潮滩悬沙粒度参数的动力沉积学意义

THE DYNAMIC SEDIMENTOLOGICAL MEANING OF GRAIN-SIZE PARAMETERS OF TIDAL FLAT SUSPENDED SEDIMENTS

根据1983年10月和1984年5月两次大潮期悬沙粒度和流速的同步观测资料及细颗粒泥沙动水絮凝沉积试验成果，分析悬沙粒度参数的动力沉积学意义。结果表明，在以细颗粒泥沙絮凝临界流速（21cm／s）为界的两组悬沙样中，悬沙偏态系数和小于4．0μm拉级悬沙的百分含量在散点图中有显著分离；中值粒径和峰态系数有一定的分离；分选系数和大于16μm粒级是沙的百分含量几乎无分离；但中值粒径、分选系数、偏态系数和大于16μm粒级悬沙的百分含量有良好对应关系。粒度参数的变化是悬沙动力沉积特性的反映，其中偏态系数、中值粒径和分选系数的变化可以作为判别单颗粒沉积与絮凝沉积的依据，峰态系数的变化则较复杂，应用时须十分慎重。

Based on Oct., 1983 and May, 1984 synchronically measured sediments and tidal flat velocity data and the floc-depositional test data on fine sediments in flowingwater, the dynamical sedimentological meaning of grain-size parameters of suspendedsediments is analysed. The results show that there are significant separation in theplot of skewness to < 4.0μm grain-size percentage content, a certain separation inthe plot of median to kurtosis and almost no separation in the plot of the standarddeviation to > 16μm grain-size percentage in two suspended sediments groups dividedaccording to the cridcal flocculation velocity of fine sediments; but that there aresignificant correlations among the median, standard deviation, skewness and > 16μmgrain-size percentage content. The changes of grain-size parameters reflect the characteristics of dynamical deposition of suspended sediments among which skewness,median and standard deviation may be used as the criterions to decide whether thesuspended sediments settle as single grains or in floc forms; but the changes of kurtosis are extremely complex and should be careful used.