Study On Vector-Intersecting Interpretation Method Of Surface-to-Underground Transient Electromagnetic Data

The surface-underground transient electromagnetic method is proposed as an innovative detection technology due to the shortcomings of the ground transient electromagnetic method and mine transient electromagnetic method.It has a good application prospect in the detection of water sources of hidden water inrush disasters in coal mines for this technology overcomes the shortcomings of the ground and mine transient electromagnetic methods and integrates their advantages.The observation methods of this technology transmission on ground and receiving in tunnel space,it cannot simply transplante the original method and technology in data processing and interpretation.We equate the transient magnetic fields at different times to a series of continuous static magnetic fields using the concept of "dynamic and static" transformation.In order to achieve directly and rapidly spatial positioning of electrically abnormal bodies,we proposed a surface-underground transient electromagnetic vector-intersecting interpretation method based on the theory of spatial distribution of static magnetic field.The main research contents are as follows:(1)According to the three-component expression of the step current electromagnetic field of the rectangular loop source in free space,the space-time distribution characteristics of the excitation magnetic field of the rectangular source are calculated.The results show that the composite vectors observed in each plane direct to the center of the transmission loop and have its own characteristics,which is provides a basis theoretical for the realization of vector intersection technology.(2)Expounded the theory and method of vector intersection technology and formed the surface-underground electromagnetic vector intersection interpretation technology based on the theory of "equivalent eddy current loop".(3)Established multiple sets of surface-underground transient electromagnetic detection geophysical models of surface-underground electromagnetic detection and obtained the transient magnetic signal response characteristics of different geoelectric models by numerical calculation.Discussed the positioning effect of vector intersection technology with different conditions(resistivity difference,the difference in the spatial position of the anomalous body,the choice of different time channels,the impact of low-resistance overlays,the presence of coal seams,layered horizontal stratum)through the vector intersection processing of the three electromagnetic components,and explored the applicability of this detection method.The results claim that the positioning effect is different under different conditions and there is a certain error in positioning in the z direction,but as a whole,the vector intersection technology is feasible to achieve the spatial positioning of different abnormal bodies.(4)Further analysis of the reasons for inaccurate positioning in the z direction of the surface-underground transient electromagnetic method vector intersection technology and put forward non-linear fitting on the correction factors at different line offsets to improve the positioning accuracy in the z direction.This paper includes 60 pictures,5 tables,and 88 references.