| 摘要 |
PROBLEM TO BE SOLVED: To easily detect the existence and a position of damage in an impervious sheet while suppressing an increase in the construction cost of a rainwater storage tank itself. SOLUTION: This rainwater storage tank 10 is buried in the ground via the impervious sheet 20. A surface electrode 38 is arranged outside the impervious sheet 20. A current-carrying electrode 134 and a plurality of measuring electrodes 132 are arranged inside the impervious sheet 20 via rainwater. An alternating current is applied between the current-carrying electrode 134 and the surface electrode 132, and a phase difference between an alternating current and an electric potential difference between the measuring electrodes 132 and 132 are measured in a plurality of places, and a damaged position of the impervious sheet 20 is specified by investigating a change in this phase difference. COPYRIGHT: (C)2008,JPO&INPIT
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