| 摘要 |
PROBLEM TO BE SOLVED: To form effective water barrier by definitely expanding a water barrier material even when an amount of groundwater is insufficient as in the case of a boring hole of an unsaturated water-bearing layer at a water barrier device for boring hole where the top and bottom of water absorbing expansive barrier material clamped with a water absorbing expansive rubber layer installed in a supporting pipe. SOLUTION: Expansive speed of a bottom rubber layer with the water barrier material 1 clamped between the top and bottom is set to the expansive speed higher than a rubber layer 3 at the upper level, the rubber layer 3' at the lower level is expanded first, by which spring water falling from the above is received, thereby forming a water tank and the rubber layer 3 at the upper level is expanded, and the water barrier material 1 is expanded between the upper and lower rubbers 3, 3'.
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