| 摘要 |
PURPOSE:To prevent the downstream side from being adversely affected by V-notch phenomenon, by fitting a means for detecting the transformation of a top diaphragm wall, on the V-shaped locally-transformed top diaphragm wall, and by reducing the falling speed according to the signal of the detecting means. CONSTITUTION:When a falling level is detected in the rising state of the diaphragm wall 16 of a rubber weir 14, then an exhaust electromagnetic valve 22 and an automatic falling valve 24 are automatically opened, and exhaustion is performed through a ventilating and exhaust pipe 20, and the diaphragm wall 16 starts falling. When a top diaphragm wall 18 starts being transformed in a 'V' shape, then a bending pressure sensor switch 34 fitted in the wall is turned OFF, and the exhaust electromagnetic valve 22 is closed, and the exhaust speed namely the falling speed is reduced. As the result, excessive stream is prevented from being concentrated on the central section in the direction of the river width, and the river is prevented from being scoured.
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