The deformation and failure process of coal rock under different strain rates is a significant challenge which must be solved in dynamic excavation. It is important to study the influence of strain rate on the evolution of coal rock crack. The triaxial compression tests and acoustic emission tests under the strain rate of 10⁻⁵ s⁻¹ to 10⁻³ s⁻¹ were conducted on coal rock using MTS 815 hydraulic servo-control testing machine. During the loading process, acoustic emission energy and spatial distribution have obvious stage characteristics. The damage variable is defined by acoustic emission energy, and the rate of damage evolution is obviously affected by the strain rate. Based on stage characteristics of acoustic emission energy, spatial distribution, and damage evolution, the use of damage evolution curve to determine stress threshold is proposed. In order to verify the rationality of the damage evolution method, the stress threshold values determined by damage evolution method and existing method are compared and analyzed. In order to study the effect of strain rate and confining pressure on the stress threshold, the stress thresholds under uniaxial and triaxial stress states at different strain rates were analyzed.

中文翻译：

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基于声发射的准静态应变率下深埋煤岩应力阈值研究

煤岩在不同应变率下的变形和破坏过程是一个重大的挑战，必须在动态开挖中解决。研究应变速率对煤岩裂缝演化的影响很重要。在10 ^-5  s ^-1至10 ^-3  s ^-1的应变速率下的三轴压缩测试和声发射测试使用MTS 815液压伺服控制试验机在煤岩上进行。在加载过程中，声发射能量和空间分布具有明显的阶段性特征。损伤变量由声发射能量定义，损伤演化的速度明显受应变率的影响。根据声发射能量，空间分布和损伤演化的阶段特性，提出了利用损伤演化曲线确定应力阈值的方法。为了验证损伤演化方法的合理性，对损伤演化方法和现有方法确定的应力阈值进行了比较和分析。为了研究应变率和围压对应力阈值的影响，