On characteristics of K0 value and shear behaviour of loess using triaxial test

Abstract Compared with conventional soils, such as sand and clay, little knowledge on the coefficient of lateral earth pressure at-rest ( K 0 ) has been established for loess in the current literature. This paper presents an experimental investigation on K 0 of compacted loess and the associated impacts on undrained shear behaviour. By adopting a K 0 consolidation module in the triaxial system, the K 0 stress state for loess samples was achieved through a unique feedback control. During the K 0 consolidation, the deviatoric stress ( q ) increases progressively with the premise that the volumetric strain ( ε v ) of the sample equals to the axial strain ( ε a ). The results show that the K 0 value of compacted loess is in a range of 0.28 to 0.53, which is dependent on the packing density and the clay content. A distinguishable decrease of K 0 was found in the course of K 0 consolidation for the loosely compacted loess sample, whereas a similar trend was not observed in the dense sample. In the undrained shear stage, all loess specimens revealed contractive response in the stress path ( q - p ’) diagram, which can be quantified by a modified collapsibility index ( I c ). The index is consistently higher for the K 0 consolidated loess samples than for the isotropic ones. The experimental results indicate a strong impact of the initial stress state on the shear behaviour of compacted loess.