Failure Patterns and Morphological Soil–Rock Interface Characteristics of Frozen Soil–Rock Mixtures under Compression and Tension

Construction operations in cold regions may encounter frozen geomaterials. In construction, it is important to understand the processes by which geomaterials fail under common loading conditions to avoid accidents and work efficiently. In this work, an artificial frozen soil–rock mixture was used for uniaxial compression and indirect tension loading analysis to investigate macroscopic failure patterns and soil–rock interface crack evolution mechanisms. To further understand and compare the meso-mechanical failure mechanisms of the soil–rock interface, we used two types of rock block particles with different surface roughness for fabricating frozen artificial soil–rock mixtures. Acoustic emission (AE), ultrasonic plus velocity (UPV), and digital microscopy were utilized here to obtain the sample deformation response and analyze the morphology of the soil–rock interface. The results were as follows. From the perspective of macroscopic observation, bulging deformations and short tension cracks represent the main failure pattern under compression, and a tortuous tension crack in the center of the disk is the main failure pattern under indirect tension. From the perspective of microscopic observation, the soil–rock interface will evolve into a soil–rock contact band for the sample containing a rough rock block. The strength of the soil–rock contact band is obviously larger than that of the soil–rock interface. Three main failure patterns of the soil–rock interface were observed: a crack path through the accurate soil–rock interface, a crack path through the envelope of the rough rock block, and a crack path passing through the rough rock block. The experimental results could provide a reference for foundation engineering, especially in pile foundation engineering in cold regions.