Research on Inductance Effect Removing for Mine TEM with Multi Small Loops

摘要

Small loops TEM method is widely used for water detection in underground coal mine in the past few years.However,the self and mutual inductance effect of multi-loops distorts the early time channel very badly,and the instinct transition area of small side-length loop upraises the signal of late time channel,both of which will disturb the accuracy of data processing and interpretation.In order to solve those problems,two steps are given to eliminate the effect of small loops by analyzing the difference between underground mine TEM curves and ground TEM curves.Combining the relationship between inductance formula of multi-loops by analytical derivation and derivative of current-time by actual measurement,the effect of small loop on early signals could be removed by calculating the inductance electrodynamic potential that should be eliminated.Introducing the definition of curve offset,utilizing the relativity between the slope of attenuation curve and the exponent term of time,taking forward modeling curve as the fitting target,the influence of loop's instinct transition area on late signal could be corrected in a certain extent.By processing of a large amount of practical data from different types of mine water detection and comparing with other actual geology information from drilling exploration,the method is proved to be effective for achieving good data for accurate inversion and interpretation.It permits no more introducing of experimental parameters into the processing of mine TEM data,and it is a fast and practical method,it is worth further study in theory.