The Quality Simulating Studies Of The Waterway Dredging’s Impact On Water Quality

In order to maintain the navigating standards of waterway and improve thesediment deposition conditions, it is necessary to dredge the waterway at regularintervals. However, suspended sediment may be generated easily from agitationand leakage in the process of construction, which may increase the turbidity ofthe constructing areas as well as its surroundings. Meanwhile, the silt carried inthe poisonous and harmful substances will also decrease the use of the waterquality. From this prospective, in the evaluating process of the dredging’senvironmental influences, certain sediment water quality model should beselected according to the different waters and the characteristics water pollution.For dredging suspended pollutants caused by the influence of range forecast andevaluation, choosing the right desilting scheme is very necessary. In addition, itis of great significance to water environment protection and the development ofgreen dredging.This article is based on the FLUENT software to simulate the sedimentsuspending diffusion conditions of the engineering area. It is based on the thenumerical simulation prediction results, analyzing and comparing two kinds ofdredging (grabbing and cutter suction) in different dredging periods (flood anddrought period).From the analysis of suspended sediment concentrationdistribution and diffusion area, the best construction scheme is obtained. Throughthe overflow reclaimed pool sediment settling process simulation andcomparative analysis of sediment settling effect as well as sedimentconcentration under different inlet velocity, the settlement law of sedimentparticles is acquired.The researching results prove that: through two kinds of dredging’s(grabbing and cutter suction) influence on construction of flood and droughtperiod of suspension diffusion in constructing area, the direction ofthree-dimensional selected monitoring cross section in the construction of thedrought period of sediment concentration is lower than the flood season. On abasis of a dredging, and according to the dredging operation trajectory sourceafter superposition and through the comparing area of the spread of the super water quality standards, it is revealed that the flood season is much higher thanthe drought season. The respectively practical use of two kinds of forms ofdredging operations indicate that the construction of sediment suspensiondiffusion in flood season’s influence on the waters surrounding is bigger than thatof drought period,that is to say,drought period is the best dredgingperiod.According to two kinds of forms of dredging under the maximumsediment concentration in each monitoring section optimum construction periodand average area concentrations of contrast analysis,the selected monitoringsection z=10、20、30、40、50. The grabbed method’s the maximum sedimentconcentration or regional average concentration are both higher than cuttersuction method. In the selected monitoring section of y=-9、-7、-5、-3、-1andx=14、13、12、11. Since the cutter suction’s venting source is bigger than grabbedmethod, the nearby source of dredging point y=-9and x=14the grabbed dredgerdredging sediment concentration is lower when compared to the maximum ofcutter suction. The rest of the monitoring cross section from a maximumsediment concentration or regional concentration were greater than the averagedrag type dredging methods, namely the cutter suction is the best form ofdredging.Method based on FLUENT software simulates the sediment settling processfor cutter-suction dredge mud treatment structures under the overflow cofferdamin the pool and take four alternative flow velocity.It takes comparing analysis tosediment subsidence effects without the inlet velocity and sediment concentration.It turns out that with the decrease of imported water flow velocity, sedimentationtanks of the density current, short-circuiting phenomenon is more serious,leading to sediment particles settling effect affected by poor water quality; inletflow velocity increases, the sedimentation tank into strength of density flowoutlet at improving, but sedimentation tanks HRT shortened precipitation effectwill be affected. So in the inlet flow rate selected should be considered above twofactors, both to reduce the impact on the density current flows from the state, theneed to increase the pool of sediment particles theoretically HRT, to essentiallythe effect of improving the settling of sediment particles.This study has a strong target which provides the theoretical support for thedredging project of The Yangtze river.It also provides the technical support forthe research of the green constructing technology of the three gorges channel. The research has important existing use value and practical significance.