为增加直流电法水平勘探深度，准确查明掘进前方异常体的具体方位，减少机电设备、轨道、地形起伏、电磁干扰等因素对探测结果的影响，开展了直流聚焦多点电源探测聚焦与偏转效应正演模拟。据聚焦电法探测机理，采用有限单元法对空间多点电源场各节点电位进行求解，并推导空间场的电场线微分方程。利用COMSOL软件建立三维地电几何模型，通过改变屏蔽电极与主电极发射电流强度，对不同异常地质情况下的空间电流场聚焦分布特征及电位变化百分比曲线变化规律进行有限元数值模拟。结果表明：聚焦效应探测可增加掘进工作面正前方空间电场线的分布密度，使异常体探测会更加敏感；当掘进工作面正前方存有异常体时，聚焦效应相比无聚焦效应探测效果较好，至少可增大50%的探测距离，且随着屏蔽电流增大，探测效果越好，但对至掘进工作面18 m外的异常体探测效果变化不大；当异常体为低阻体时，电位变化百分比的值为负，反之为正；当异常体偏离坑道中心轴线时，探测效果随着偏离距的增大逐渐变差，此时通过改变屏蔽电流大小使探测电场进行偏转扫描探测，依据主电极四周各方位测量电极的电位变化百分比的变化规律确定出异常体的具体方位。

In order to increase the horizontal exploration depth of direct current method，find out accurately the specific direction of the abnormal body in front of the tunnel face，and reduce the influence of electromechanical equipment，track，terrain fluctuation，electromagnetic interference and other factors on the detection，forward modeling of focusing and deflection effect of detection with DC focusing multipoint current sources were carried out. According to the detection mechanism of the focusing electric method，the potential values of multi-point power sources in tunnel is solved by using the finite element method，and the differential equation of the electric field line of the space field is derived. We can build a three-dimensional geoelectric geometric model with COMSOL，then change the emission current intensity of the shield electrode and the main electrode to simulate the focusing distribution characteristics of the space current field and the change rule of the potential change percentage curve in different abnormal geological conditions by finite element method. The simulation results show that focusing effect detection can increase the distribution density of electric field lines in front of the tunnel face and make the detection of abnormal bodies more sensitive;when there is an abnormal body in front of the tunnel face，the effect of focusing effect detection is better than without focusing effect detection，and the detection distance can be increased by at least 50%,and as the shielding current increases，the detection effect is better,but the detection effect of the abnormal body 18 m away from the tunnel face has little change. When the abnormal body is a low-resistance body，the percentage of potential change is negative，otherwise it is positive. When the abnormal body deviates from the central axis of the tunnel，the detection effect deteriorates gradually with the increase of the deviation distance. At this time，by changing the size of shielding current to detect electric field used for deflection scanning detection，the specific direction of the abnormal body can be determined according to the changing rule of percentage of potential change of the measuring electrode in all directions around the main electrode. This research is of great significance for interpreting accurately the data of the specific direction of the abnormal body and creating the exploration technology of focusing electric method.

0 引言

1 构建聚焦多点电源探测地电几何模型

2 空间场有限元数值模拟及电流场分布特征

   2.1 空间场有限元数值模拟

   2.2 均匀介质空间电流场分布特征

   2.3 含异常地质构造空间电流场分布特征

3 异常地质构造探测聚焦与偏转效应

   3.1 聚焦效应探测

   3.2 偏转效应探测

4 结论