The Study On The Flocculation-Propertiesof Cohesive Sediment Suspensions

Colloidal aggregation phenomena are often encountered in cohesivesediment suspensions in which aggregation results from interactions betweenfine particles. This paper presented the preliminary research results on gel-likenetwork formed in hyperconcentrated cohesive sediment suspensions.Firstly, a brief review was given on the recent research of batchsedimentation speed. On this foundation, a new concept---limited floc sizewas brought out. And the mechanical analysis of this limited floc was givenand then, using a iteration method, the speed of batch sedimentation wasfinally achieved. Primary result shows that the academic values are accordantwith the experiment results.Secondly, based on the concept of limited floc size, the thesis putforward a hypothesis, that is, when the gel was formed, the volume fraction ofthe flocs was equal to 1. On this thesis, since we can easily ascertain thelimited floc size, we can easily then get the critical volume fraction was 0.042.This result was quite accordant with the prevenient result.As was known to all, the sedimentation-consolidation curve of cohesivesediment can be split to two phases. The one is equally speed-sedimentation,and the other is compress or consolidation phase. To the former phase, thethesis drew out a equation on the basis of momentum equation. And to theother, the theory and equations used in soil mechanics was used in inference.The result calculated using this model was quite accordant with theexperiment resultFinally, the effects of the container caliber, the container height, thevolume fraction and the sediment properties were researched withexperiments. The experiment result shows that, the batch sediment speeddecreases with the height increases, and decreases with the volume fraction.And, when the mean diameter of the sediment increases, the batch sedimentspeed will increase along. The effects of the container caliber were not tooobvious. When the diameter of the container was small than 65mm, the thebatch sediment speed descends with the container caliber increases. But whenthe container caliber was big than 65mm, the batch sediment speed will keep aconstant.