We quantitatively investigate the spatial stress variations within the fault zone rock mass by explicitly incorporating macroscopic fractures into a 2D multilayer model. Based on elastic crack theory, we first derive a unified constitutive law for frictional fractures, featuring elastic and plastic shear deformation and shear-induced dilatancy. To honor the varying degrees of damage across fault zones, the multilayer model is composed of varying densities of randomly oriented frictional fractures from layer to layer. Under the boundary conditions specific to fault zones, the global mechanical response of each layer is quantitatively related to the local fracture deformation. We show that the major principal stress always rotates toward a limiting angle of 45° with respect to the fault plane and that the differential stress invariantly decreases with increasing fracture density. Approaching the fault core, the mean stress can either increase or decrease, depending on whether the fault strikes at a high (>45°) or low (<45°) angle to the regional major principal stress. Accumulated damage also results in the decrease and increase of the effective Young's modulus and Poisson's ratio of the fractured rock mass, respectively. Both the fracture properties and pore pressure affect the stress variations by modulating the fracture-associated deformation and the relative proportion of the elastic and plastic components. Our model illuminates the systematic variations of in situ stresses and effective elastic properties within the damage zone of a mature fault.

中文翻译：

---

地应力如何在断层带内旋转？从摩擦、破裂岩体的显式建模中获得的见解

我们通过将宏观裂缝明确地结合到二维多层模型中来定量研究断层带岩体内的空间应力变化。基于弹性裂纹理论，我们首先推导出了摩擦断裂的统一本构律，其特征是弹性和塑性剪切变形和剪切引起的剪胀。为了尊重断层带不同程度的损伤，多层模型由不同密度的随机取向的摩擦裂缝逐层组成。在特定于断层带的边界条件下，每一层的整体力学响应与局部断裂变形定量相关。我们表明，主要主应力总是朝着相对于断层面 45° 的限制角旋转，并且微分应力随着裂缝密度的增加而不变地减小。接近断层核心时，平均应力可以增加或减少，这取决于断层与区域主要主应力的角度是高 (>45°) 还是低 (<45°)。累积损伤还分别导致破裂岩体的有效杨氏模量和泊松比的减少和增加。断裂特性和孔隙压力都通过调节与断裂相关的变形和弹性和塑性成分的相对比例来影响应力变化。