Catastrophic Failure: what controls precursory damage localisation in rocks?

从人为地震活动到自然滑坡、火山爆发和地震，灾难性破坏是脆性地球在各种尺度上的一个至关重要的现象。它总是与局部变形带上较小的断层和断裂形式的结构破坏集中有关，最终导致沿明显的突发性断层面发生系统级脆性破坏。然而，局部化的过程还没有被很好地理解——较小的裂缝沿着早期的断层自发地自组织，通常是在失效之前，但所涉及的精确机制尚未确定。许多问题仍然存在，包括：Q1 -裂纹、孔隙和晶界如何与局部应力场相互作用，导致在特定地点、方向和时间发生灾难性破坏？是什么决定了准静态和动态过程的相对重要性？Q3 -为什么我们只能在某些情况下检测到灾难性故障的前兆？在这里，我们将直接通过成像整个定位过程来解决这些问题，使用新开发的x射线透明变形细胞和快速同步加速器x射线微断层扫描。我们将首次在同步加速器中以高分辨率在结构上和地震上一起可视化定位过程的性质和演变。我们将故意放慢这一过程，以成像其演变，并利用快速电子监测和反馈控制来研究潜在机制的应变率依赖性。这将提供对相关机制的前所未有的直接观察，包括地震（产生声发射的局部裂缝）和地震（弹性载荷和无声不可逆损伤）过程对结果的贡献。这种技术的创新组合是及时的，可行的，并且很可能改变我们对微观过程在控制系统大小故障中的作用的理解。研究结果将为自然和人为地震活动的类似过程提供解释模型，包括对管理大型诱发事件风险的战略进行比例模型试验。

Catastrophic failure is a critically-important phenomenon in the brittle Earth on a variety of scales, from human-induced seismicity to natural landslides, volcanic eruptions and earthquakes. It is invariably associated with the structural concentration of damage in the form of smaller faults and fractures on localised zones of deformation, eventually resulting in system-sized brittle failure along a distinct and emergent fault plane. However, the process of localisation is not well understood - smaller cracks spontaneously self-organise along the incipient fault plane, often immediately before failure, but the precise mechanisms involved have yet to be determined. Many questions remain, including : Q1 - How do cracks, pores and grain boundaries interact locally with the applied stress field to cause catastrophic failure to occur at a specific place, orientation and time?; Q2 what dictates the relative importance of quasi-static and dynamic processes?; and Q3 - why can we detect precursors to catastrophic failure only in some cases? Here we will address these questions directly by imaging the whole localisation process, using a newly-developed x-ray transparent deformation cell and fast synchrotron x-ray micro-tomography. We will visualise the nature and evolution of the localisation process structurally and seismically together for the first time at high resolution in a synchrotron. We will deliberately slow the process to image its evolution, and to investigate the strain-rate dependence of the underlying mechanisms, using rapid electronic monitoring and feedback control. This will provide unprecedented direct observation of the relevant mechanisms, including the contribution of seismic (local cracking producing acoustic emissions) and aseismic (elastic loading and silent irreversible damage) processes to the outcome. This innovative combination of techniques is timely, feasible, and is likely to transform our understanding of the role of microscopic processes in controlling system-size failure. The results will provide interpretive models for similar processes in natural and human-induced seismicity, including scale-model tests of strategies for managing the risk of large induced events.