Elastoplastic Crack Initiation Behavior of Unsaturated Rock Fractures (Cavities) With Asymmetric Hole-Edge Cracks Under Gas-Ice Pressure

Abstract

Current research on frost heave-induced cracking in fractures of rock masses in cold regions typically assumes that fractures are fully saturated. However, in actual engineering practice, rock mass fractures are often in an unsaturated state. Upon freezing, the fracture surfaces are subjected to a complex combination of gas pressure, freezing pressure, and ice friction forces. This study investigates the crack initiation mechanisms of unsaturated rock fractures with asymmetric edge cracks under gas-ice pressure conditions. Assuming a small yield range, we derive the calculation formulas for gas pressure after freezing, stress intensity factor, crack initiation angle, and crack initiation stress based on the complex variable function and elastic-plastic crack mechanics theory. Additionally, an improved phase-field model is proposed for calculating dynamic crack propagation in mixed-mode I-II fractures, with key parameters analyzed and discussed. The results demonstrate that: By comparing the analytical solutions with numerical calculations, the validity of the proposed model is verified. During the freezing process, dynamic crack propagation in unsaturated fractures will exhibit bifurcation. At higher water saturation levels, crack propagation shows a pattern of initial bifurcation followed by subsequent merging.