脆性岩石渐进及蠕变失效特性宏细观力学模型研究
Macro-micro mechanical model for progressive and creep failure of brittle rock
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摘要: 压应力作用脆性岩石渐进及蠕变失效特性是其力学性质研究的两个主要研究方向。其对于深部地下开挖围岩稳定性的判断有着重要的指导意义。岩石内部微裂纹扩展对脆性岩石的渐进及蠕变特性有着重要的影响。因此,基于岩石的应力与裂纹扩展关系及裂纹扩张演化法则,并结合宏细观损伤定义之间的关系,提出了一个新的宏细观力学模型,推出了岩石完整的应力-应变关系与蠕变理论表达式。分析了围压对岩石的应力-应变关系的影响。研究了岩石内部初始微裂纹尺寸及裂纹间摩擦系数对应力应变关系及岩石强度的影响。并给出了不同围压下岩石裂纹初始应力与峰值应力,其对蠕变实验中的施加应力初始值选取提供了一定参考。然后,研究了恒定围压、轴压分级加载应力路径下的岩石蠕变应变及应变率变化趋势。通过试验结果验证了理论模型的合理性。进而,对压应力作用下细观裂纹扩展对岩石力学特性影响的理解提供了一定的理论参考。Abstract: The progressive and creep failure of brittle rock in compression plays an important role in the investigation of rock mechanics. It has great significance for judging the stability of surrounding rock in deep underground. Furthermore, growth of microcracks of brittle rock has great influence on creep properties. Based on the relation between stress and crack growth, and on the evolution law of crack growth, and considering the link of damage in micromechanical and macroscopic scales, a new macro-micro model is proposed. The theoretical expressions for stress-strain relationship and creep are derived. The effects of confining pressure on the relationship between stress and strain are analyzed. The effects of initial mcirocrack size and friction coefficient on stress-strain relationship and rock strength are also investigated. The crack initiation stress and the peak stress under different confining pressures are obtained, which provides a reference for applied stress under creep tests. The creep strain and strain rate under constant confining pressure and step axial loading are analyzed. Rationality of theoretical results is verified by these experimental results. It may provide the theoretical reference for understanding the effects of microcrack growth on the mechanical properties of brittle rock in compression.