苗胜军, 尚向凡, 王辉, 梁明纯, 杨鹏锦. 近疲劳强度循环荷载下粉砂岩强度变化机制研究[J]. 工程科学学报. DOI: 10.13374/j.issn2095-9389.2023.07.31.003
引用本文: 苗胜军, 尚向凡, 王辉, 梁明纯, 杨鹏锦. 近疲劳强度循环荷载下粉砂岩强度变化机制研究[J]. 工程科学学报. DOI: 10.13374/j.issn2095-9389.2023.07.31.003
Strength change mechanism of siltstone under near fatigue strength cyclic loading[J]. Chinese Journal of Engineering. DOI: 10.13374/j.issn2095-9389.2023.07.31.003
Citation: Strength change mechanism of siltstone under near fatigue strength cyclic loading[J]. Chinese Journal of Engineering. DOI: 10.13374/j.issn2095-9389.2023.07.31.003

近疲劳强度循环荷载下粉砂岩强度变化机制研究

Strength change mechanism of siltstone under near fatigue strength cyclic loading

  • 摘要: 通过开展不同循环次数的循环加卸载试验,结合声发射和CT扫描技术,揭示了近疲劳强度循环荷载作用下泥质石英粉砂岩的细观破裂演化规律、裂隙扩展特征与强度变化机制。结果表明:(1)泥质石英粉砂岩的损伤应力小于疲劳强度,可称损伤应力与疲劳强度之间的应力水平为近疲劳强度。(2)近疲劳强度循环荷载对粉砂岩有明显的劣化或强化作用,随着循环次数增加,岩石峰值强度先小幅下降后持续增加最终趋于稳定。(3)循环加卸载改变了泥质石英粉砂岩的破裂模式,岩石由单轴压缩时的张拉破坏转变为低次数循环加卸载转单调加载的剪切破坏,并随着循环次数的增加过渡为张拉-剪切共轭破坏。(4)当循环次数较低时,循环加卸载过程中粉砂岩的弱胶结结构断裂,微裂纹进一步扩展,转单调加载后岩石破裂尺度增大、内部裂纹局部集中,发生劣化。(5)当循环次数较高时,循环加卸载过程中粉砂岩颗粒破碎并重新排布,密实度增加,有效承载面积增大,转单调加载后岩石裂隙尺寸、裂隙密度和破碎程度降低,发生强化。

     

    Abstract: Through the cyclic loading unloading to monotonic loading test, combined with acoustic emission and CT scanning technology, the micro fracture evolution law, fracture structure characteristics and strength change mechanism of argil-laceous quartz siltstone under near fatigue strength cyclic loading are revealed. The results show that: (1) the damage stress of argillaceous quartz siltstone is less than the fatigue strength, so the stress level between the damage stress and the fatigue strength can be called as near fatigue strength. (2) The near fatigue strength cyclic load has obvious deterioration or strengthening effect on siltstone, the peak strength of rock decreases slightly with the increase of the number of cycles, then increases continuously and finally tends to be stable. (3) Cyclic loading and unloading changed the fracture mode of argillaceous quartz siltstone, the rock changed from tensile failure under uniaxial compression to shear failure under low cyclic loading and unloading to monotonic loading, and with the increase of the number of cycles, it transited to tensile shear conjugate failure. (4) When the number of cycles is low, the weak cementation structure of siltstone breaks during cyclic loading and unloading, and the microcracks further expand, after monotonic loading, the rock fracture scale in-creases, and the internal cracks concentrate locally, leading to deterioration. (5) When the number of cycles is high, siltstone particles are broken and rearranged during cyclic loading and unloading, the compactness increases, the effective bearing area increases, and the rock fracture size, fracture density and fragmentation degree decrease after monotonic loading, resulting in strengthening.

     

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