Influencing factors and significance of the skewness coefficient in grain size analysis
粒度分析中偏度系数的影响因素及其意义

The coefficient of skewness is an important parameter for the analysis of sediment gain size, which is vital to identify sediment under different transported dynamic and depositional environment. Based on the study of connotation of skewness and comparison of different methods of gain size analysis, the skewness is found to be a slanting asymmetry in an abnormal distribution, which sensitively reflects the trace variation of the grain size distribution. The positively biased is the grain distribution skewed to the segment of fine grain, while the negative skewness slants to the coarse grain. The positive or negative and the big or small values of the skewness are related to many factors, they are controlled by sediment property of not only sedimentary environment but also the balance of grain size and ambient energy, as well as the influence of human factors, including calculation and testing method. Sieve analysis combining graphic method is appropriates for the coarse grain when grain size span is large; laser grain analysis uniting moments method is appropriates to the grain size analysis of silt-clay sediments.