Quantifying Patterns of Brittle Damage in Fractured Rock

裂缝控制着地壳中流体的流动--这对于碳氢化合物的产生、地下废物储存的规划以及对地震的理解都是至关重要的。裂隙岩石的强度或软弱取决于裂隙中流体的压力和裂隙的模式。在最简单的情况下，在一块充满球形流体的岩石中，孔隙流体压力的变化在各个方向上都能感受到同样的变化。这被称为各向同性孔弹性。然而，众所周知，破碎的岩石包含一系列狭窄的裂缝，其中许多裂缝的方向是相似的。这表明，孔隙流体压力的变化在所有方向上都不会被均匀地感受到，这已经由各向异性孔弹性理论来描述。这个项目的目的是检验各向异性孔弹性假说：主要是，流体饱和岩石中应力的变化取决于岩石中的裂隙模式。到目前为止，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。该项目将收集破裂岩石的裂缝模式的定量数据，然后预测随着流体压力的变化而发生的应力变化。这些预测将与通常使用的各向同性情况进行比较，差异将被量化。这项建议中描述的研究将显著改进我们的流体饱和裂隙岩石的力学模型，从而更有效地管理地下资源，并更好地评估地震危险和废物设施故障的风险。

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.