中文摘要：

在坑道超前探测方法中，直流电阻率法原理和操作简单，应用前景广阔，其中侧向聚焦电阻率法应用在测井中已经成为一种常用方法．本文研究了三维坑道直流聚焦法电极组合，首先计算分析了两个同性点电源的电流分布规律，指出由于电流的相互排斥作用，电流密度在这两个点电源的中垂线下一定深度处产生最大值，这个深度与这两个点源之间的距离成正比．基于上述原理，设计出三种电极组合：四点电源、五点电源和九点电源布极方式．其次，用三维有限单元数值模拟的方法计算了上述三种电极系的空间电位分布，得出九点电源方式对电流聚束效果较好，而且当主电极电流小于屏蔽电极电流时效果最好．

英文摘要：

In the tunnel forward detection methods, DC resistivity method has a good application prospect because of its simple principle and operation, and lateral focused resistivity method has become a commonly used method in well logging. This paper studies the electrode combination of 3D tunnel DC focused method. At first, the authors calculate and analyze 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 proportional 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 focusing effect. Furthermore, when the main electrode current is less than the shield electrode current,the focusing effect is the best.