| The dredging of open water channels is extremely important for maintaining its water delivery capacity and water quality.During the long-term operation of large-scale long-distance open channels,it is inevitable to deposit a large amount of sediment and breed microorganisms in the channels,which affect its water quality and capacity.For example,in the main canal of the middle route of the South-to-North Water Transfer Project,the sediment in the canal must be cleaned up in time under the condition that the bottom mud cannot be naturally washed by the water flow.Moreover,due to the particularity and importance of the main canal of the South-to-North Water Transfer Project,the water cannot be stopped for dredging and the quality of the water cannot be affected during the dredging process.In addition,when the thousands of kilometers of open water conveyance channels are dredging,the site is limited,and small and mobile dredging devices are suitable.Therefore,based on the characteristics of the main canal of the middle route of the South-to-North Water Transfer Project,the research team innovatively designed a set of portable small dredging equipment and proposed a specific dredging plan based on the existing research on aerodynamic erosion and sedimentation.With precision,high efficiency,environmental protection,and airtightness as the purpose of dredging,it serves as a novel solution to the problem of siltation in large and long-distance water conveyance channels.This paper studies the key technical parts of this set of dredging equipment:(1)the law of water and sand movement in the underwater dredging bin and the improvement of dredging efficiency;(2)the flocculation of viscous fine-grained sediment in the sewage flocculation tank of the water system Research on the effectiveness of settlement and water-sediment separation;(3)the force analysis,stability calculation and hydrodynamic model test of the overall dredging system.With the purpose of improving the dredging efficiency of this set of dredging device in the dredging process,it demonstrates its high efficiency(research on the effect of jet disturbance in the underwater open channel dredging bin on the movement characteristics of the sediment and the dredging efficiency),continuity(water The mud output from the dredging chamber of the lower system can be quickly processed on the shore to ensure the continuous dredging state of the work)and stability(force calculation and hydrodynamic model test of the two major working systems on water and under water in a dynamic water environment).Mainly include the following work contents:(1)Research on water and sediment movement law and dredging efficiency in underwater dredging bin.Aiming at the problem of dredging efficiency in the closed cavity of the environmental protection dredging device,the method of combining model test and mathematical simulation is adopted.The experimental analysis is carried out from the blowing area under different pressure,the blowing width of different wind knife spacing,the wind knife arrangement angle corresponding to the dredging effect and the wind knife angle corresponding to different flow,and the arrangement parameters of the components in the dredging bin are optimized.The results show that the wind knife jet is staggered,and the optimal inclination angle is 0°?7°;When the jet time of the wind knife is 10s and the pressure of the air pump of 10 000 W is 0.3×105Pa,the area ratio of dredging in the dredging bin can reach 87.7%.When airflow velocity is 3.1 m/s in the dredging bin,a strong vortex is formed in the dredging bin and the bottom water and sand turbulence are strong,which drives the sediment to move upward to form mud.(2)Flocculation sedimentation and water-sediment separation efficiency of fine-grained cohesive sediment in water system wastewater flocculation tank.Experimental conditions such as static water flocculation sedimentation,ultrasonic assisted flocculation sedimentation and natural sedimentation after ultrasonic assisted flocculation were carried out.The results showed that the ultrasonic wave can delay the flocculation and sedimentation rate of sediment,but the ultrasonic wave can disturb the algae in the mud to float on the water surface.After ultrasonic treatment and natural sedimentation,the sedimentation rate increased,the turbidity at the plain muddy interface decreased,and the compression layer in the flocculation tank was denser.Under the action of the ultrasonic wave,dry and wet bars water content of different layers corresponding to different time is:Wet basic water content Upper>Middle>Lower,dry basic water content Upper<Middle<Lower.Finally,under the same conditions,the effect of water temperature on the flocculation and sedimentation of cohesive fine particles under the action of ultrasonic wave was analyzed.It turned out that the water temperature of 28.6?and 4?will inhibit the height of clear muddy interface of viscous fine particles and the turbidity of the water body,respectively.(3)Through forcing analysis,stability calculation and hydrodynamic model test of integral dredging system.In order to ensure the efficient and stable operation of the dredging equipment,the force analysis,calculation and model experiment of the overall material selection of the dredging system and the force of water flow on the dredging system,such as buoyancy,push force and impact force,were carried out.It is concluded that the buoyancy of the whole dredging system is 50 558.4 N,which is less than the gravity of the whole dredging system 67 557.8 N.Under the common flow rate of 240 m3/s,the design flow rate of 260 m3/s and the increase of flow rate of 320 m3/s,the corresponding three flow rates and the design flow rate(260 m3/s),the corresponding adverse flow rate of 1.76 m/s will not adversely affect the overall stability of the dredging system.Finally,the instability of the dredging system is mainly concentrated at the bottom of the channel when the flow rate is 320 m3/s measured by the spring dynamometer.By installing industrial vacuum suckers on both sides of the dredging bin,it is calculated that the suction force is greater than the sum of the forces of water flow on the dredging system,which meets the requirements of the stability operation of the dredging bin in the hydrodynamic environment. |
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