散粒体介质剪切变形的宏观特征与细观机制

Studies on the Macro Characteristics and Meso Mechanism of Shear Deformation in Granular

为了探究散粒体介质在剪切过程中的内部结构变化及细观变形破坏特征,开展了直剪数值模拟试验,对剪切过程中颗粒体系的变形特性进行研究。试验中观察了散粒体内部结构随外荷载的变形响应情况,分析了试样的应力应变及剪胀特征关系。结果表明:散粒体的剪切变形及破坏是一个累积增长的过程,颗粒试样具有明显的应变软化现象,且在剪切面附近发生局部化塑性变形,同时整体表现出剪胀性;剪切过程中试样的细观组构各向异性与剪应力的变化具有一致性;接触力链网络演化呈现出强力链发育且主要集中于剪切面区域内的规律;颗粒的接触平均配位数整体呈现出减小的规律。

In order to explore the internal structure change and meso-deformation failure response mechanism of granular medium in the shear process,this paper carried out direct shear numerical simulation test based on the discrete element method,and established an experimental model by using the particle flow software PFC to study the mechanical characteristics of the particle system in the shear process.Before the test,the samples inside the shear box were stained and marked to observe the deformation response of the internal structure of the granular body with the external load.The corresponding data of stress displacement were recorded,and the relationship between stress strain and dilatancy characteristics was analyzed.The testing results show that the deformation and shear failure of granular particles is a process of cumulative growth,and the granular samples show obvious strain softening and localized plastic deformation near the shear surface,while showing overall dilatancy.The microstructure anisotropy and shear stress change synchronously during the shearing process.The evolution of the contact force chain network also shows a special regularity,that is,the strong chain develops and mainly concentrates in the shear plane region.The average contact coordination number of particle samples shows a decreasing trend.The series of macroscopic and microscopic mechanical characteristics indicate the synchronicity of the sample with external load.