The research on electrode systems of 3D tunnel DC focused method

摘要

In the tunnel forward detection methods, DC resistivity method will have a good application foreground because of its simple principle and operation, and lateral focused resistivity method has become a method in well logging use. This paper studies the electrode combination of 3D tunnel DC focused method. At first, the authors calculate and analyse the current distribution of two point power sources with the same electrical property, and indicate that as currents exclude each other, current density has a maximum at a certain depth along the perpendicular bisector of the two point power sources and the depth is directly proportion to the distance between them. Based on the above reasons, the authors work out three kinds of electrode combinations: four-point power source, five-point power source and nine-point power source. In addition, the spacial potential distributions of the three kinds of electrode systems are calculated by 3D FEM,and we can find that the nine-point power source mode has a good current focused effect. Furthermore, when the main electrode current is less than the shield electrode current, the focused effect is the best.