Characteristics of Shear Creep Fracture in Deep Hard Rock Induced by Initial Disturbance and the Regularities of Acoustic Emission Precursors
摘要
The influence of deep mining initial disturbance on the shear creep deformation of surrounding rock in shafts and chambers is highly sensitive. Analyzing the mechanical properties and precursor characteristics of shear creep failure of deep hard rock after being subjected to localized impact disturbance is of great significance. Using a self-developed rock localized impact disturbance test apparatus, shear creep tests were conducted on gneiss samples under varying conditions of axial stress, disturbance frequency, and impact area. Acoustic emission technology was applied to analyze the temporal evolution of rock shear failure, crack propagation patterns, and precursor responses. At the same time, SEM was used to conduct a microscopic analysis of the shear failure surface. Results indicate that initial localized impact disturbances accelerate rock failure, with the degree of influence on the total shear creep failure duration and shear strength following the order: axial stress > impact area > disturbance frequency. The mesoscopic characteristics of the shear fracture surface are diverse, such as sheet-like twisted fractures, stepped fractures, river patterns, and traces of mineral particles. The AE energy parameters closely align with the creep curve, and the correlation is best described by an exponential function. Higher axial stress usually inhibits tensile crack formation. Compared to undisturbed specimens, the proportion of tensile cracks in specimens subjected to localized impact disturbance increases by 3.9–11.8%. The initial disturbance also influences precursor signals, including the AE quiet period preceding shear fracture failure (accounting for 2.9–3.9% of the total time before shear creep failure), accelerated energy release, sharp increases in cumulative energy curves, the coexistence of low-frequency, high-amplitude signals and multi-frequency bands, as well as a continuous decrease in the AE b value followed by a rapid drop in