为揭示应变率对岩石宏观破坏特征及微观裂纹扩展规律的影响，以砂岩为研究对象，开展了不同加载速率条件下的单轴压缩试验与声发射信息实时监测，分析了加载速率对砂岩试样强度和变形特性、破坏模式、破碎特征等宏观力学响应及微观断口形貌的影响，并基于声发射b值随加载过程的演化，探讨了不同加载速率条件下的砂岩试样内部裂纹扩展规律。研究结果表明：在1 × 10^-5 ~ 1 × 10^-2 s^-1的加载速率范围内，砂岩试样的单轴抗压强度、弹性模量与加载速率呈正相关关系，加载速率每增大10倍，单轴抗压强度与弹性模量分别增大2.66 MPa和0.087 GPa，而峰值应变减小0.213‰；随加载速率增大，破坏特征呈现从单一倾斜的贯穿断裂面，逐渐向多断裂面交叉分布形式转变的趋势，且碎块平均尺寸减小，表明砂岩试样的破坏程度增大；低加载速率下的微观断口形貌以沿晶裂纹为主，而随加载速率增大，穿晶裂纹与沿晶裂纹交替出现，且裂纹相交位置破碎特征明显，出现晶粒的大面积剥离；随加载速率增大，声发射b值从增大变减小的转折点所对应的应力与峰值应力的比值降低，表明加载速率越大，试样内部越易出现裂纹的扩展，并贯通形成较为明显的大裂纹，导致试样呈现出更为严重的破坏特征和复杂的裂纹扩展规律。研究结果对认识复杂应力条件下工程围岩的破坏特征，以及基于声发射监测信息预测围岩内部结构的损伤劣化规律具有重要指导意义。

In order to reveal the influence of strain rates on the macroscopic failure characteristics and microscopic crack propagation laws of rock, sandstone was taken as the research object, and the uniaxial compression tests and real-time monitoring of acoustic emission information were carried out under different loading rates. The influence of loading rates on the macroscopic mechanical response and microscopic fracture morphology of sandstone specimens, such as strength and deformation characteristics, failure mode and fracture characteristics, was analyzed. Based on the evolution of acoustic emission b value with the loading process, the internal crack propagation laws of sandstone specimens under different loading rates were explored. The research results show that within the loading rate range of 1 × 10^-5 ~ 1 × 10^-2 s^-1, the uniaxial compressive strength and elastic modulus of sandstone samples were positively correlated with loading rates. For every 10 times increase in loading rate, the uniaxial compressive strength and elastic modulus increased by 2.66 MPa and 0.087 GPa, respectively, while the peak strain decreases by 0.213‰. As the loading rate increased, the failure characteristics showed a trend of gradually transitioning from a single inclined through fracture surface to a cross distribution of multiple fracture surfaces, and the average size of the fragments decreased, indicating an increase in the failure of the sandstone sample. At low loading rates, the microstructure of the fracture surface was mainly characterized by intergranular cracks, while as the loading rate increased, transgranular cracks and intergranular cracks alternated, and the fracture characteristics at the intersection of the cracks were obvious, resulting in large-scale grain peeling. As the loading rate increased, the ratio of stress to peak stress corresponding to the turning point where the acoustic emission b value changes from increasing to decreasing decreased. This indicated that the higher the loading rate, the more likely cracks were to propagate inside the specimen and form more obvious large cracks, leading to more severe damage characteristics and complex crack propagation patterns in the specimen. The research results have important guiding significance for understanding the failure characteristics of engineering surrounding rock under complex stress conditions, as well as predicting the damage deterioration law of the internal structure of surrounding rock based on acoustic emission monitoring information.