格子型ハイダムの土砂コントロール機能を評価するための水理模型実験

摘要

Much of the experimental and numerical research on sediment control by open-type check dams tries to take into account the continuity of sediment routing from upstream to downstream reaches of the river basin. For example, the minimum grid size of the grid-type check dam, which is a type of open-type check dam, can be experimentally set to d_(ss) of sediment, which is based on the size distribution of bed material and flume data as determined for a straight, open channel.rnIn the case of a high check dam constructed in a curved ravine, the effects of curved flow and bar formation on sediment deposition in the storage area are supposed to be significant. A plan for constructing grid-type check dam with heights around 20 m can be newly proposed in a basin. In the main river with a reservoir in a basin at the downstream reach, previous heavy rainfall events may result in a huge amount of sediment deposited in the upstream reach through numerous torrents. Sediment transportation should be controlled to prevent huge amounts of sediment from moving to downstream reaches. Additionally, the main flow has many curved reaches. Therefore, sediment load passing through check dams in flash floods should be reduced as much as possible and, however, higher amounts of sediment should be transported in small sized floods.rnPresent study discusses preliminarily the effects of bed configuration on sediment control function in a check dam using experimental data obtained by hydraulic model tests such as sediment runoff rate from check dam, bars induced channel shifting, longitudinal and cross sectional bed profiles, temporal changes of mean diameter and sediment concentration passing through the check dam.%透過型砂防えん堤による土石流の土砂捕捉に関する研rn究は，主として，勾配の大きい直線水路を用いた実験デrnータを用いて数多く行われている。これらの幾つかrnの研究成果を参考にして，例えば，土石流・流木対策のrn指針解説では，格子型砂防えん堤の格子の最小間隔の目rn安が河床材料の95%粒径の1.0倍と紹介されている。