軟岩上の限界掃流力と軟岩の洗掘速度に関する実験

摘要

車岩の洗掘速度は，給砂される土砂の粒径によって異なったため，粒径の影響を考慮した軟岩の洗掘速度式を検討した. また，砂礫床上の限界掃流力は等価粗度高さを河床材料粒径とほぼ同程度とすることで良好に評価できるのに対して，上の等価粗度高さ立径に依らず一定値となることが明らかとなった. 本研究で得られた軟岩の洗掘速度及び限界掃流力式により，これまで未解明な部分が多かつた露岩区間の河床変動にっぃて,定量的な検討を行うために重要となる基礎的知見を得ることができた.%The area of exposed soft rocks has been increased due to river bed degradation in the vicinity of Asahikawa City of the Ishikari River. According to the soft rocks have a specific feature in which the local erosion can be caused easily due to high flow velocity, there is a possibility of decreasing the stability of the bridge pier and the shore protection. However, the morphology of sand riverbed and the morphology of soft rock riverbed are different phenomenon, the general bed load transport formula cannot reproduce the bed deformation sufficiently in the area of exposed rocks. In this paper, the relational expression of the erosion rate of the soft rock and the critical tractive force on the soft rock are generated based on the experimental observation.