用非线性laser干涉法实时观测粒状岩石模拟材料的变形和破坏
Real time observation of granular rock analogue material deformation and failure using nonlinear laser interferometry
摘要：
更好地理解和预测自然过程，如滑坡或地震断层活动，需要岩石力学和地质材料动力学的详细理论和实验分析。近几十年来，岩石颗粒材料的实验研究取得了很大进展，如著名的剪切带实验。取得这一进展的原因之一是观测仪器技术的不断改进。但是，缺乏实时方法不允许检测即将到来的断裂过程的指标，从而预测该现象。在这里，我们已经进行了单轴压缩实验，以分析不同的冲击的粒状岩石材料样品的响应。我们使用一种新的干涉激光传感器的非线性自混合干涉技术的基础上，实时观察样品的变形，并评估其有用性作为诊断工具的分析geomaterial动力学。由于这种方法的高空间和时间分辨率，我们观察到两个振动过程中响应的动态载荷和故障的发生。后者之前是材料的振动周期的连续变化。经过几次冲击，材料的响应不再是可逆的，我们检测到一个渐进的积累不可逆的变形导致的断裂过程。我们表明，材料失效是预期的表面振动运动的临界减速，因此可以设想作为一个早期的警告信号或预测宏观故障的样品。非线性自混合干涉测量技术很容易扩展到故障传播测量。这为岩土材料的变形破坏研究开辟了一个新的观测窗口。
英文摘要：
A better understanding and anticipation of natural processes such as landsliding or seismic fault activity requires detailed theoretical and experimental analysis of rock mechanics and geomaterial dynamics. These last decades, considerable progress has been made towards understanding deformation and fracture process in laboratory experiment on granular rock materials, as the well-known shear banding experiment. One of the reasons for this progress is the continuous improvement in the instrumental techniques of observation. But the lack of real time methods does not allow the detection of indicators of the upcoming fracture process and thus to anticipate the phenomenon. Here, we have performed uniaxial compression experiments to analyse the response of a granular rock material sample to different shocks. We use a novel interferometric laser sensor based on the nonlinear self-mixing interferometry technique to observe in real time the deformations of the sample and assess its usefulness as a diagnostic tool for the analysis of geomaterial dynamics. Due to the high spatial and temporal resolution of this approach, we observe both vibrations processes in response to a dynamic loading and the onset of failure. The latter is preceded by a continuous variation of vibration period of the material. After several shocks, the material response is no longer reversible and we detect a progressive accumulation of irreversible deformation leading to the fracture process. We demonstrate that material failure is anticipated by the critical slowing down of the surface vibrational motion, which may therefore be envisioned as an early warning signal or predictor to the macroscopic failure of the sample. The nonlinear self-mixing interferometry technique is readily extensible to fault propagation measurements. As such, it opens a new window of observation for the study of geomaterial deformation and failure.
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