Model Design And Experimental Study On Water And Sedimentation Of Meandering River For Qianxi City Section Of Luan River

The bend is an important element of natural river, and always exist extensively atmontane and plain river especially alluvial plain. The bend water currently is function bygravitational force and centrifugal inertia force. Motion characteristics of water flow andsediment in bend reach are different from that in straight stream by cross current andtransverse gradient of water surface, the water structure is very complex. At the same time,the concave bank of bend is cut by the water current, so there is the danger of the riverbank collapse or degradation, and bend is the important object in the river improvementengineering. Thus, the studying on the motion characteristics of water flow and sedimentin bend reaches is valuable in theory, and realistic signification.The bend shape like a "U", and have an ait in the QianXi river reach of Luan River.Now the flood control capacity of this reach can't reach tenth, the planning project willhold the ait, carry on a ecosystem construction and build two overflow weirs for adjustingriver slope. The water current is not only controlled by bend but also influenced by the aitand hydraulic structure when it's passing by, that makes the river reach more complicatedcomparing with general bend.The physical model of river engineering can repeat the evolution of the natural riverwithin the scope of certain space and time, or forecast the development trend of thefinishing engineering. It is a not replaceable method to resolve three-dimensional problemsor instances including hydraulic structure in the test area, operator in water conservancyalways attach widespread importance to the river model. This paper studied on the bendreach regulation works of Luan River in QianXi county, and has researched on the motioncharacteristics of water flow and sediment in bend reaches according to the physical modelof river engineering, the main conclusions are as follow:(1) The information of hydrology and bedload about antetype riverway is analysed,catch the nature of questions, and choose the model of the similar rule in reason. To thecomplicated bend, this paper choose tentatively that the model distortion ratio is 2.4,through the model verification and the rationality result of test, we know that the influenceof distortion ratio is limited and satisfy the request of this test; Based on analysing thecurve of bedload match about antetype riverbed, and choose nature sand which iseconomical and logical for the model through thinking over the question in more aspect, italso avoid a series of problem which is caused by using gentle send. (2) According to researching the motion characteristics of bend water flow withdifferent discharge conditions, conclusions are below: the maximal transverse gradient ofbend water surface turned up at the top of the bend nearby, Along with the augmentation ofthe discharge, the generant position would remove to the upstream; the maximal flowvelocity would Along with the aggrandizement but the aggrandizement of the dischargeduring the bend reach, and the generant position would remove to the downstream.(3) The ait has the functions of backwater and distributary for bend water flow. Theinfluence of the ait is obvious when the discharge is small, the transverse water surfaceprofile is a saddle type, i.e. the center is high and two ends is low. The influence of the aitwill trail off when the discharge become large, the transverse water surface profile isinclination, more gently in the concave bank and more steep in the convex bank. Thediversion ratio of the ait two side is not change with the variety of the discharge.(4) The deposition and erosion of sediment in bend was researched with differentdischarge conditions, the results: the bend discharge escaped from the main channel walland appeared turbulent motion in the joint of No. lweir's nearside and bottomland. Alongwith the aggrandizement of the discharge, the turbulent motion becomed acute, theflushing also becomed worse, and had the different degree deposition in the downstream ofNo. lweir. The small discharge flushed the side slope of the ait badly, the sediment existsthe small transverse transportation at the time of the large longitudinal transportation; Theait was flushed obviously at the whole after big discharge, the sediment pushes andprogresses to downstream, the transverse transportation is unconspicuous.