Study On Mechanics Of Gravel Movement In Minjiang River

In this paper, gravel characteristics and variety along the river were studied with digital image technology; variety of grain sizes distribution of the river bed along Jinmahe section in Minjian river was analyzed; several representative formulas of bedload transport rate were proved according to the field data of Dujiangyan. Following is the main achievements:Firstly, it's the first to analyze gravel characteristics by the digital image technology. According to video-recording in the field and computing by making programs, several gravel parameters, such as perimeter, area, long and short axis etc., were gained and the appearance coefficient and variety along the river were computed. Gravel roundness increased along the river by analyzing the field data in Baishahe River, a tributary of Minjiang River.Secondly, according to the field data in Jinmahe River, variety of gravel size distribution along the river was analyzed. For the scouring and depositing equilibrium stream, the dominating factor resulting in gravel decrescence was stroking, weathering and grinding. Bedload is the main factor resulting in bed form for few sands of suspend load in the river bed. Obviously armoring layer existed in the surface of the river bed.Finally, bedload transport rate of Dujiangyan was computed with several representative formulas. According to the computing result, Einstein Formula was coincidental with the field data, but not so well for Meyer-Peter formula, Bagnold formula, Engelund formula and Yalin formula. Influence relation of non-uniform flow to variety of transport rate was first gained.The achievement of this paper has an important reference value in analyzing the mechanics of bedload movement in the mount river without field data.