单轴压缩下页岩类脆性材料细观损伤演化的离散元分析

Discrete element analysis of meso-damage evolution of shale-like materials under uniaxial compression

了解广泛存在的类似页岩的脆性材料各向异性对工程安全具有重要意义。本研究将页岩视为粘结颗粒材料,基于离散单元方法研究了横观各向同性脆性页岩的损伤演化。再现了不同层理角的页岩试样的破坏模式,并对比了实验和数值模拟的抗压强度和弹性模量。引入微裂纹的概念,通过定义裂纹密度函数,系统地研究了单轴压缩条件下,页岩层理角对细观结构的影响。此外基于平均配位数建立了配位数变化与细观损伤的联系,并根据配位数的变化与裂纹数量将加载过程分为三个阶段,分析了不同阶段配位数与裂纹数量的对应变化关系。研究表明,页岩的裂纹密度随着层理角的增加而增加,而试样的平均配位数在加载过程中先上升后剧烈下降,颗粒集合体在单轴压缩条件下的应力应变及裂纹数量曲线与平均配位数曲线有良好的一致性。该研究揭示了横观各向同性脆性岩石的破坏过程和内在机理,将为页岩类脆性材料的工程应用提供理论指导。

Understanding the anisotropic characteristics of the widespread shale-like brittle materials is of great significance to engineering safety.In this article,shale was considered as a bonded granular material and the damage evolution of transverse isotropic brittle shale was studied based on DEM.The failure modes of shale specimens with different bedding angles were reproduced and the compressive strength and elastic modulus of experimental and numerical simulations were compared.The effect of shale bedding angle on the microstructure under uniaxial compression conditions was systematically investigated by defining the crack density function.In addition,the association of coordination number variation with internal meso-damage was established based on average coordination number.The loading process can be divided into three stages according to the variation of coordination number and the crack number.The corresponding variation of coordination number and the number of cracks in different stages were analyzed.The study shows that the crack density of the shale increases with increasing bedding angle under the same conditions,while the average coordination number of the specimens rises and then decreases sharply during loading,and the stress-strain and crack number curves of the particle aggregates under uniaxial compression are in good agreement with the mean coordination number curve.This research reveals the damage process and the intrinsic mechanism of transverse isotropic brittle rocks,which will provide theoretical guidance for the engineering application of shale-like brittle materials.