The mechanical properties of frozen-concrete interfaces affect the stability and durability of engineering structures in cold regions. To investigate these properties, laboratory tests and numerical simulations were conducted to study the mesoscopic evolution of the shear stress-displacement relationship and the shearing process at the interface. The direct shear tests were performed at different environmental temperatures (-2 degrees C, -5 degrees C, and -10 degrees C) and normal stresses (100 kPa, 200 kPa, and 300 kPa) on the frozen soil-concrete interface, and Particle Flow Code (PFC) model of direct shear was developed. The mesoscopic parameters (particle displacement, rotation, force chain, stress, coordination number, porosity, fabric, etc.) of the interface during shearing were simulated using the PFC model. Moreover, the relationship among the interface temperature, cohesion, and friction coefficient was determined based on experimental data, and the accuracy of the PFC model was verified using previous experimental data. The results of the PFC shear model aligned well with those of the laboratory test, and the formation of shear bands was simulated well. The displacement of the soil particles on the upper layer outside the shear zone was uniform, and the direction was the same, whereas the particles inside the shear zone showed significant differences in the dislocation and rotation of the soil particles. The force chain, stress field, coordination number, and porosity were similar in the shear process and showed a concentrated distribution in the opposite direction of the shear motion, which reflected the consistency of the microcosmic response of the particles under the action of macroscopic external forces. The regression equations for the temperature, cohesion, and friction coefficient in this study can be used to simulate the shear behavior of frozen soil-concrete interfaces under different temperatures and normal stresses.

Transmedia migration of water is the key factor influencing the bond and shear mechanical properties of the interface system between soil and concrete. In numerous engineering projects, failures often occur at the soil-concrete interface, making the study of transmedia water migration in soil-concrete interface systems highly significant. This research based on the tracer properties of fluorescein to conduct a transmedia water infiltration test on silty clay-concrete interface systems. A fluorescent quantitative method was proposed to determine the moisture content within the concrete profile. The study investigated the migration of the wetting front, changes in water content, moisture distribution across the profiles of both media, and the spatial and temporal variations of soil moisture during the transmedia water migration process. The characteristics of transmedia water migration were compared under different initial soil water contents (IWC). Results demonstrated that the water distribution law of silty clay-concrete interface systems was not monotonous; notably, the water content in the interface area increased significantly. An increase in IWC inhibited the migration of the wetting front and the water content increment of the silty clay, while promoting the progression of saturation. Additionally, the water migration in the concrete was influenced by the silty clay. The proposed fluorescent quantitative method demonstrated high measurement accuracy.