Macro–meso freeze–thaw damage mechanism of soil–rock mixtures with different rock contents

Abstract

Soil–rock mixture is a typical discontinuous material and often used as a roadbed filler. Rock content is a key factor in this mixture’s properties. The damage pattern of soil–rock mixtures with different rock contents after freeze–thaw cycles is more complicated than that in normal state. The damage behaviour of soil–rock mixtures with different rock contents after freeze–thaw cycles is analysed in this study. Firstly, size-distributed subgrade coarse grained soil samples with different rock contents (35, 45, 55 and 65%) are prepared. The samples are subjected to freeze–thaw cycles periodically (24 h per cycle) for different times (0 and 10). Large-scale indoor triaxial tests are performed, and elastic modulus and shear strength are determined. Secondly, the macro-properties of the soil–rock mixtures with different rock contents are compared under normal and freeze–thaw states. Finally, indoor triaxial experiments are numerically simulated with Particle Flow Code software. Matched results are obtained, and the meso-mechanism of the soil–rock mixtures with different rock contents is elucidated. At the macroscale, the elastic modulus and shear strength of the soil–rock mixture decrease after the freeze–thaw cycles, and the decrement trends differ with different rock contents. At the mesoscale, the freeze–thaw cycles reduce the strength of soil–rock particles with different properties. The soil–rock mixture with 55% rock content exhibits the most severe damage among all mixtures; this mixture has the most soil–rock particle contacts because of its good compactness and skeleton structure.