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预制裂隙对坚硬砂岩力学特征的弱化效应试验研究

Research on the weakening effect on mechanical characteristics of hard sandstone with prefabricated crack

  • 摘要: 为研究预制裂隙对坚硬岩石力学特性和破坏特征的影响规律,采用实验室实验和数值模拟相结合的方法,对不同裂隙长度、角度的坚硬砂岩试样开展单轴压缩试验。从应力—应变、裂隙扩展形态及数量演化、声发射特征等角度分析,揭示了预制裂隙对坚硬岩石的弱化效应。研究结果表明:不同裂隙形态对坚硬砂岩强度弱化程度不同,随着裂隙角度的增大力学强度先降低后升高,随着裂隙长度的增加力学强度逐渐降低,裂隙长度越长或角度越接近45°,更易发生剪切破坏;裂隙尖端易形成应力集中,并衍生出翼裂隙和次生裂隙,从而改变完整岩石的劈裂破坏模式,降低了岩石瞬间破坏的剧烈程度;在裂隙对坚硬岩石弱化规律方面,数值模拟结果与实验室实验结果具有良好一致性,基于损伤变量计算公式,定量分析了预制裂隙对坚硬岩石强度的弱化改性效应。

     

    Abstract: This study explores how prefabricated crack affect the mechanical properties and failure characteristics of hard rock. We conducted both laboratory experiments and numerical simulations to perform uniaxial compression tests on hard sandstone samples with varying fracture lengths and angles. By examining stress-strain relationships,fracture propagation,and acoustic emission characteristics,we found that prefabricated crack weaken hard rock in specific ways. The results show that different fracture morphologies lead to varying degrees of strength weakening in hard sandstone. Specifically,mechanical strength initially decreases and then increases as the fracture angle increases,while it consistently decreases with longer fracture lengths. Longer fractures or those angled closer to 45° are more likely to result in shear failure. Stress tends to concentrate at the fracture tips,causing the formation of wing and secondary fractures,which changes the splitting failure mode of intact rock and lessens the severity of sudden rock failure. The numerical simulations align with the laboratory findings on the weakening patterns caused by fractures. Using a damage variable calculation formula,we performed a quantitative analysis of the weakening and modification effects of prefabricated crack on hard rock strength.

     

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