Freeze-thaw effect-induced unidirectional extension of crack and rock fracture analysis

In cold regions, the water in rock fissures may freeze due to external temperature, leading to crack expansion and propagation, which induces rock damage. In this work, the rock fracture due to uniaxial expansion of tension cracks under freezing conditions was studied, and different pressures acting on the crack surfaces were analyzed from the fracture mechanics perspective. The corresponding physical model was also developed. Considering the physical and mechanical degradation, the damage to fracture toughness caused by freeze-thaw cycles was determined, and improvements were made to the existing brittle phase field finite element model (PFM). Numerical simulations and calculations were carried out at different stages throughout the entire freeze-thaw cycle to obtain the crack expansion morphological features at different stages. The results showed that hydrostatic pressure and freezing pressure are the primary loads driving the crack expansion, with freezing pressure playing a dominant role, whereas hydrostatic pressure contributes relatively little. The freezing period is the main stage of crack expansion governing the crack morphology. The thawing period accelerates the crack propagation rate, leading to rock failure. Also, the inclination angle of cracks may significantly influence rock failure. In general, rock failure results from different combinations of the initiation, expansion and connection of primary cracks under freeze-thaw action .