| 摘要 |
PROBLEM TO BE SOLVED: To obtain large water-cut-off effect by curvedly infiltrating a water-tight apparatus such that a packing piece constituted of a foam body is consolidated onto an internal wall of a cave hole and a packing piece constituted of an elastic body such as a rubber plate is press-contacted to a shielding machine main body. SOLUTION: A first packing piece 2 is constituted of an elastic body such as a rubber board, and a second packing piece 3 is constituted of a flexible foam body such as sponge rubber, which pieces are both annularly formed and attached to an entrance cave hole 10 so as to be in close proximity to a rear portion 10a and a front portion thereof. The second packing piece 3 is consolidated onto an internal wall 10b of the cave hole, and the first packing piece 2 is press-contacted to a shielding machine main body 20. When the shielding machine main body 20 is thrust from the entrance cave hole 10 to carry out excavation, the first and second packing pieces 2, 3 are simultaneously forcedly bent in the frontward direction to be curved, and therefore they are in sliding contact with the periphery of a cylindrical portion of the shielding machine main body 20 due to the elastic force of the pieces. Thus, formation of a small gap can be completely avoided, to thereby obtain large water-cut-off effect.
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