Abstract: Grain-size distribution curve is one of the most common soil properties. It can help to reduce a large amount of engineering cost if the soil grain-size distribution could be predicted using mathematical equations. Fredlund grain-size distribution equation based on Fredlund and Xing soil-water characteristic curve has proved to be effective for a large number of soil types, while few literatures have been found to verify its effectiveness for loess soils in China. This paper targets on the grain-size distribution of loess soils in 7 regions in the Chinese Loess Plateau, which were fitted with the Fredlund grain-size distribution equation. The results show that Fredlund grain-size distribution equation fits well the grain-size distribution of loess soils in China, with the stable and regularly changing parameters, which presents well the regional characteristics of loess soils in China. The parameters obtained in this paper can be used to predict grain-size distribution of loess soils in these 7 different regions, the results could also provide guidance for grain-size analysis and classification of loess soils.

Key words: loess, grain-size distribution curve, soil-water characteristic curve, unsaturated soils, regional characteristics