| 摘要 |
PURPOSE:To raise the durability of a rubber dam by suppressing the circumferential tension of the rubber dam by a method in which the ratio of the circumferential length of the rubber dam to the distance between the fixed lines on upstream and downstream sides is designated to within a specific range. CONSTITUTION:A rubber dam 2 is fixed to fixed lines 3 and 4 on the upstream and downstream sides of riverbed concrete 1. The sectional shape of the dam 2 is varied with changes in the water depths of upstream and downstream sides. When the water depth on the downstream is varied from 0 to H1, the height of the dam is varied from H0 to (H=H0+DELTAH). The rubber dam 2 is so as to meet the relationship 0.30<l/S<=0.40, where S is the circumferential length of the dam 2 and l is the interval between the fixed lines on upstream and downstream sides. The length is of the dam 2 is made larger and the internal pressure of the dam is lowered to suppress the circumferential tension of the dam 2, and also the varying ratio of the dam height with changes in water depth on upstream and downstream sides is made smaller to raise the durability of the rubber dam 2. |
