Effect of stress path on mechanical behaviours of frozen subgrade soil

This paper presents a systematical investigation on the mechanical behaviours of frozen subgrade soil under various stress paths. A series of triaxial compression tests under six typical linear stress paths were conducted on artificially saturated frozen samples at a temperature of −6.0 °C by using triaxial low-temperature apparatus (MTS-810). The effects of stress path on mechanical behaviours such as stress–strain (axial and volumetric strain) relationship, failure strength surface, initial stiffness, cohesion and friction angle of frozen sample were analysed and discussed, respectively. The experimental results show that the evolution law of volumetric strain, equivalent cohesion, friction angle and initial stiffness are significantly affected by the stress paths. The plastic deformation stages in stress–strain curves are influenced by the stress paths. The shape and size of experimental failure surface for frozen soil in deviator-mean stress space is not sensitive to the stress paths, but the mean stress at the peak point decreases with the increase of loading angle. Finally, a new nonlinear strength criterion, considering the stress path effect and ‘three stage’ distribution characteristics, is proposed to predict the experimental strength surface of frozen subgrade soil. This failure criterion is capable of giving a good description for the multiaxial failure characteristics of frozen soil in a wide range of loading angles.