Effects of freezing and thawing cycles on over-consolidated reconstituted structural loess

Abstract

The effect of freezing and thawing cycles on the behaviors of over-consolidated reconstituted structural loess was studied by routine uniaxial compression tests and uniaxial loading-unloading cyclic tests in this paper. Energy dissipation was used as a new way to investigate the structural damages during the freezing and thawing cycles. The change laws of strength, failure strain, modulus and the energy dissipation after different freezing and thawing cycles were investigated. It was found that under the experimental conditions used, freezing and thawing cycles lead a slight expansion in volume, and an obvious desiccation of the specimens. The failure strain and initial tangent modulus decreased gradually with freezing and thawing cycles, while the average resilient modulus decreased significantly after the first cycle, and then appeared impervious to a further increase of cycles. And based on that fact, the threshold value of Su1.0% for the over-consolidated reconstituted structural loess was suggested as about 225 kPa or a little higher. The UC strength decreased most intensely after first 3 cycles and then recovered a little during the 5∼10th cycles, which indicated a slight re-structuring effect during the cycles. The change trend of strength with freezing and thawing cycles was similar to that of the average energy dissipation, which further verified the structural damages induced by freezing and thawing cycles. The evolution laws of energy dissipation with axial strain could be described by parabolic curves, and the vertex of the fitting parabola usually appeared around the failure strain under various freezing and thawing cycles.