Influence of grading on the compressibility of saturated loess soils

Abstract

A series of oedometer tests was carried out on natural loess and artificial soils. The loess soils were retrieved from sandy loess, silty loess and clayey loess zones within the Chinese Loess Plateau, as well as Yili area, Xinjiang Province outside the Chinese Loess Plateau. The results show clear influences of grading on soil compressibility. With the finer particle content increasing in loess, the compression paths turn from slightly upwards concave to upwards convex. The collapse index Ic defined in this study increases with the increasing Cu and decreases with the increasing D60. Locations of the soil normal consolidation lines in v–log σ′v plane are also influenced by soil grading characterised by the D60 and Cu. The intact clayey loess has more significant structure effect than the intact silty loess. Compared with the silty and clayey loess, the intact sandy loess has negligible structure effect on soil compressibility. For a given sampling site, deep loess has a higher yielding stress point and is more difficult to compress to the intrinsic compression line than shallow loess, revealing the effect of stress history on the soil compressibility.