Patton Andrew, Goebel Thomas, Kwiatek Grzegorz, Davidsen Jörn
Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW Calgary, Alberta T2N 1N4, Canada.
Center for Earthquake Research and Information, University of Memphis, 3890 Central Avenue, Memphis, Tennessee 38152, USA.
Phys Rev E. 2023 Jul;108(1-1):014131. doi: 10.1103/PhysRevE.108.014131.
Externally stressed brittle rocks fail once the stress is sufficiently high. This failure is typically preceded by a pronounced increase in the total energy of acoustic emission (AE) events, the so-called accelerated seismic release. Yet, other characteristics of approaching the failure point such as the presence or absence of variations in the AE size distribution and, similarly, whether the failure point can be interpreted as a critical point in a statistical physics sense differs across experiments. Here, we show that large-scale stress heterogeneities induced by a notch fundamentally change the characteristics of the failure point in triaxial compression experiments under a constant displacement rate on Westerly granite samples. Specifically, we observe accelerated seismic release without a critical point and no change in power-law exponent ε of the AE size distribution. This is in contrast to intact samples, which exhibit a significant decrease in ε before failure. Our findings imply that the presence or absence of large-scale heterogeneities play a significant role in our ability to predict compressive failure in rock.
一旦应力足够高，外部受力的脆性岩石就会发生破坏。这种破坏通常在声发射（AE）事件的总能量显著增加之前出现，即所谓的加速地震释放。然而，接近破坏点的其他特征，如AE尺寸分布是否存在变化，以及类似地，破坏点是否可以在统计物理学意义上被解释为临界点，在不同实验中有所不同。在这里，我们表明，在对韦斯特利花岗岩样品进行恒位移速率的三轴压缩实验中，缺口引起的大规模应力不均匀性从根本上改变了破坏点的特征。具体而言，我们观察到加速地震释放但没有临界点，且AE尺寸分布的幂律指数ε没有变化。这与完整样品形成对比，完整样品在破坏前ε会显著降低。我们的研究结果表明，大规模不均匀性的存在与否在我们预测岩石压缩破坏的能力中起着重要作用。
