EAGER: Developing an Experimental Technique for Measuring Very Slow Crack Velocities in Rock Using the Atomic Force Microscope

EAGER：开发一种使用原子力显微镜测量岩石中极慢裂纹速度的实验技术

• 批准号: 1301821
• 负责人: John Kemeny
• 金额: $ 4.82万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-11-15 至 2014-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1301821&HistoricalAwards=false
• 关键词: EAGER; Developing; Experimental; Technique; Measuring

Subcritical crack growth is one of the dominant mechanisms for time-dependent rock degradation and failure. In spite of the substantial amount of work that has been conducted on subcritical crack growth in rocks, some very important issues still remain. The double torsion test and other conventional techniques for subcritical crack growth testing measure crack velocities between 10-8 and 10-3 m/s. Within this range, it is not possible to determine the shape of the crack velocity vs. KI curve for very low crack velocities, which is needed in order to accurately predict the long term behavior of geologic structures subjected to low stresses. Also, there is controversy about the origin of shear crack growth in rocks that cannot be adequately resolved with traditional microscopy. To address these issues, experimental techniques based the Atomic Force Microscope (AFM) will be developed. The resolution of the AFM for crack growth measurements is less than 4 nanometers, which allow crack velocities as small as 10-13 m/s to be measured. This will provide fundamental information on the shape of the crack velocity vs. KI curve and the subcritical cutoff for rocks. The experimental procedure developed will involve periodic mechanical loading of small rock samples to create very small amounts of crack growth, followed by AFM investigations to measure the amount and pattern of crack growth. Laboratory and AFM techniques developed for mode I crack growth in glass will initially be used for the rock specimens, and modifications will be made to account for the complex rock microstructure and also to investigate both tensile and shear crack growth. The research will increase our ability to predict the long-term stability of critical geologic structures such as dam foundations, tunnels, underground nuclear waste storage facilities, underground CO2 sequestration sties, highway slopes, and many other structures. Also, the results could impact other science and engineering fields that are interested in environmentally assisted crack growth and failure, such as material science, fracture mechanics, mining, and civil and mechanical engineering. By disseminating the results of this research through international publications and distance courses, this research will be part of the training for undergraduate and graduate students worldwide.

亚临界裂纹扩展是岩石随时间变化的主要破坏机制之一。尽管对岩石中亚临界裂纹扩展进行了大量的研究工作，但仍存在一些非常重要的问题。 用于亚临界裂纹扩展测试的双扭转测试和其它常规技术测量10-8和10-3 m/s之间的裂纹速度。 在这个范围内，不可能确定非常低的裂纹速度的裂纹速度对KI曲线的形状，这是为了准确预测经受低应力的地质结构的长期行为所需要的。 此外，有争议的起源剪切裂纹生长的岩石，不能充分解决与传统的显微镜。 为了解决这些问题，将开发基于原子力显微镜（AFM）的实验技术。 用于裂纹生长测量的AFM的分辨率小于4纳米，这允许测量小至10-13 m/s的裂纹速度。 这将提供关于裂纹速度与KI曲线的形状和岩石的亚临界截止的基本信息。 开发的实验程序将涉及周期性的机械加载的小岩石样品，以创建非常少量的裂纹生长，然后由AFM调查，以测量裂纹生长的数量和模式。 实验室和原子力显微镜技术开发的模式I裂纹生长玻璃将最初用于岩石标本，并修改将考虑复杂的岩石微观结构，也调查拉伸和剪切裂纹的增长。这项研究将提高我们预测关键地质结构长期稳定性的能力，如坝基、隧道、地下核废料储存设施、地下二氧化碳封存站、公路边坡和许多其他结构。 此外，这些结果可能会影响其他对环境辅助裂纹生长和失效感兴趣的科学和工程领域，如材料科学，断裂力学，采矿以及土木和机械工程。 通过国际出版物和远程课程传播这项研究的结果，这项研究将成为全世界本科生和研究生培训的一部分。