Application of time domain electrical source ground airborne electromagnetic system in goaf water exploration

In order to realize the fast and accurate exploration of coal mined-out area and goaf water in southeastern Qinshui Basin under complex terrain conditions in mountainous area,a geophysical exploration using time-domain elec-trical source ground airborne electromagnetic method was conducted in the area above. Time-domain ground airborne electromagnetic method adopts the method of ground launching while air receiving. The long wire source is laid on the ground. High power transmitter is used to transmit time-domain square wave signal to the underground while UAV is used to carry the receiving system along the predetermined route parallel to the launching source for the flight detection and acquisition of electromagnetic signal and coordinate information of measuring points. The electromagnetic data transmitted and received are synchronized by GPS clock. In this paper,the electromagnetic data with high signal-to-noise ratio are collected by using the time-domain electrical source ground airborne electromagnetic detection system. At the same time, the baseline correction method of ground airborne electromagnetic, the suppression method of ground-to-air electromagnetic noise and the apparent resistivity imaging method are used to further improve the quality of electromagnetic data and imaging resolution. The apparent resistivity of ground airborne electromagnetic is obtained by processing the time-domain electrical source electromagnetic data and spatial coordinate information,and the spatial distribution characteristics of mined-out area and goaf water area are deduced and explained by combining the known geological information. The time-domain electrical source ground airborne electromagnetic method not only greatly re-duces the workload on the ground,but also takes into account the exploration depth. Therefore,it has the characteris-tics of fast and efficient airborne electromagnetic method and large exploration depth of surface electromagnetic meth-od. The exploration shows that the system can improve the efficiency by 4-5 times,and the exploration effect is basi-cally consistent with the known geological information. It shows that the time-domain electrical source ground airborne electromagnetic detection system can realize the rapid and accurate exploration of coal mined-out areas. In view of the effect of this exploration,it can be expected that the time-domain electrical source ground airborne elec-tromagnetic detection system will play an important role in deep resources exploration,environment,engineering and disaster geo-logical survey under the complex terrain conditions.