Research On Grounded Mine Transient Electromagnetic By Numerical Simulation

MTEM is widely used in water prevention and control in coal mines,and is one of the main means of mine geophysical exploration at present.At present,MTEM is mainly used for magnetic source transient electromagnetic method.Confined to the underground tunnel construction space,most magnetic source devices are mainly in the form of overlap or separation of loops with small side length and multiple turns.But there are some technical bottleneck problems,such as: small transmitting magnetic moment,small effective detection distance;The directional detection of geological anomalies is difficult.Difficulty in detecting high resistivity geological anomalies.In the mine transient electromagnetic method with grounded source,a long wire grounded source can be arranged in the roadway space,and the secondary electric field and magnetic field can be received by electrodes or small coils.This method can theoretically overcome the above problems encountered in the practical application of mine transient electromagnetic method with multi-turns and small loop magnetic source.Therefore,this research attempts to grounded source of mines are studied by using numerical simulation method in underground space tem field of law,different azimuth of geologic abnormal body grounded source roadway space metal mine transient electromagnetic response characteristics and noise interference characteristics,for the grounded source of mine transient electromagnetic method,detection methods to establish the system of theory and the development of construction technology and the data processing and interpretation system research theory basis.From Maxwell's equation,we derive the equation which can discretize and calculate the electric field.At the same time,the finite volume method is used to simulate the quasi-static Maxwell's equations in space.The electromagnetic field distribution of magnetic source and electric source transient electromagnetic method in the whole space is compared.Then,in view of the "mirror effect" of the whole space geological anomaly body of magnetic source,the measurement results of magnetic source and grounded source are compared,and it is found that the mine grounded source transient electromagnetic method has better detection direction.Finally,the influence of the low resistivity body in the roadway on the measurement results is compared and studied.The diffusion and distribution of electromagnetic field in full space of mine grounded source TEM is further studied in detail.Considering the mine geological and geoelectric models,such as uniform space field,only low-resistivity abnormal body and only high-resistivity abnormal body,the electric field three components and magnetic field three components in different time periods are calculated respectively,and the comprehensive analysis is made in different planes,and the summary is made to provide help for the establishment of observation methods.The use of a roadway launch a roadway receive(fractional launch reception mode),compared with the electromagnetic field of six components map multiple measuring way,the high and low resistance of abnormal body transient electromagnetic response characteristics,and apparent resistivity of the Ex measuring electric field component transformation and the deep transformation,the apparent resistivity section,and compared with geoelectric model.