Experimental investigation of the path-dependent strength and deformation behaviours of frozen loess

A series of triaxial shear, creep and relaxation tests with different stress paths were conducted on frozen loess at a temperature of -6 degrees C in order to experimentally study the path-dependent strength and deformation behaviours of the loess. Testing results indicate that the strength, the stiffness and the stress-strain relationships of frozen samples all rely on consolidation pressure and the shear stress path. The effects of K0 (0.625-1) consolidation path in the mechanical behaviours of frozen loess are not significant. Triaxial creep and relaxation tests were performed by seven pre-set paths. The rheological behaviours of frozen loess are also sensitive to the stress path. The initial loading process before rheological tests leads to the microstructure damage and anisotropic behaviours of frozen samples, and further dominates the strengthening of the viscosity properties during the creep (stress relaxation) process. Three types of stress history (consolidation, pure shear and couple history) were selected for preloading on frozen samples before triaxial tests to study the influences of the stress history on the mechanical behaviours in detail. The weakening effects of the pure shear history in the soil properties were experimentally verified. The stiffness behaviours of frozen loess are more susceptible to the damage process (prestress history) than the strength behaviours. Due to the competitive influences of the consolidation and shear history on the soils properties, the rheological behaviours of samples are dependent on the specific path history and maximum stress history of the preloading procedure.