| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent the accumulation of bubbles to the vicinity of a pressure sensor so that a pressure change can be precisely transmitted to the pressure sensor when a vibration occurs. SOLUTION: A cylindrical filter 12 is set on the bottom part within a boring hole 14 drilled in the ground, and a watertight stand pipe 10 extending from a filter 12 to the ground surface is built, a water permeable material 16 is filled in the clearance between the filter 12 and the boring hole 14 wall, and the upper part of the water permeable material 16 is covered with a water shielding material 18 and buried. A pressure sensor 20 for measuring the head within the stand pipe 10 is integrated to the lower part of the stand pipe 10, and an instantaneous close valve 26 for instantaneously closing the communicating property within the stand pipe 10 when a vibration is detected by the signal from a vibration sensor 28 set on the group is provided between the set depth of the pressure sensor 20 and the general underground water level depth within the stand pipe 10.</p> |
