Experimental Study On The Influence On Turbidity Current Concentration And Deposition Fan Width To Underwater Channel

Debris flow is a natural phenomenon,but also a common geological disasters to people's life and economic construction of caused serious influence.There is debros-flow on land and underwater.Such as the land of mountains and rivers,lakes,sea,water reservoir,there is debris-flow.Underwater landslides is not so easy to be directly observed by people as onshore debris-flow.Underwater debris-flow often derived landslides caused by earthquakes,etc.At the edge of the rivers,lakes and oceans,debris flow directly into the rivers,lakes and oceans.Underwater debris-flow is a potential source of great disasters,such as damage the seabed in the sea cable and offshore facilities,and even cause tsunamis,cause a large amount of sediment deposition in the lake,in the capacity of the hydropower station reservoir sedimentation in sediment reduced,may destroy the hydropower station facilities and also affect the waterway transportation.Turbidity current is a form to influence the underwater sediment movement in rivers,lakes and oceans what is similar as debris-flow,the formation of sedimentary river is the movement of a common phenomenon,and because the turbidity current with the composition of the particles small,itself to the characteristics of gravity flow,so that the movement of the turbidity current underwater distance is longer than the debris-flows,movement range is bigger than debris-flow.Turbidity current mainly exist in the water,so the research of this area is very few,but it should not be ignored:its impact on underwater sedimentary uplifting influence river navigation,near the lake estuary sedimentary,near the mouth of sedimentary shoreline near water entry into the water,within the reservoir sedimentation reduce reservoir,the rise,hollow,with the water inlet,and the Yellow River Xiaolangdi hydropower station reservoir area in our country also repeatedly using the turbidity current desilting.Abound in the southwest mountainous area of reservoir and hydropower station in China,so the motion law of turbidity current,the prevention and treatment of turbidity current hazards,the use of underwater turbidity current motion is critical.Through the analysis of the predecessors'research results,the turbidity current research way by dimensionless analysis combined with laboratory test is the most convenient,direct and effective.Predecessors have already reached the formation of sedimentary type underwater channel conditions:correct turbidity current flow,turbidity current movement of the bottom slope,sediment settling velocity and turbidity current combination of sediment particle size range.In this paper,on the basis of predecessors'indoor experiment,the concentration of turbidity current,accumulation of underwater fan form the influence of the underwater channel width turbidity current movement,mainly draws the following conclusion:?1?the initial volume concentration of turbidity current is introduced into water C₀ 0.03-0.2,underwater channel can be formed;Turbidity current introduction of underwater initial volume concentration C₀ is less than 0.025?don't incloud 0.025?does not contain,not underwater sedimentary type channel.And volume concentration is greater than 0.2 turbidity current is rare in the actual situation,so set the maximum concentration of 0.2.?2?the initial introduction of turbidity current concentration C₀ and dimensionless turbidity current flow Q*,under the combination of formation of underwater channel condition is:0.27C₀+0.03<Q^*<0.27C₀+0.33,and C₀>0.025,only to meet the conditions of combination to form the underwater channel sedimentation.?3?water turbidity current volume concentration C=0.003 is underwater form the lower limit of underwater channel.Underwater sedimentary formation and distance underwater turbidity current is introduced into the mouth of river related to the distance,the farther the distance turbidity current is introduced into the mouth distance,the same water turbidity current volume concentration needed to form the initial introduction of flow channel.?4?water turbidity current volume concentration C and initial introduction flow Q*influence the formation of turbidity current deposit underwater channel condition0.2Q^*>C>0.2Q^*-0.05,;And distance underwater turbidity current export range of 1 to 2m,C>0.005-0.017Q^*to form the underwater channel,3 meters underwater turbidity current lead exports,C>0.02-0.015Q^*form the underwater channel sedimentation.?5?stacking door width and turbidity current exit width than the width of the K value is 20-80?underwater accumulation fan width of 0.5m to 2m L?,can form the underwater channel sedimentation.Smaller when the K value?accumulation fan width narrow L?,after accumulation can affect the turbidity fan on both sides of the terrain,the turbidity of lateral turbidity current shunt reflection,to produce turbulent disturbance turbidity current mainstream line movement,the turbidity of the sediment particles cannot be formed in a relatively short range channel.?6?accumulation is the width of the door width and turbidity current lead exit width ratio K of 20-80?accumulation fan width of 0.5m to 2m L?,the change of dimensionless flow rate Q*,condition of formation sedimentary type underwater channel is:0.06<Q^*<0.027K+1.17,and K>15,can only form are framed within the scope of the underwater channel.?7?the field data into our research model verification,initial introduction of turbidity current concentration C₀ and the combination of dimensionless flow rate Q*,width of K and the combination of dimensionless flow rate Q*and wild rivers into the river,lake and the actual situation of the sea have some sex.And lake,sea,deep and fan contrast experimental data is better,but the wild and indoor measurement differs big,indoor conclusion may not completely suitable for the field.Through the test conclusion,field can be predicted to a certain extent turbidity current sedimentary formation water of river.Rehabilitation of reservoir and hydropower station,the terrain for the prevention and treatment of turbidity current,the prevention and treatment of turbidity current in affect navigable channel sedimentation,reservoir and sand carried out by using the properties of turbidity current to provide theoretical reference.