长江口南槽沉积物粒度的分形特性分析

Fractal characteristics of grain size distribution in the south passage of the Changjiang Estuary

运用分形理论,对长江口南槽沉积物粒度分布的分形特征进行了分析,讨论了沉积物粒度分维值与传统粒度分析参数的关系,指出了粒度分布无标度区分区临界粒径rc的指示意义,提出了用rc来划分悬移质中的床沙质和冲泻质的方法.长江口南槽沉积物样品的粒度分布在大于1.059μm的粒径范围内具有明显的分形特征,分维值的范围在2.384～2.568之间,平均值为2.488;若以粒度分布无标度区的分区临界粒径rc作为悬移质中床沙质和冲泻质划分的临界粒径,则划分长江口南槽悬移质中床沙质和冲泻质的临界粒径在0.954～1.385 μm之间,平均为1.059μm,对应的颗粒的累计质量百分比在4.54%～10.97%之间,平均为8.23%.

Fractal theory is applied to the analysis of the grain size distribution of sediment from the South Passage of the Changjiang Estuary. The relationship between fractal dimension and conventional parameters of grain size distribution is discussed. The fractal scaleless range of grain size distribution is used to divide the bed load and wash load of suspended sediment. The analysis shows that there is obvious fractal characteristics of the grain size distribution of sediment from the South Passage of Changjiang Estuary for particles larger than 1. 059μm. The fractal dimension varies between 2.384 and 2.568 with an average 2.488. The critical diameters are from 0.954 to 1. 385μm （averaged 1.059μm ）if we use the fractal scaleless range to divide the bed load and wash load. The corresponding percentages of sediment less than the critical sizes are from 4.54% to 10.97% （averaged 8.23%）.