钱塘江河口细颗粒泥沙絮凝沉降特性研究

STUDY ON FLOCCULATION AND SETTING CHARACTERISTICS OF COHESIVE FINE GRAIN SEDIMENT IN THE QIANTANG ESTUARY

钱塘江口河口上游河流和海域来沙多为细颗粒泥沙,粘性细颗粒泥沙由于其特殊的表面电化学性质遇到强电解质海水而产生絮凝沉降,是形成河口淤积的原因之一。影响絮凝的因素很多,除了电解质,还有泥沙粒径的大小、盐度、含沙量、PH值、温度、有机质含量、矿物成分、水流速度及紊动情况等。本文通过粒度分析、静水沉降、动水沉降等各种实验手段分析钱塘江口泥沙的基本特性,找出最佳絮凝盐度以及泥沙不淤流速等值,初步探讨了细颗粒泥沙的絮凝机理,为治理钱塘江口提供科学依据。

The main reason causing sediment deposition on the water way in the Qiantang Estuary is the flocculation of large amounts of cohesive fine grain sediment from the river and that from the sea, induced by strong electrolyte sea water at the border of sea water and fresh water, and the rapid settling of floes. There are many factors affecting flocculation, such as salinity, grain size, sediment concentration, pH value, temperature of sea water, current velocity, mineral characteristics of sediment, organic material content of sea water etc. According to the information of particle analysis, the composition of artificial sea water, sediments deposition of static water at different salinities and the sediments deposition of dynamic water in the circulating flume, we analyze the basic characters of sediment in the Qiantang estuary. Also we find the optimal flocs salinity and settling velocity. The experiment of dynamic water indicates the influence of current velocity, sediment concentration, salinity and temperature of seawater on cohesive sediment deposition. As a result, the sediments deposition of dynamic water is mainly subjected to current velocity. The flocculation mechanism ofcohesive fine sediment has been discussed, which in turn supplies the necessary scientific information to the study of the Qiantang Estuary.