Application of equivalent inverse flux transient electromagnetic method in shallow karst detection——Taking an area in Longmen County,Huizhou City as an example
The traditional transient electromagnetic method is affected by the transition process of turn-off time and mutu-al inductance,and there exists a large shallow blind area;the newly developed equipotential inverse flux transient electromag-netic method realizes the observation of pure secondary field theoretically and instrumentally,which greatly improves the detec-tion accuracy in shallow areas.In order to study the application effect of isomagnetic inverse flux transient electromagnetic(IATEM)method in the shallow karst detection of 100m,a karst development area in Longmen County,Huizhou City,was taken as the target area to carry out the method effectiveness study,and the main results and conclusions were obtained:(1)The defined soil-rock interfaces and the circled karst development area match well with the known drilling exposure,which verifies the validity of the isomagnetic inverse flux transient electromagnetic(IATEM)method in the shallow karst detection of 100m;(2)Reflects that the karsts in the area have a certain connectivity,the size of karsts is about 1～20 m,and the karsts are mainly developed in the depths of 20～40 m and below 60m.The results of the study have effectively defined the karst de-velopment area in the study area with a depth of 100m and a depth of 60m or less.On the one hand,the results of the study have effectively defined the shallow karst development area in the study area of 100m,which is of great significance for the safe construction of the subsequent bridge project;on the other hand,the equivalent antimagnetic flux transient electromagnetic method has the advantages of convenient construction,efficient acquisition,strong anti-interference,etc.,which is expected to be more important in the future in the field of urban shallow space exploration.
transient electromagnetic methodisomagnetic inverse fluxkarst surveyshallow blind spotLongmen Coun-ty,Huizhou City
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