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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.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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