Research On The Application And Resolution Of TEM Exploration Of Coal Mine Goaf

In the context of today’s energy shortage, the coal production increased year byyear that led to the upper coal seam used up. Mining the deeper coal seam is the mainmeans to make up the gap of the sources of energy. After mining the coal seam, it willform goafs underground mining area. In recent years, gob collapse and flood accidentoccurred frequently that is the major hidden danger for people’s production and living.Transient electromagnetic method belongs to the electromagnetic method in timedomain, and it is favored by many geophysical prospecting workers because of simpledetection device, high construction efficiency and high sensitivity ability for lowresistance targets. So the transient electromagnetic method is widely used in the fieldof exploration, especially getting rapid development in the field of coal goafdetection.This paper focuses on the practical application. Firstly, the paper will introduce thegeneral situation of development of transient electromagnetic method; derive theformulas of the forward response; study the inversion method of Occam; implementone dimension forward modeling and inversion algorithm and test the accuracy withsynthetic data. Secondly, it analyses forward responses and attenuation curves forsome goaf models (single-layer, double-layer, ponding, no ponding). It is alsoconcluded that the anomalous responses of coal goaf are changing with attenuationcurve, not time characteristics. From the forward modeling results of coal seams,transient electromagnetic method has high detecting sensitivity in the ponding goafswith low resistivity, however, for the no ponding goafs with high resistivity, theanomalous responses are not obvious, unable to detect accurately. When detectingdouble coal seams goaf, if the upper is low resistivity area, the anomalous responsesof forward responses can be found clearly; if upper goaf is high resistivity area andlower goaf with low resistivity or high resistivity, forward responses for anomalousbodies cannot be found easily. Then, by analyzing and testing forward modelingresults and one dimensional Occam inversion results, It is conclude that if upper coalgoaf is low resistivity, inversion result of the bodies below down the upper goaf willbe affected by low resistivity shielding, and the inversion result is not very well forhigh resistivity bodies, furthermore, when two groups of coal seam have enoughspacing for exploring double low resistivity of coal seam, for lower one with lowresistivity, the inversion result can show anomalous bodies clearly. Finally, theconclusion is proved by forward modeling and inversion with real data example. Theadvantages and disadvantages of exploring coal goafs using transient electromagneticmethod are evaluated.To sum up, better coal goafs result can be obtained by collected materials fully,analyzed the affecting factors of results comprehensively, tidied up the data, adjustedthe parameters, processed and interpreted data.