This study is aimed at revealing the effect of dynamic loading frequency on the fracture evolution behavior in preflawed rock samples under multistage cyclic loading conditions. The fracture evolution characteristics were investigated using stress-strain descriptions and in situ acoustic emission techniques. It is shown that rock strength, deformation, AE pattern, and fatigue life are strongly affected by the applied dynamic loading frequency. Rock fatigue strength and lifetime increase with the increase of dynamic loading frequency. The AE count and energy output both increase with the increase of the applied loading frequency. Six kinds of cracking modes were revealed by AE spectral frequency analysis. It is shown that large-scaled cracks are easy to be formed for rock subjected to high-frequency loads, reflected as the deceasing of AE signals with high-frequency–high-amplitude signal feature. It is suggested that applied dynamic loading frequency has obvious impact on the crack coalescence at the rock bridge segment. The testing results are helpful to enhance the cognitive of the influence of dynamic frequency on the crack communication behavior and can be expected to predict the stability of rock mass structures where rock mass is subjected to fatigue loading.

中文翻译：

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多级循环荷载作用下动态频率对预裂岩裂缝演化影响的研究：声发射监测的洞察

本研究旨在揭示动态加载频率对多级循环加载条件下预裂岩样裂缝演化行为的影响。使用应力-应变描述和原位声发射技术研究了裂缝演化特征。结果表明，施加的动态加载频率对岩石强度、变形、AE 模式和疲劳寿命有很大影响。岩石疲劳强度和寿命随着动态加载频率的增加而增加。AE 计数和能量输出都随着应用加载频率的增加而增加。AE谱频率分析揭示了六种裂纹模式。结果表明，岩石在高频载荷作用下容易形成大面积裂缝，反映为具有高频高幅度信号特征的 AE 信号的衰减。表明施加的动力加载频率对岩石桥段裂缝合并有明显影响。测试结果有助于增强对动力频率对裂缝沟通行为影响的认知，可望预测岩体受疲劳荷载作用下岩体结构的稳定性。