彎曲水路の河床変動に関する研究

Abstract

The curved reaches in rivers are considered to be structural weak points, likelyprovoking causes of undesirable situations, such as progressing of meanders, bank erosiondue to the local scour, etc. For this reasons numerous experimental researches in labo-ratory and field observations have been carried on. However, the analytical approachfor the mechanics of the sedimentation in curved channel is not established.In the first half of this paper, the processes and the mechanism of the developmentof the local scour are studied on the basis of the experiment of the sediment in the sand'bed and the measurement of shear stress on the rigid bed, which are conducted in twokinds of 1800 curved open channels. The magnitude and the positions of the maximumscour and deposition, the hydraulic characteristics of water surface profiles and thechannel resistance are discussed.In the second half, the theoretical approach for the variation of the lateral bedprofiles with time is developed by the use of equations of continuity for bed load andmotion of fluid in radial direction. The effects of the secondary flow on the bed loadtransport are measured by the motion of particles on the bed, and the modified expressionof Rozovskii's equation for flow direction on the bed is introduced into the above firstequation. The experimental results indicate this approach to be applicable for the initialstage of local scouring.