FLEXIBLE CUT-OFF MEMBER OF BOX STRUCTURE

To provide a flexible cut-off member of a box structure which has a preferable cut-off performance and is less likely to separate from the box structure by water pressure.SOLUTION: When water pressure is applied to a flexible cut-off member 2 from an outer peripheral surface 15 side of a box structure 1, 1, an arcuate part 5 of the flexible cut-off member 2 expands to an inner peripheral face side 14. Then, clockwise angular moment is applied to a right rib 4 and a right insertion part 3, and the right rib 4 is strongly pressed to a right abutting face 13. The right rib 4 is thick and has a high rigidity, therefore, a resistance force acts in a state of the right rib 4 strongly pressed to the right abutting face 13, and clockwise rotation of the right rib 4 is stopped. Accordingly, the right insertion part 3 cannot be drawn out of a right wedge-like groove 12.SELECTED DRAWING: Figure 6 【課題】止水性が良好で、水圧によって箱形構造物から外れにくい箱形構造物の可撓性止水用部材を提供する。【解決手段】箱形構造物１、１の外周面１５側から可撓性止水用部材２に水圧が加わると、可撓性止水用部材２の円弧状部５が内周面１４側に膨張する。すると、右のリブ４及び右の挿入部３には時計方向の回転モーメントが作用し、右のリブ４は右の当接面１３に強く押し当てられる。右のリブ４は肉厚で剛性が大きいため、右のリブ４が右の当接面１３に強く押し当てられた状態で抵抗力が作用し、右のリブ４の時計方向への回転は停止する。従って、右の挿入部３は右のクサビ状溝１２から抜け出さない。【選択図】図６