【作者】 李富根；

【导师】 杨铁笙；

【作者基本信息】 清华大学 ， 水利工程， 2005， 硕士

【摘要】 随着我国水利工程建设的发展,水库、港口淤积,河口治理和高含沙水流等问题日益突出,对高浓度粘性沙悬浮体系的研究具有十分重要的意义。本文在总结国内外关于浑液面沉速公式的基础上,由极限絮团的概念出发,从力学角度推导出了极限絮团的大小,进而用极限絮团的群体沉速确定了浑液面的沉速。初步的计算结果表明,理论计算结果和试验结果吻合较好。粘性泥沙悬浮体系在初始泥沙浓度达到一定程度的条件下,将形成絮网沉降。作者仍从极限絮团概念出发,并通过对絮网形成机理的研究,假设当絮团体积浓度为1时为絮网形成的标志,从而确定了形成絮网的临界浓度条件。计算结果发现形成絮网的临界体积浓度为0.042左右,与其他研究者的试验结果相吻合。粘性泥沙的絮网沉降(或称整体沉降)过程分为等速沉降和压缩密实沉降两个阶段。对等速沉降阶段,作者从动量方程出发,给出了其沉降曲线的力学方程;对于压缩密实阶段,作者借用了土力学中的次固结理论。初步的模拟结果表明,该模型和试验结果吻合较好,但具体的应用有待于进一步研究。粘性泥沙絮网沉降(或称整体沉降)受到多方面因素的影响,如容器尺度、泥沙粒径和泥沙浓度的影响。作者采用两种不同粒径的泥沙,研究了容器口径、容器高度、泥沙浓度和泥沙粒径对絮凝沉降过程的影响。初步的研究结果表面,容器口径小于65mm时,整体沉降沉速随着容器口径的增大而减小,容器口径大于65mm后,整体沉降沉速随容器口径的增大变化不大,将趋向于一个恒定值;容器高度越大,则整体沉降沉速越小;泥沙浓度越大,整体沉降沉速越小;泥沙中值粒径越大,整体沉降沉速越大。更多还原

【Abstract】 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.更多还原