|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1995 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1994 : ¥1,300,000 (Direct Cost : ¥1,300,000)
This study aims to establish the hydraulic design of the bed protection works in suit with riverbed lowering downstrem of hydraulic structures.
In this study, three hydraulic experiments, 1) wave type flow over beds of fine gravel, 2) local scour downstream of apron, and 3) local scour downstream of drop-type bed protection works were carried out for the size of fine gravel, d50,3.85mm, the supercritical Froude number, Frl, from 1.7-6.2
On 1) experiment, it is clarified the conditions for occurrence, the characteristics of wave configurations, the scale of the bottom recirculation zone and the charactericstics of velocity distribution of wave type flow.
On 2) experiment, two kind of the scouring investigations were performed under movable bed leveled with apron and mavable bed lowering. The scouring flow is divides into the wave type flow and the repeating periodic flow. The relations between scouring process, profiles of scour holes, maximum depth of scour, capacity of scour and Frl, relative heigth of bed lowering, tail water depth are clarified based on experimental results.
On 3) experiment, the scouring investigatoins were performed by the three type flow, A-jump, B-jump and Wave for the length of drop-type bed protection works, Ld, from 50-150cm. General considerrations on the nature of scour and the characteristics of velocity distribution in scour hohes are clarified. In order to prevent local scour downstrem of drop-type bed protection works, the length of the works should be more than 3.5-4 times of the length of jump roller.