Abstract To explore the variation in rock acoustic emission (AE) characteristics with strain rate, uniaxial compression tests at different loading rates and impact loading tests were conducted on granite using a MTS322 rock mechanical test system and split Hopkinson pressure bar (SHPB) system, respectively. The effect of the strain rate on the AE characteristic parameters, rock fracture properties, and destruction evolution were systematically analyzed. The results demonstrated that with increasing strain rate, the cumulative AE count decreases as a power function, and the variation between the cumulative AE count and strain rate can be fitted log-linearly with a slope of 0.48. The peak frequencies of the AE signals are mostly distributed in the zones of 0–100 kHz, 175–250 kHz, and 400–550 kHz. The signal proportion in the 0–100 kHz zone gradually increases with strain rate, while the signal proportions in the 175–250 kHz and 400–550 kHz zone exhibit decreasing trends. A transition of a sudden increase in the RA-value and decrease in the AF-value occurs when the stress reaches a certain level, and the stress level corresponding to this transition will increase with strain rate. Meanwhile, the RA–AF distribution is mostly concentrated on the abscissa in the low strain rate tests, but gradually concentrates on the longitudinal axis as the strain rate increases. This indicates that tensile cracking becomes the dominant fracture mode with increasing strain rate. The b-value decreases with increasing strain rate in the uniaxial compression tests; however, the b-value in the impact loading tests is higher than that in the uniaxial compression tests. Furthermore, to distinguish the signals generated by stress wave propagation from the signals generated by rock fracturing in the impact loading tests, a four-parameter k-means algorithm is used to conduct a clustering analysis. The results indicate that the signals can be classified into four clusters: tensile fracturing signals (cluster A), mixed stress wave and shear fracture signals (cluster B), mixed stress wave and tensile fracture signals (cluster C), and stress wave signals (cluster D).

中文翻译：

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应变速率对岩石声发射特性影响的试验研究

摘要 为了探究岩石声发射(AE)特性随应变率的变化，分别采用MTS322岩石力学试验系统和分体式霍普金森压力棒(SHPB)系统对花岗岩进行了不同加载率下的单轴压缩试验和冲击加载试验。 . 系统分析了应变速率对声发射特征参数、岩石断裂特性和破坏演化的影响。结果表明，随着应变率的增加，累积 AE 计数作为幂函数减少，并且累积 AE 计数和应变率之间的变化可以以 0.48 的斜率对数线性拟合。AE 信号的峰值频率主要分布在 0-100 kHz、175-250 kHz 和 400-550 kHz 区域。0-100 kHz 区域的信号比例随着应变速率逐渐增加，而 175-250 kHz 和 400-550 kHz 区域的信号比例呈下降趋势。当应力达到一定水平时，会出现 RA 值突然增加和 AF 值减小的转变，并且与这种转变对应的应力水平会随着应变率的增加而增加。同时，在低应变率试验中，RA-AF 分布主要集中在横坐标上，但随着应变率的增加逐渐集中在纵轴上。这表明随着应变速率的增加，拉伸开裂成为主要的断裂模式。在单轴压缩试验中，b 值随着应变速率的增加而减小；然而，冲击载荷试验的 b 值高于单轴压缩试验的 b 值。此外，为了在冲击载荷试验中区分应力波传播产生的信号和岩石破裂产生的信号，采用四参数k-means算法进行聚类分析。结果表明，信号可分为四个簇：拉伸断裂信号（簇A）、混合应力波和剪切断裂信号（簇B）、混合应力波和拉伸断裂信号（簇C）和应力波信号（集群 D)。