| 摘要 |
<p>PURPOSE: To accurately measure the depth of any highly permeable part of a bedrock which may become a course of water. CONSTITUTION: First and second boreholes 11, 12 are provided inwards from the surface of the ground, and an alternating current is supplied between a first current-carrying electrode 13 inserted in the first borehole and a second current-carrying electrode 16 inserted in the second borehole. Third and fourth electrodes 14, 15 for measuring potential differences are provided, respectively, in positions above and below the first electrode inserted in the first borehole and are combined to provide a combination electrode. As the depths of the electrodes are varied, a potential difference is measured from the voltages detected from the third and forth electrodes, and changes in water permeability of the ground are measured from changes in polarity of the potential difference.</p> |
