Collaborative Research: Salt Rock Microstructure and Deformation

盐岩被用来安全地储存石油、高压气体和核废料，因为它能够蠕动并形成气体和液体流动的障碍。然而，地下存储设施附近的蠕变过程可能会导致裂纹脱粘、打开、关闭和重新粘结，从而危及流动屏障的完整性和工程结构的稳定性。关于裂纹和愈合的数学描述还不够完善。该奖项将支持基础岩石物理和力学研究，将裂缝剥离、张开和重新结合到微观结构和力学变量的变形联系起来，这些变量控制着盐岩在地质空间和时间尺度上的时间相关行为。盐的变形在实验室条件下发生得很快，这使它成为研究其他晶体材料和多孔介质中损伤和愈合的很好的模拟。项目发现有望推进量化关系，从而能够对工程项目中的行为进行准确的建模和预测。这项工作将促进对其他岩石破裂和愈合的基本理解，这些岩石通过相同的过程变形，特别是在地震断层和诱发地震活动区周围。地球科学和工程研究人员团队将与其他项目合作，扩大妇女和其他未被充分代表的群体在研究和工程方面的参与。大多数盐的连续介质损伤模型基于扩容边界的概念，没有考虑由裂缝引起的弹性特性的各向异性。细观力学和均匀化原理被成功地用来模拟盐岩的弹塑性行为，但没有被用来检验微结构在变形过程中转变的尺度不变性。该项目的目标是将盐的变形机制和流变行为与微结构的密度和取向分布联系起来。在典型基本体积尺度上的变形区域将被分解成独立的过程(例如，开裂)，每个过程都与不同的微观结构描述符(例如，颗粒长宽比)相关。宏观热力学变量将形式上与微观组织描述符相联系，以检验变形区域中转变点的空间和时间尺度不变性。具体的研究目标是：(1)确定盐微结构的拓扑成分和子成分；(2)确定晶内和晶间裂纹脱粘、张开、闭合和重新结合的能量成本；(3)计算与颗粒和REV尺度下变形机制之间的转变相关的能量阈值；(4)测试转变过程中微结构组织的时间和尺度依赖性；(5)设计在地下储存环境中优化愈合性能的岩盐微结构系统。

Salt rock is used for secure storage of oil, high-pressure gas, and nuclear waste because of its ability to creep and form barriers to gas and fluid flow. However, creep processes near subsurface storage facilities can lead to crack debonding, opening, closure and rebonding that compromise the integrity of flow barriers and stability of engineered structures. Mathematical descriptions of cracking and healing are incompletely developed. This award will support fundamental rock physics and mechanics research to link deformation by crack debonding, opening and rebonding to microstructures and mechanical variables that govern the time-dependent behavior of salt rock over geological space and time scales. Deformation of salt occurs rapidly at laboratory conditions making it a good analog to study damage and healing in other crystalline materials and porous media. Project findings are expected to advance quantitative relations enabling accurate modeling and prediction of behaviors in engineering projects. The work will advance fundamental understanding of cracking and healing in other rocks that deform by the same processes, especially around earthquake faults and zones of induced seismicity. The team of geoscience and engineering researchers will collaborate with other programs to broaden the participation of women and other under-represented groups in research and engineering.Most continuum damage models for salt are based on the concept of dilatancy boundary, and do not account for crack-induced anisotropy of elastic properties. Micro-mechanics and homogenization principles were successfully employed to model salt rock elastoplastic behavior, but were not used to test scale invariance of microstructure to transitions in deformation regimes. The goal of this project is to link salt deformation regimes and rheological behaviors with the density and orientation distribution of microstructures. Deformation regimes at the scale of a Representative Elementary Volume will be decomposed into independent processes (e.g., cracking), each related to different microstructure descriptors (e.g., grain aspect ratio). Macroscopic thermodynamic variables will be formally related to the microstructure descriptors to test the space and time scale invariance of transition points in deformation regimes. Specific research objectives are to: (1) Identify topological components and subcomponents of salt microstructure; (2) Determine the energy cost of intra- and inter-granular crack debonding, opening, closure and rebonding; (3) Compute energy thresholds associated with transitions between deformation regimes at the grain and REV scales; (4) Test the time and scale dependence of microstructure organization during transitions; (5) Design rock salt microstructural systems that optimize healing properties in subsurface storage environments.