Transient electromagnetic response of double magnetic source in coal seam roof disaster caused by water and its application

The concealed water body in the coal seam roof is one of mine water disasters and the mine transient electro-magnetic method is one of main methods to detect the source of mine disaster water. However,it cannot meet the re-quirement from the coal mine with great depth due to its small transmitting magnetic moment. Based on above consid-eration,a new method is proposed to use double magnetic sources,one located in the coal mine roadway and the other one located at the surface,to detect coal seam roof from two directions. Besides,the numerical simulation method is used to simulate the different geo-electrical model by using finite difference method and comparison between the result of magnetic source transmitting on the ground surface and receiving information in the roadway and the result of double magnetic sources located on the ground surface and in the coal mine roadway and the receivers located in the roadway. As a result,the modeling results show that there are existing great difference of electromagnetic responses for two dif-ferent geo-electrical models,one with good water abundance and the other one with poor water abundance. The ampli-tude of induced potential decay curve of geo-electrical model with good water abundance is smaller than that with poor water abundance on the left of cross point,inversely,the amplitude of induced potential decay curve of geo-electrical model with good water abundance is relatively larger than that with poor water abundance on the right of cross point. Hence,these characters of the curve are related with the water abundance of the coal seam roof. Besides,The authors measure the data of different typical mine hydrogeological structures and the detecting results show that the characters of curves are similar with numerical simulation. Therefore,this study provides a new method for the detection of con-cealed and damaging water bodies in the coal seam roof for great depth coal mine and it has certain theoretical signifi-cance and practical value.