Quantifying Patterns of Brittle Damage in Fractured Rock

裂缝控制着地壳中流体的流动——这对于生产碳氢化合物、规划地下废物储存以及了解地震至关重要。破裂岩石的强弱取决于裂缝中流体的压力和裂缝的形态。在最简单的情况下，在具有球形充满流体的孔隙的岩石中，孔隙流体压力的变化在各个方向上都是相等的。这被称为各向同性孔隙弹性。然而，众所周知，断裂的岩石含有一系列狭窄的裂缝，其中许多裂缝的方向相似。这表明孔隙流体压力的变化不会在所有方向上都被同样感受到，这是由各向异性孔隙弹性理论描述的。该项目旨在测试各向异性孔隙弹性的假设：主要是流体饱和岩石中应力的变化取决于岩石中裂缝的模式。迄今为止，还没有根据变形岩石的测量数据对这一理论进行系统评估。该项目将从断裂岩石中收集裂缝模式的定量数据，然后预测应力随流体压力变化的变化。这些预测将与常用的各向同性情况进行比较，并对差异进行量化。本提案所描述的研究将大大改进我们的流体饱和裂隙岩石力学模型，从而更有效地管理地下资源，更好地评估地震危害和废物设施故障风险。

Cracks control the flow of fluids in the Earth's crust - this is critical for producing hydrocarbons, for planning subsurface waste storage and for understanding earthquakes. The strength or weakness of fractured rock depends on the pressure of the fluid in the cracks and the pattern of those cracks. In the simplest case, in a rock with spherical fluid-filled pores, changes in pore fluid pressure are felt equally in all directions. This is known as isotropic poroelasticity. However, fractured rocks are known to contain arrays of narrow cracks, many of which are oriented in a similar direction. This suggests that changes in pore fluid pressure will *not* be felt equally in all directions, and this has been described by a theory of anisotropic poroelasticity. This project aims to test the hypothesis of anisotropic poroelasticity: chiefly, that changes in stress in a fluid saturated rock depend on the pattern of cracks in that rock. To date, there has been no systematic assessment of this theory based on measured data from deformed rocks. This project will collect quantitative data on crack patterns from fractured rocks and then predict changes in stress with changes in fluid pressure. These predictions will be compared to the commonly used isotropic case, and the discrepancy will be quantified. The research described in this proposal will significantly improve our mechanical models of fluid-saturated fractured rock, leading to more efficient management of subsurface resources and better assessment of seismic hazards and risks of waste facility failure.