水叩き下流護床工の石礫間詰めによる落差工下部パイピング対策の研究

抄録

Bed protection works are constructed for protection of local scour and as energy absorber in downstream of falling works. If hydraulic gradient in bed material were over standard value, seepage control seat would be designed for piping under the falling works. The hydraulic gradient is estimated by use of difference of water levels in upstream and downstream of the river crossing structures. But the hydraulic gradient may increase by bed deformation in down stream of the river crossing structures after the construction. And in the case of low density of concrete blocks of bed protection works, pressure would come down by separate flow in the downstream end of apron.
In this paper, it is examined that causes of piping under falling works and countermeasures of gravels among bed protection works in downstream of apron by large-scale hydraulic experiment.