Title: The influence of grain crushing and pore collapse on the formation of faults Show Chinese title

Title: 颗粒破碎和孔隙坍塌对断层形成的影响

Abstract: During an earthquake, slip occurs in a localised shear zone that features a heavily granulated fault core that can be characterised as a shear band. We study the formation of this fault core in a granular rock such as sandstone by developing a model of crushable granular media within the framework of Breakage Mechanics. This model accounts for the evolution of the grain size distribution, while also accounting for the co-evolution of the solid fraction. An enrichment with the Cosserat continuum allows for the model to predict finite-width shear bands. The model is then calibrated against experimental data taken from tests on Bentheim sandstone, and a parametric study of the mechanical parameters is conducted using linear stability analysis. We find that for deeply-buried rocks the shear bands have a compactive component, and the initial value of the solid fraction does not play a strong role in the initial band thickness, but can influence the rate of delocalisation of the band. Post-localisation behaviour is studied with the finite element method, which shows the formation of zones of dilation outside the band in addition to the compaction within the band. Using a modified Kozeny--Carman permeability law, it is shown that within the band the permeability reduces by several orders of magnitude, but can increase outside the band. Our results highlight the importance of modelling grain size and solid fraction evolution as they exert a controlling influence on hydromechanical properties that play an important role in fault formation and seismic slip. Show Chinese abstract

Abstract: 在地震期间，局部剪切带中会发生滑动，该剪切带具有一个高度颗粒化的断层核心，可以被描述为剪切带。我们通过在破碎力学框架内开发可破碎颗粒介质的模型，研究了如砂岩这样的颗粒岩石中该断层核心的形成。该模型考虑了粒径分布的演变，同时考虑了固体分数的共同演变。通过引入Cosserat连续体，使模型能够预测有限宽度的剪切带。然后将该模型与来自Bentheim砂岩测试的实验数据进行校准，并使用线性稳定性分析对机械参数进行了参数研究。我们发现，对于深埋岩石，剪切带具有压缩成分，初始固体分数在初始带厚度中不起重要作用，但可能会影响带的去局部化速率。通过有限元方法研究了局部化后的行为，结果表明除了带内的压缩外，还形成了带外的膨胀区域。使用修改后的Kozeny--Carman渗透率定律表明，在带内渗透率减少了几个数量级，但在带外可能会增加。我们的结果突显了建模粒径和固体分数演变的重要性，因为它们对水力机械性质起着控制作用，在断层形成和地震滑动中起着重要作用。