Experimental Study On Formative Patterns Of Branching Reach With Bend

Inland waterway transport is an important part of integrated transport system and the comprehensive utilization of water resources ,which is aslo important strategic resource to achieve sustainable economic and social development in our country.Inland waterway transport compared to other modes of transportion is provided with advantages such as the less areas,the more transport capacity, lower energy consumption, the less pollution ,those of which is particularly evident in the mountains. However, a large number of bending–braided shallows distributed in mountain river not only affect largely coverage and transport accessibility but aslo severely restrict the advantages of inland waterway transport.This thesis is based on the background of western transport infrastructure projects"Mountain River inlet bending mechanism of relaxation and Regulation " ,analyzes the theories of formation modes of inlet bending reach in mountain river from the aspects of river bed topography characteristic,sharp bends braided river,water and sediment conditions and so on. At the same time, the movable-bed sediment model tests in widen river reach are carried out to study the process and pattern formation of bending- widen river reach.Based on the characteristics of the mountain bending–braided reach, this paper divids formation mode of inlet bending reach in mountain river into three types, namely, middle bedrock (reef )forces river braided, relatively stable branching formated by sand bed river sediment, loitering branching, which studies the characteristics of three types of typical river reach including sediment,river and bed evolution. the movable-bed sediment model tests mainly analyze how sediment and grait in the middle of river silt and form relatively stable branching river channel.朗读Accroding to the traction load of the movable-bed physical model experiment,coclusion are made that the flow process, the river bed nodal point morphology and differential height between the left bank and the right bank are the important factors that affect formation and evolution of inlet.By the experment of the traction load of the movable-bed physical model experiment, research is made about the formation progress and pattern of bending–widen–braided reach composed with sediment and grait. In the condition that bed height is about relaxing little paragraph and the left river bed overburden layer is thick, it easily turns into the main channel which lies below the import of low-flow curve concave bank and braided river pattern where is little support on the right bank of the flood of the two branches.In the condition that relaxation of the left side of the river bed is higher and the cover layer is coarse or by the case of bedrock, it's easy to evolve into two situations, the first may form a two braided river pattern which has a small branch of the left bank in flood and divides into braided streams slot and the right bank of the river bend straight main channel in the dry season; the second possibility is to form a two curved convex bank branch river type of which left and right branch split ratio of magnitude is close and waterless main channel is located under the curve raised shore of import.