Nguyen T T T, Doanh T, Le Bot A, Dalmas D
Ecole Nationale des Travaux Publics de l'Etat, LGCB, LTDS (UMR 5513), Vaulx en Velin, France.
Ecole Centrale de Lyon, LTDS (UMR 5513), Ecully, France.
Sci Rep. 2021 Feb 3;11(1):2902. doi: 10.1038/s41598-021-82581-x.
We report high-temporal-resolution observations of the spontaneous instability of model granular materials under isotropic and triaxial compression in fully drained conditions during laboratory tests representative of earthquakes. Unlike in natural granular materials, in the model granular materials, during the first stage of the tests, i.e., isotropic compression, a series of local collapses of various amplitudes occurs under random triggering cell pressures. During the second stage, i.e., shearing under triaxial compression, the model granular samples exhibit very large quasiperiodic stick-slip motions at random deviatoric triggering stresses. These motions are responsible for very large stress drops that are described by power laws and are accurate over more than 3 decades in logarithmic space. Then, we identify the quasideterministic nature of these stick-slip events, assuming that they are fully controlled by the cell pressure and solid fraction. Finally, we discuss the potential mechanisms that could explain these intriguing behaviors and the possible links with natural earthquakes.
我们报告了在代表地震的实验室测试中，在完全排水条件下，模型颗粒材料在各向同性和三轴压缩下自发不稳定性的高时间分辨率观测结果。与天然颗粒材料不同，在模型颗粒材料中，在测试的第一阶段，即各向同性压缩期间，在随机触发的单元压力下会发生一系列不同幅度的局部坍塌。在第二阶段，即三轴压缩下的剪切过程中，模型颗粒样本在随机偏应力触发下表现出非常大的准周期粘滑运动。这些运动导致了非常大的应力降，这些应力降由幂律描述，并且在对数空间中超过3个数量级都是准确的。然后，我们确定了这些粘滑事件的准确定性本质，假设它们完全由单元压力和固体分数控制。最后，我们讨论了可能解释这些有趣行为的潜在机制以及与天然地震的可能联系。
