风成沉积物3种粒度参数计算方法比较

马茜茜, 肖建华, 姚正毅

A comparative study on the three calculation methods of grain-size parameters for aeolian sediments

Xixi Ma, Jianhua Xiao, Zhengyi Yao

表1 图解法和矩法粒度参数计算方式

Table 1 The formulae of grain-size parameters for graphical-method and moment-method

粒度参数	Folk-Word图解法^[10]	McManus矩法^[11]	Friedman矩法^[13]
平均粒径	$M_{z} = \frac{Φ_{16} + Φ_{50} + Φ_{84}}{3}$	$M_{z} = \frac{\sum_{i = 1}^{n} X_{i} f_{i}}{100}$	$M_{z} = \frac{\sum_{i = 1}^{n} X_{i} f_{i}}{100}$
分选系数	$σ = \frac{Φ_{84} - Φ_{16}}{4} + \frac{Φ_{95} - Φ_{5}}{6.6}$	$σ = \sqrt[]{\frac{\sum_{i = 1}^{n} {(X_{i} - \overset{ˉ}{X})}^{2 ?} f_{i}}{100}}$	$σ = \sqrt[]{\frac{\sum_{i = 1}^{n} {(X_{i} - \overset{ˉ}{X})}^{2 ?} f_{i}}{100}}$
偏度	$S K = \frac{Φ_{16} + Φ_{84} - 2 Φ_{50}}{2 (Φ_{84} - Φ_{16})} + \frac{Φ_{5} + Φ_{95} - 2 Φ_{50}}{2 (Φ_{95} - Φ_{5})}$	$S K = \sqrt[3]{\frac{\sum_{i = 1}^{n} {(X_{i} - \overset{ˉ}{X})}^{3} f_{i}}{100}}$	$S K = \frac{\sum_{i = 1}^{n} {(X_{i} - \overset{ˉ}{X})}^{3} f_{i}}{100 σ^{3}}$
峰度	$K_{g} = \frac{Φ_{95} - Φ_{5}}{2.44 (Φ_{75} - Φ_{25})}$	$K_{g} = \sqrt[4]{\frac{\sum_{i = 1}^{n} {(X_{i} - \overset{ˉ}{X})}^{4} f_{i}}{100}}$	$K_{g} = \frac{\sum_{i = 1}^{n} {(X_{i} - \overset{ˉ}{X})}^{4} f_{i}}{100 σ^{4}}$