Research On Principle Of Storm-water Pipeline Sediment Accumulation And Erosion Based On SWMM

At present pollutants in almost all urban drainage is deposited in different degree.Drainage sediment deposition will not only lead to corrosion pipes and reducingflow-carrying capacity, but also pollutants in sediment will be released into receiving waters,which can be a serious threat to the receiving water environment.Therefore, for preventingand reducing the urban water pollution and ensuring the sustainable development of urbanwater environment, drainage sediment deposition and washoff must be researched deeply,which has been one of the most important urgent tasks for urban water environmentmanagement.In this paper, the EPA SWMM model is used as an auxiliary tool. Through the field testand model calculation, the drainage sediment deposition and washoff law and pollution loadare reseached under different rainfalls. Through the reseach, it can provide data support forpipeline dredging and reduce pollution of receiving water by drainage sediment.The main conclusions in this research are as follows：(1) Through the comparison of the relationship of rainfall and single rainfall runoff SSload received by the experimental method and SWMM simulation method, the relevantwater quality parameters in SWMM can be adjusted manually so that rainfall and singlerainfall runoff SS load relationship would be approximate anastomosis in the above twomethods. Until now the parameters are suitable for typical water quality parameters inSWMM, which are the fundamental in water quality.(2)Through Chegongzhuang Street and Wudongdalou area simulated by SWMM, therelationship between SS accumulated load of drainage sediment and different factors can beobtained under different return periods. And further by the correlation analysis of SPSSsoftware, the main influence factors of SS accumulation are got. The factors contain rainfall,boundary shear force, sediment-carrying capacity of flow and rainfall intensity.(3) Through the main factors of influence drainage sediment accumulation obtained, theexperience function between SS accumulated load and rainfall, boundary shear force andsediment transport capacity can be obtained in multivariate nonlinear regression by SPSS. Bythe experience function verificated, it is shown that when surface area and pipeline diameterare changed under different return periods, the relative error of SS cumulative loadcalculation and SS cumulative load simulation value is changed very little. Therefore, theexperience function of SS accumulated load of drainage sediment is certainly reliable.(4) Through the experience accumulated function of drainage sediment established and simulated by SWMM, conclusion can be obtained as follow:①The relationship betweennearly30years return periods of rainfall and SS accumulated load in Chegongzhuang Streetarea is shown that when return period of rainfall is less than0.376, SS accumulated load isincreased with return period of rainfall increasing and when return period of rainfall is morethan0.376, SS accumulated load is gradually reduced with return period of rainfall increasing,but SS accumulated load is more than90mg/m~2, occupied69.03%of total SS accumulatedload. Therefore, for the old residential areas, accumulated pollutants in pipe should be mainlycontrolled in rainfall of more than25mm (The return period is0.376).②The relationshipbetween nearly30years return periods of rainfall and SS accumulated load in Wudongdalouarea is shown that when return period of rainfall is less than0.276, SS accumulated load isincreased with return period of rainfall increasing and when return period of rainfall is0.276,SS accumulated load is reached the maximum for29.0186mg/m~2, after then SS accumulatedload is gradually reduced with return period of rainfall increasing. when return period ofrainfall is less than0.276which is less than20mm in rainfall, SS accumulated load isoccupied69.03%of total SS accumulated load.Therefore, for new residential areas,accumulated pollutants in pipe should be mainly controlled in rainfall of more than20mm(The return period is0.276).(5)Through Chegongzhuang Street and Wudongdalou area simulated by SWMM, therelationship between SS washoff load of drainage sediment and different factors can beobtained under different return periods. And further by the correlation analysis of SPSSsoftware, the main influence factors of SS washoff load are got. The factors contain averageshear stress, maximum flow, maximum rainfall intensity and average rainfall intensity.(6)Through the main factors of influence drainage sediment washoff obtained, theexperience function between drainage SS load and average shear stress, maximum flow,maximum rainfall intensity and average rainfall intensity can be obtained in multivariatenonlinear regression by SPSS. By the experience function verificated, it is shown that whensurface area and pipeline diameter are changed under different return periods, the relativeerror of drainage SS load calculation and drainage SS load simulation is changed very little.Therefore, the experience function of drainage SS load of drainage sediment is certainlyreliable. After then combined with the function of ground SS erosion load provided bySWMM and accorded to the system in the balance-pollutants calculation method, theexperience function of SS washoff load is obtained.(7) Through simulated by SWMM and the experience function of SS washoff loadobtained, the relationship between nearly30years return periods of rainfall and SS washoffload in Chegongzhuang Street and Wudongdalou area is reached. It is shown that whether for old residential areas or new residential areas, when return period of rainfall is less than0.376which is less than25mm in rainfall, SS washoff load are occupied69.03%of total SSwashoff load. So sediment load flushed and released in little rainfall event is great impact onreceiving water. Hence, sediment erosion caused by less than25mm rainfall should becontrolled, which is more practical significance to receiving water.(8) By drawing on the existing foreign sewer sediment control measures or techniquesand combined with the drainage characteristics of Beijing, three sediment control measuresare proposed in these reseach. They are source control, midway control, end control.