基于晶体塑性理论的岩盐蠕变渐进破坏本构模型研究

As one of the main media for national underground strategic storages, the long-term mechanical behavior of rock salt has been the important research content for those safety and stability assessment. In order to evaluate and predict the effect of rheological properties of rock salt objectively and accurately, this project focuses on micromechanics constitutive model and the multi-scale numerical simulation of rock salt, which are based on its microscopic deformation mechanisms and damage characteristics. First of all, according to the microscopic observation and macroscopic mechanical tests, not only the microscopic mechanism of deformation and damage characteristics are studied, but also the relationship between macro- and micro-mechanical parameters of rock salt is established. Secondly, based on the deformation mechanisms obtained (especially the crystal dislocation glide, the grain boundary damage and fracture, as well as the evolution of microcracks) and utilizing the homogenization theory, a micromechanics constitutive model taking into account the interaction of multi-mechanism is proposed. Finally, efficient parallel computing program is developed under the framework of finite deformation theory and verified by experiment data. The developed micromechanics constitutive model is capable for structural scale calculation when combining with the finite element code as long as the evolution of microscopic structure and stress-strain relation at critical failure point under different loading conditions are provided. This research not only enriches the aging-associated micromechanics theory and numerical model of rock salt, but also provides a new approach for evaluating the long-term safety and stability of storages.

作为国家地下战略储库的常用介质，岩盐的长期力学行为是储库安全稳定性评估的重要研究内容。为了客观、准确地评估并预测岩盐流变特性，本项目重点研究基于岩盐细观变形机制和损伤特征的细观本构模型和多尺度数值模拟方法。首先，通过显微观测和宏观力学试验，研究岩盐细观变形机制和损伤特征，并建立岩盐宏细观参数之间的数学映射关系。其次，基于细观变形机制（重点考虑晶体位错滑移、晶界损伤断裂以及微裂纹演化），借助于均匀化理论，建立可考虑多变形机制相互作用的细观损伤本构模型。最后，在有限变形框架下，研发高效并行计算程序，结合试验结果对模型进行验证。利用模型预测不同加载路径条件下细观结构的演化和临界破坏点的应力-应变关系，结合有限元开展结构计算。该项研究成果将丰富岩盐与时效相关的细观理论和数值模型，为储库长期安全稳定性评估提供新的分析方法。

作为国家地下战略储库的常用介质，岩盐的长期力学行为是储库安全稳定性评估的重要研究内容。目前大部分学者认为，将岩盐作为多晶体材料研究，有助于明确岩盐宏观变形特性的细观机理。基于此，开展了如下工作：1）基于改进的连续应变偏差法（refined continuous strain deviation）对实验数据进行了分析，提出了一种定量确定弹性参数E和v的方法，该方法可为细观参数的确定提供更可靠的宏观力学参数；2）构建了考虑接触面效应的Eshelby求解框架。假定界面满足简化的弹簧模型（应力连续，位移不连续），推导了含界面效应的Eshelby张量。系统研究含界面效应时，相关细观力学参数对材料宏观力学性能的影响；3）构建孔隙和夹杂变形耦合的细观损伤本构模型并将其程序化。从细观角度推导了含孔隙率影响的屈服面方程，提出了具有明确数学和物理意义的塑性乘子表达式并提出了相应的数值积分算法。将该算法和之前推导的含界面效应的Eshelby张量结合，研究了加载的率相关效应和长期力学行为；4）开展基于Voronoi单元的晶体塑性-损伤耦合全场模拟和非均质地层水力压裂初步研究两项预研。第一项预可研有助于更深刻的了解晶体的细观变形特征及其对宏观性能的影响。第二项预研基于非均质夹杂地层研究了夹杂对单裂纹和平行双裂缝扩展模式的影响，相应的预可研成果能为未来开展盐类矿床水压致裂和水溶开采等研究提供指导。