高应力高渗压下裂隙岩体流变断裂微细观机理与破坏准则

In fact，the rock mass rheology is a rheologic fracture process in which the rock cracks initiate, creep, expand and cause macroscopic fractures.There are high confining pressure and high osmotic pressure in deep rock engineering, so the rheologic fracture characteristics is more obvious. According to the multi-resolution analysis theory based on macroscopy and microscopic view, used monaxial and triaxial rheological test, the scanning electron microscope(SEM) and the numerical simulation technique, adopted rheological mechanics, fracture mechanics, damage mechanics and rock hydraulics, the microcosmic mechanism and failure criterion of rheologic fracture for fractured rock mass will be studied under high stress and high osmotic pressure. Through SEM, the ageing characteristic of crack initiation , expansion and transfixion and the crack extended rule and failure mode will be made known under high stress and high osmotic pressure. Combined the theoretical analysis and rheological test results, the index system and quantification method of crack microstructure evolvement and the relationship between the microstructure change and macrographic mechanical effect will be built and the rheologic fracture criterion will be established. The rock effective damage will be equivalent to the stress and the rock rheology-damage-fracture model will be built whose internal variable are time, stress and strain, equivalent crack length and stress intensity factor. The parameters of the rheology-damage-fracture model will be identified. The research results are significant to the design, construction and stability analysis of rock engineering and can be widely used in deep rock engineering.

岩体流变实质上是一个裂纹萌生、蠕变扩展进而产生宏观断裂的流变断裂过程。深部岩体工程高地应力、高渗透压的特殊赋存环境，使得岩体的流变断裂特性更加显著。基于微细观、宏观的多尺度理论，利用单轴、三轴流变试验与数值模拟技术等手段，采用流变力学、断裂与损伤力学等理论研究高应力、高渗压下裂隙岩体流变断裂微细观机理与破坏准则。通过岩石流变试验，研究岩石裂纹萌生、扩展到贯通破坏的演化累积时效特征和裂纹扩展规律与破坏模式；结合理论分析与流变试验结果，建立蠕变裂纹微细观结构演化的表征指标、量化方法以及与宏观力学效应之间的量化关系，并构建流变断裂准则；从损伤力学角度建立以时间、应力应变、裂纹等效长度与类应力强度因子为参变量的多裂纹相互影响的岩石流变-损伤-断裂模型，并对模型进行参数识别。研究成果可广泛应用于深部岩体工程，对岩体工程设计与施工、失稳预测及稳定性分析具有重要意义。

深部岩体工程特殊的赋存环境，使其流变断裂特性更加显著。裂隙岩体在流变过程中裂纹起裂、扩展及贯通模式以及含贯通裂纹岩体的流变破坏特征是值得深入研究的难点问题。本项目通过试验，理论分析对含贯穿裂纹砂岩的流变断裂机制进行研究，主要取得了如下几个方面的结论与创新性研究成果：进行了完整岩石试件，含一条贯通裂纹岩石试件、含两条贯通裂纹岩石试件的瞬时破坏试验和蠕变破坏试验；根据分级加卸载曲线及应力-应变曲线可知，试件在各级荷载作用的瞬时轴向应变与轴向荷载大小成比例增长，在各分级荷载下，蠕应变增加量与瞬时轴向应变的比率呈现提高趋势，且试样的瞬弹性应变与瞬塑性应变均随应力的增高而增大，但瞬塑性应变增加幅度较瞬弹性应变大，这说明该岩样材料抵抗瞬塑性变形的能力随应力的循环增加而增强。通过分析，发现含贯通裂纹的岩石试件在蠕变过程中具有黏、弹、塑三性共存的特点，并且在第7级加载下呈现出明显的非线性加速蠕变现象。由此，考虑蠕变参数的损伤，建立变参数流变损伤模型，并得到本构方程和蠕变方程，对模型参数进行了识别。对比瞬时破坏和蠕变破坏两种加载模式下裂纹的起裂、扩展至贯通破坏的异同，考虑岩体中裂纹的相互作用对裂纹尖端应力场的影响，引入蠕变断裂应力强度因子，提出了流变断裂破坏准则。课题研究结果有一定的创新性，可为探讨复杂环境中裂隙岩体的流变断裂破坏提供思路与手段。