The propagation and interaction of cracks under freeze-thaw cycling in rock-like material

In cold mountainous regions, the freeze-thaw cycling often leads to rock weathering, which might trigger spalling, significant landslides and rockfalls. In this work, we used combined experimental, theoretical and numerical approaches to investigate the mechanisms of frost cracking as a result of coupled effects of freeze-thaw cycling, confining stress and the interaction of multiple cracks. The experimental facility with a temperature cycling chamber and a high-pressure cell has been developed. We used rock-like materials (rock analogue samples made from cured cement and quartz-sand mixtures) to conduct the experiments. The rock-like samples contain pre-existing single or double initial cracks, which are then water filled and exposed to freeze-thaw cycling. The coupled thermal-hydro-mechanical modeling for analyzing fractures induced by freeze-thaw cycling was achieved by using a code that was previously developed named TOUGH-AiFrac. Good agreements between the TOUGH-AiFrac modeling and the laboratory experiments have been achieved including the exact paths of crack propagation. The experimental and numerical results show that the frost cracks tend to propagate in the direction of maximum principal stress. The results further show that the interaction effect between two frost cracks is significantly influenced by the position, orientation and offset of initial cracks, as well as the orientation of intact rock bridges between the cracks. At last, the stress shadow that was calculated by the TOUGH-AiFrac model between two cracks was discussed.