Collaborative Research: Salt Rock Microstructure and Deformation

合作研究：盐岩微观结构与变形

• 批准号: 1362004
• 负责人: Chloe Arson
• 金额: $ 20.01万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1362004&HistoricalAwards=false
• 关键词: Collaborative; Research; Salt; Rock; Microstructure

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.

盐岩可用于安全储存石油、高压气体和核废料，因为它能够蠕变并形成气体和流体流动的屏障。 然而，地下储存设施附近的蠕变过程可能导致裂纹脱粘、张开、闭合和重新粘合，从而损害流动屏障的完整性和工程结构的稳定性。 裂纹和愈合的数学描述尚未完全发展。 该奖项将支持基础岩石物理和力学研究，将裂纹脱粘、张开和再粘结变形与控制盐岩在地质空间和时间尺度上随时间变化的微观结构和机械变量联系起来。 盐的变形在实验室条件下迅速发生，使其成为研究其他晶体材料和多孔介质中的损伤和愈合的良好模拟。 项目研究结果预计将推进定量关系，从而实现工程项目中行为的准确建模和预测。 这项工作将增进对通过相同过程变形的其他岩石的破裂和愈合的基本了解，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，扩大女性和其他代表性不足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都基于剪胀边界的概念，并且不考虑裂缝-引起的弹性各向异性。微观力学和均质化原理已成功用于模拟盐岩弹塑性行为，但未用于测试微观结构对变形状态转变的尺度不变性。该项目的目标是将盐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。代表性基本体积尺度的变形机制将被分解为独立的过程（例如裂纹），每个过程都与不同的微观结构描述符（例如晶粒长宽比）相关。宏观热力学变量将与微观结构描述符正式相关，以测试变形状态中转变点的空间和时间尺度不变性。具体研究目标是：（1）识别盐微观结构的拓扑成分和子成分； (2)确定晶内、晶间裂纹脱粘、张开、闭合和再粘结的能量消耗； (3) 计算与晶粒和 REV 尺度上的变形状态之间的转变相关的能量阈值； (4) 测试转变过程中微观组织组织的时间和尺度依赖性； (5) 设计岩盐微结构系统，优化地下储存环境的愈合性能。