Fracture mechanical properties of sandstone with pre-fabricated cracks under freeze–thaw cycles

Abstract

This paper evaluates the effect of freeze–thaw (F-T) cycles on the fracture mechanical properties of rocks with pre-fabricated cracks through experimental and numerical simulation. Three-point bending tests are conducted to determine the fracture characteristics of cyan sandstone with varying pre-fabricated crack heights. Subsequently, the failure characteristics of cyan sandstone with pre-fabricated cracks under F-T cycles are examined. A numerical model using parallel bond modeling (PBM) is established and validated against experimental results to further investigate the fracture behavior of sandstones with pre-fabricated cracks. Results demonstrate that both axial peak force and fracture toughness (KIC) linearly decrease with increasing freeze–thaw (F-T) cycles, and the axial peak force reduces with the rise in pre-fabricated crack height (Hc). The deformation damage process is categorized into four stages: compression-density, elastic deformation, pre-peak destabilization, and post-peak destabilization damage. Energy evolution is closely tied to microcrack initiation and propagation, with the majority of energy dissipating as microcrack surface energy. Both strain energy and dissipation energy decrease linearly with increased F-T cycles. These findings offer valuable insights for investigating the fracture mechanism of fractured rock mass in cold regions.