流域物质与水系及产沙间非线性关系实验研究

An Experimental Study on Influence of Materiel Component to Non-linear Relation between Sediment Yield and Drainage Network Development

在 35.56mm/ h·cm2定雨强的人工降雨条件下 ,组成物质中径分别为 0 .0 2 1 mm、 0 .0 66mm及 0 .0 76mm的流域发育对比实验表明 ,产沙过程具有波动振荡衰减特征 ;水系发育以增加河道 (沟道 )数目及弯曲拉伸长度两种方式进行最小消能。水系分形维数正是这种消能的量度。水系分数维值随时间呈不对称上凹型曲线。对比分析表明 :产沙过程的振荡性、衰减率 ,随物质变粗而加强 ,水系河道数目随物质变细而增多 ,河道随物质变细拉长 ,分数维值与产沙间是不对称双曲线的非线性关系。曲线的递变率绝对值随时间推移和物质变细而变小 ,体现状况代替时间特征。

In this paper an experimental study on influence of materiel component to non linear relation between sediment yield and drainage network development has been completed in the Lab of Fluvial Geomorphology in the Institute of Geography, Chinese Academy of Sciences. The area of flume drainage system is 81 2 m 2, the longitudinal gradient and cross section slope are from 0 0348 to 0 0775 and from 0 0115 to 0 038, respectively. Different model materials with a medium diameter of 0 021 mm, 0 076 mm and 0 066 mm cover three experiments for each. At the beginning the ψ shaped small network is dug in the flume, an artificial rainfall equipment is a sprinkler system composed of 7 downward nozzles, distributed by hexagon type and a given rainfall intensity is 35 56 mm/hr·cm 2. Three experiments are designed by process response principle. Running time spans are 720 minutes, 1 440 minutes and 540 minutes for Run Ⅳ, Ⅵ, and Ⅰ respectively.\;Three experiments show that the sediment yield processes are characterized by delaying with a vibration. During network development the energy of a drainage system is dissipated by two ways, of which one is increasing numbers of channel (rill and gully), and another one is enlarging the channel length. The fractal dimension of a drainage network is exactly an index of energy dissipation of a drainage morphological system. Change of this index with time is a unsymmetrical concave curve. Contracting three experiments explains that the vibration and the delaying ratio of sediment yield processes increase with material carousing, while the number of channel decrease. The length of channel enlarges with material fining. There exists non linear relationship between fractal dimension and sediment yield with an unsymmetrical hyperbolic curve. The absolute value of delaying ratio of the curve reduces with time running and material fining. It is characterized by substitution of situation to time.