单轴压缩下岩桥长度与饱水作用对红砂岩声发射特征及破裂机制的影响

Influence of Rock Bridge Length and Water Saturation on Acoustic Emission Characteristics and Fracture Mechanism of Red Sandstone under Uniaxial Compression

摘要: 为探究岩桥长度与干燥-饱水工况对含预制双裂隙红砂岩力学特性及破裂模式的协同影响，文章设计50 mm、60 mm、70 mm岩桥长度梯度及两种水理工况，开展单轴压缩试验并同步采集声发射信号。结果表明：二者对红砂岩力学响应及细观破裂模式存在显著耦合调控效应。岩桥长度从50 mm增至70 mm时，干、饱水试样单轴抗压强度均递增，第一应力降逼近峰值应力，长岩桥可提升承载能力、延缓宏观损伤；饱水试样抗压强度与弹性模量显著低于干燥试样，水分弱化颗粒黏结并抑制微裂纹能量释放。声发射RA-AF散点图显示，岩桥长度增大使拉伸裂纹占比上升，同岩桥长度下饱水试样剪切裂纹占比更高。声发射b值可表征微破裂尺度分布，RA-AF参数精准判识破裂类型。研究成果为富水区域含裂隙岩体工程稳定性评价与灾害防控提供理论依据。

Abstract: To investigate the synergistic effects of rock bridge length and dry-saturated conditions on the mechanical properties and fracture modes of red sandstone with prefabricated double fractures, this study designed specimens with rock bridge lengths of 50 mm, 60 mm, 70 mm, and two moisture conditions, conducting uniaxial compression tests while collecting acoustic emission signals synchronously. Results show these two factors exert a significant coupled regulatory effect on the rock’s mechanical response and mesoscopic fracture modes. When the rock bridge length increases from 50 mm to 70 mm, the uniaxial compressive strength of both dry and saturated specimens rises, the first stress drop approaches the peak stress, and longer rock bridges enhance bearing capacity and delay macroscopic damage. Saturated specimens have significantly lower compressive strength and elastic modulus than dry ones, as water weakens particle bonding and inhibits microcrack energy release. Acoustic emission RA-AF scatter plots reveal that longer rock bridges increase tensile crack proportion, while saturated specimens have higher shear crack proportion than dry ones with the same rock bridge length. The acoustic emission b-value characterizes microfracture scale distribution, and RA-AF parameters accurately identify fracture types. The findings provide a theoretical basis for stability evaluation and disaster prevention of fractured rock mass engineering in water-rich areas.