Subcritical crack growth in granite based on dissolution kinetics

Subcritical crack growth (SCG) in fluid-rock interactions plays a crucial role in understanding crustal deformation and fracture network development. Using a double-torsion technique, the subcritical crack growth and fracture characteristics of Zhangzhou granite were investigated under fluids with different pH values. Subcritical crack growth index (SCI) was reduced in both acidic and alkaline fluids compared with the neutral environment, with reduction percentages of 9.8% to 31.9% under acidic environment (pH = 1-5) and 8.3%-17.5% under alkaline environment (pH = 10-14), respectively. In contrast, the weakening effect of fluid pH values on critical stress intensity was less than that of SCI. Scanning electron microscopy (SEM) results showed that grain boundaries were prone to dissolution compared to the basal surface, proving that subcritical cracks preferentially propagate along the grain boundaries. Fracture toughness was insensitive to fluid pH values in the short term but sensitive to solution salinity. Considering mineral compositions and contents, a rock dissolution rate was defined, and a SCI prediction model was proposed, which was demonstrated to be capable of estimating variations in SCI under various fluid environments for different rock types and could provide valuable insights for engineering applications and environmental assessments. • Subcritical fracture experiments have been conducted on granite under fluid conditions with a wide range of pH values (1-14). • Subcritical crack growth index and critical stress intensity exhibit similar pH-dependent characteristics. • A predication model for subcritical crack growth index as a function of dissolution rate is proposed.