节理岩体裂纹扩展及失效演化宏细观机理研究

Flaws distribute randomly in natural rocks mass，When a brittle rock is under complex loading, these defects would nucleate, propagate and coalesce from the pre-existing inhomogeneities, which would eventually effect the damage evolution and failure behavior of rocks mass. This project employs the self-developed DIC(Digital Image Correlation) macro and microscopic visualization analysis system, which can actualize the whole process and refinement measurement, and the means of SEM(scanning electron microscope) and numerical simulation into the investigation on the macro and microscopic mechanism of the cracks propagation and the failure evolution of the jointed rock masses with the combination of macro and microscopic methods. Through visual the macro and microscopic test under complex loading and SEM test, the macro and microscopic constitutive model is established with the consideration of microscopic damage. And the numerical simulation would be applied to disclose the inner link between microscopic mechanical mechanism and macroscopic mechanical response.Combining the experimental and numerical studies, the discrete and continuous hybrid numerical method would be established with consideration of the macro and microscopic parameters of jointed rock masses. And the further simulation testes would be implemented to reveal the macro and microscopic mechanism and damage evolutionary rules in the failure process of the jointed rock masses.（3）Through visual centrifuge test and numerical simulation, based on the measured data, the microscopic model would be verified, as well as revealing the damage and failure mechanism of the jointed rock slope under the condition closing to the actual stress field. This research would be conducive to reveal macro and microscopic mechanical mechanism in the damage and failure process of the jointed rock masses, which provides a thoroughly understanding to the disaster mechanism of jointed rock mass engineering.

天然岩石内部存在大量的微裂隙等缺陷。在外荷载作用下，随机分布的缺陷会不断聚合、扩展、贯通，并最终影响岩石的损伤演化及破坏形态。本项目拟采用自主研发的具有全过程、精细化量测功能的DIC可视化宏细观分析系统，结合SEM扫描以及数值模拟等手段，从细观层面入手、宏细观结合方法研究节理岩体裂纹扩展及失效演化宏细观机理：(1)通过可视化复杂荷载加载宏细观试验及SEM电镜扫描试验，建立考虑细观损伤的宏细观本构模型，结合数值模拟揭示细观力学机理与宏观力学响应之间内在联系；(2)通过室内试验及数值方法研究，建立考虑宏细观参数的节理岩体离散-连续混合数值方法，通过数值试验，揭示节理岩体破坏的宏细观力学机理和失效演化规律；(3)结合工程实际，通过可视离心试验，验证细观模型，揭示接近实际应力场条件下节理岩体边坡失效破坏机理。本研究将有助于揭示节理岩体破坏失效的宏细观力学机理，提升人们对节理岩体工程灾变机理的认识。

课题完成了采用自主开发的数字图像分析软件的含预置单裂纹、双裂纹岩体在单轴压缩下的应变场的扩展演化规律。对含不同预制裂隙岩体进行了不同围压下的常规三轴试验，系统地了解了裂隙倾角和围压对岩样的强度特征和变形规律。采用扫描电子显微镜将岩石断裂面细观形貌特征与裂纹生核、起裂、扩展及岩石整体破坏演进方式及过程中不同力学作用性质的分布规律建立联系，并结合相关量化分析方法，对岩石损伤机制进行探讨。通过对裂纹尖端应力、应变场理论模型基于自定义参量的分析，并与试验主应变场进行比较，最终建立了基于应变的强度准则。将该准则应用到扩展离散元数值模拟中，并将模拟结果与室内试验结果比较，以进一步揭示岩体裂纹萌生、扩展、贯通的规律与机理。对含不同裂纹倾角的单裂纹花岗岩试样进行单轴压缩试验。通过数字图像相关技术深度分析了单轴试验下的新生宏观裂纹起裂以及扩展过程的全局拉伸、剪切应变场演化情况。.综上，本研究系统研究了岩石材料受荷过程中宏观力学表现，利用电镜扫描技术分析了拉剪裂纹细观力学特性，基于断裂力学裂纹扩展理论，展开了对裂纹尖端应力场和应变场的对比研究，针对断裂力学中经典断裂准则：格里菲斯准则与摩尔-库伦准则进行改进，提出了基于全局应变场的应变强度准则。该准则能够同时兼顾拉伸、剪切裂纹的判别，并大幅提升拉伸裂纹的判别精度。同时得到了岩石裂纹起裂、扩展、贯通过程中的全局应变场及岩石变形破坏过程不同阶段的具体特征，在材料脆性破坏瞬态演化过程的记录与量化分析方面做出了突出贡献，构建了了裂纹贯通过程中宏观力学机制与细观断裂机理的联系。通过揭示岩体破裂过程中宏观力学响应及细观特性的影响，提出了基于全局应变场的应变强度准则及相应扩展离散元数值计算方法的灾变分析方法，为耦合应力条件下岩体工程破坏的预测提供了理论依据，对于探究岩体工程的失效机理具有重要学术价值，对提高岩体的设计水平等具有重要的科学意义和工程实际意义。