貯水池の水を利用した堆砂防止法の研究

Abstract

貯水池堆砂の対策法として, バイパストンネルを用いて流入土砂をダム下流へと排出する方法が既に一部で実用化されている。しかし, トンネルの規模には限界があるため, 流量規模の大きな流域では出水時に排砂しきれない可能性がある。そこで本研究では, 流入土砂を貯水池末端に設けた副ダム上流域に一旦堆積させ, 出水後に貯水池の水を副ダムのゲートから上流側へ逆流させることにより, 堆砂を再度侵食させて排砂する方法について, 水理実験と数値解析による検討を行っている。

Sedimentation in a reservoir has a strong influence on the natural balance of sediment runoff and the function of reservoir. Some kinds of countermeasure such as dredging have been worked out in order to reduce the sedimentation. We propose a new reduction system for sedimentation which is composed of a by-pass tunnel and a sub-dam which is a small dam constructed near upstream end of the reservoir and equipped with a drainage gate and introductory channel. Sediments transported from upstream of a river is caught by the sub-dam during a flood and a delta is formed. After the flood, the delta is eroded by the flow discharged from the introductory channel and the sediment is transported into the by-pass tunnel. Efficiency of the introductory channel is investigated by flume tests. Two dimensional numerical simulation is also carried out to reproduce the experimental results.