Data Processing And Experiments On Transient Electromagnetic Method With A Conical Source

The small multi-turn coils is the typical transmitter loop for transient electromagnetic method used in underground limited space,such as coal mine roadway,engineering tunnel and shallow detection,etc..The multi-coil with an overlapping way makes the mutual inductance increased and turn-off time longer,and eventually,the shallow "blind zone" enlarged.Hence,studying the technique of decreasing “blind zone” has a very importance mean in geophysical prospecting.This paper studied the transient electromagnetic response with seriously concerning the early and late stages and turn-off time effect.Meanwhile,the mutual inductance of a conical source proposed by our project was considered as a key point,the result on which shows that,the mutual inductance coefficient for conical source is much more less than that for multi-coil,and even reaches to one order.We made several experimental equipments for field tests,and carried out them on surface and in coal mine roadway.The surface experiment results indicate that the same channel response excited by normal and inversed cones is similar to that from traditional multi-coil.Combining the known information and the result of high density resistivity method,both of the cones have an ability to locate the geological anomalies,however,the effect of the normal cone is definitely better than that of the inversed cone.The conical source was turned to have a great potential to be a sensor,and also has a good adaptation to use in the limited spaces.