从分界理论和分界阈值等方面,对泥沙分类、球体泥沙沉速、单矿质泥沙、黏粒溶胶、泥沙絮凝、泥沙触变、淤积初始干密度、沙波初始形态、推移质悬移质、床沙质冲泻质等冲积河流泥沙10组分界粒径(分界阈值上界为2.0 mm、下界为0.001 mm)进行了概述,给出了10组分界粒径的特性表和“谱系表”。10组分界粒径的本质核心是粗沙与细沙的划分;基于属性分类方法,10组分界粒径可划分为主要基于泥沙特性(第Ⅰ类),依赖于泥沙与水流两者特性(第Ⅱ类),依赖于泥沙、水流和河床演变三者特性(第Ⅲ类)3种类型;基于确定性分类方法,又可划分为分界意义明确和分界阈值确定(A类)、分界意义明确性较差或者分界阈值确定性较弱(C类)、介于两者之间(B类)3种类型。归纳提出了粗沙与细沙分界粒径、分界粒径与临界流速、泥沙沉速与起动流速等有关河流泥沙分界粒径的讨论问题和研究课题。研究成果提升了河流泥沙分界粒径的系统性和重要性,建立了泥沙“微观”特性与河流“宏观”特性之间的联系。

In line with demarcation theory and threshhold size, 10 groups of demarcating grain sizes of alluvial river sediment with threshhold sizes from maximum 2.0 mm to minimum 0.001 mm are summarized for the first time, and the features and pedigrees of the 10-group demarcating grain sizes are given. The 10 groups involve sediment classification, settling velocity of spheric particle, mono-mineral sediment, clay and suspensoid sol, sediment flocculation, sediment thixotropy, initial dry density, initial sand-wave, bed-load and suspended-load, bed-material-load and wash-load. The essential core of the 10-group demarcating grain-sizes lies in the demarcation between coarse sand and fine sand. By means of attribute-based classification method, the 10-group demarcating grain-sizes can be divided into 3 types: typeⅠ, mainly dominated by sediment features; typeⅡ, relying on features of sediment and flow; and type Ⅲ, depending on features of sediment, flow and fluvial processes. Meanwhile, according to ascertainty-based classification method, the 10 groups can also be divided into 3 classes: class A with definite demarcating meaning and explicit threshhold size; class C with less definite demarcating meaning or less explicit threshhold size; and class B, which is between class A and class C. Finally, issues and further researches associated with demarcating grain sizes of river sediment, such as division between coarse sand and fine sand, relationship between demarcating grain size and critical velocity, and relationship between settling velocity of sediment and incipient velocity of flow, are introduced.The research has helped to improve the systematicness and importance of demarcating grain-size of river sediment and to establish intertink between sediment micro-feature and river macro-feature.