Macro-Meso Fracture Mechanical Mechanisms of Creep in Brittle Rocks after High-Temperature Heat Treatment

The creep behavior of brittle rocks after high-temperature heat treatment holds significant implications for the advancement of deep subsurface resource utilization. The long-term creep mechanical responses of rocks post-heat treatment may manifest diverse tendencies amid varying confining pressures accompanying temperature escalation; However, the underlying causalities remain obscured and the research focusing on the macro-meso mechanical mechanism is scant. Based on a microcrack crack propagation model, five temperature-dependent microcrack model parameters deduced via independent experiments, including initial crack damage (D₀), fracture toughness (K_IC), crack extension stress corrosion index (n), characteristic crack propagation rate (v), and initial crack friction coefficient (μ), are introduced. A macro-meso fracture mechanics model for creep behavior of brittle rock after high-temperature heat treatment has been established. The stress-strain constitutive relationship of rock under the influence of heat treatment temperature is also obtained, which provides an important basis for the selection of stress states of creep deformation mechanism. The influences of temperatures and confining pressures on parameters such as rock initiation stress, peak strength, long-term strength, and creep failure time are studied. Empirical validation substantiates the rationale of the model. Particular emphasis is vested in delineating the impact of confining pressure on the creep fracture attributes of rocks, as temperature undergoes variations. This emphasis arises from the divergent trends characterizing the evolution of the initial crack friction coefficient with temperature fluctuation. The research findings analyze the short-term and long-term mechanical characteristics of heat-treated brittle rocks from a meso-mechanical perspective. This offers a clearer and more profound understanding of the mechanical mechanisms underlying the behavior of heat-treated brittle rocks.