,time domain electromagnetic method,controlled-source audio magnetotellurics method or au dio magnetotellurics method;the deep goafs with depth more than 400 m are fit for 3D seismic method,controlled-source audio magnetotellurics method, audio magnetot ellurics method or time domain electromagnetic method.