Investigating the Effect of Water Saturation on Rock Fracture Characteristics: Some Insights from Digital Image Correlation Technology

To investigate the fracture characteristics of rocks during the hydraulic fracturing process, Brazilian splitting experiments were conducted on cores with varying water saturations. Digital image correlation (DIC) technology was employed to capture full-field displacement and strain information during the rock fracture, facilitating the calculation of the rock fracture toughness using the path-independent J-integral. Additionally, displacement opening modes and fracture surface morphologies were obtained for rocks with different water saturations. The results show that the rock tensile strength decreases significantly as the water saturation increases. Under higher water saturations, the rock residual strength increases, showing a more obvious ductile failure mode. The fracture surfaces are found to display self-affine regimes, with a Hurst exponent β ≈ 0.62 in saturated conditions and with β ≈ 0.17 in dry conditions. Furthermore, as the integrated area of the crack tip increases, the fracture toughness gradually increases and stabilizes. The observed significant change in fracture toughness under high water saturation may be attributed to the increased plastic zone around the rock crack tip.