Experimental Study on Uniaxial Compressive Fatigue Property of Cracked Rock-like Materials
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摘要: 为了研究含穿透裂隙类岩石的疲劳破坏行为，揭示含缺陷岩石疲劳损伤和破坏机理，本研究采用预埋抽条法制作含穿透裂隙白水泥试样，通过单轴压缩疲劳试验，探讨不同的裂纹倾角和应力分布对裂纹扩展的影响。试验结果表明：（1）低周疲劳破坏形态与静载压缩破坏形态基本一致，裂纹都是从裂隙尖端萌生，起裂角约为45°～75°，呈一定弧度向受压两端扩展，直至试样破坏，为典型的张拉I型断裂；（2）建立裂纹扩展长度与循环次数关系后发现，裂纹扩展速率随着循环次数的增加而先迅速增加后趋于平稳，最后又迅速增加，验证了疲劳破坏过程经历三个阶段，即疲劳裂纹初始塑性形变阶段、裂纹的缓慢增长阶段和裂纹的快速贯通阶段；（3） 根据对疲劳应变能的分析可以看出，裂纹在萌生阶段所需要的能量较大，在裂纹开始扩展后，应变能密度基本保持不变，说明裂纹扩展过程中所需要的能量趋于稳定；通过对比不同应力水平、应力比的应变能密度曲线可以看出，在较大的应力水平、应力比下，应变能密度逐渐增加，表明试样在较大的应力水平和应力比下能够吸收更多的能量，裂纹的萌生与扩展也就更快。Abstract: To study the fatigue failure behavior of rocks with penetration cracks and reveal the fatigue damage and failure mechanism of rocks with defects, the cracked white cement specimens were prepared by pre-embedded strip method. The effects of various crack inclination angles and stress distribution on crack propagation was revealed by uniaxial compression fatigue test. The result showed that the fracture trajectory of the low cycle fatigue test was basically the same as that of the static test. The crack initiated from the crack tip and the crack angle was about 45°~75°, which could be considered as typical tensile Mode I fracture. The relationship between crack propagation length and the number of cycles revealed that the crack growth rate increased rapidly with the number of cycles and then underwent a stable phase and finally increased rapidly, which has been verified that the fatigue failure process went through three stages: initial plastic deformation stage, slow growth stage and rapid infiltration stage. According to the analysis of fatigue strain energy, energy required by the crack in the initiation stage was relatively large, and after the crack started to expand, the strain energy density remained basically unchanged, indicating that the energy required in the process of crack expansion tended to be stable. Comparing the strain energy density curves of different stress levels and stress ratios, the strain energy density gradually increased at larger stress levels and stress ratios, indicating that the sample could absorb more energy under larger stress levels and stress ratios, and the energy of crack initiation and propagation was faster.
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Key words:
- crack propagation /
- fatigue /
- strain energy density /
- failure mechanism /
- rock-like materials
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表 1 试样参数
倾角 编号 应力振幅SD/MPa 应力水平Smax/Sc 应力比Smin/Smax 30° T1 3 0.36 0.250 T2 4 0.54 0.333 T3 5 0.54 0.167 T4 5 0.63 0.286 T5 5 0.72 0.375 T6 6 0.72 0.250 45° F1 5 0.48 0.167 F2 5 0.56 0.286 F3 5 0.60 0.333 F4 5 0.64 0.375 60° S1 5 0.61 0.286 S2 5 0.65 0.333 S3 5 0.69 0.375 S4 6 0.69 0.250 
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