密实散粒体宏微观特性的直剪试验离散元数值分析  

DEM simulation of macro-micro mechanical properties of dense granular materials in direct shear test

作　　者：蒋明镜[1,2] 王富周[1,2,3] 朱合华[1,2] 胡海军[1,2] 赵涛[1,2] 

机构地区：[1]同济大学地下建筑与工程系,上海200092 [2]同济大学岩土及地下工程教育部重点实验室,上海200092 [3]上海建工(集团)总公司技术中心,上海200083

出　　处：《河海大学学报（自然科学版）》2010年第5期538-544,共7页Journal of Hohai University(Natural Sciences)

基　　金：国家自然科学基金(50679057;10972158)

摘　　要：为了分析直剪试验中试样内部的应力、应变状态,采用离散元商业软件PFC2D在不同围压下对密实散粒体进行了大量的数值模拟,分析了试验的边界效应,应力偏转,应力、应变路径以及颗粒群的微观运动状态.模拟结果表明:边界摩擦影响室内直剪试验的测试结果,所得密实散粒体的强度指标偏高,内摩擦角存在1.5°的误差;剪切过程中,主应力大小和方向均发生变化,中心点主应力偏转约44°.由剪切带内外颗粒运动状态和应力、应变路径分析可知,剪切带内部是主要的剪胀区,存在大幅度的加卸载反应,并且应力路径峰值超出了试样峰值强度包线;剪切带外体变较小,主要处于加载状态,应力路径峰值未超出试样残余强度包线.In order to analyze the stress-strain states of granular materials in direct shear test,a large number of numerical investigations were carried out using the DEM commercial software PFC2D.The boundary effect,stress rotation,stress-strain paths and microscopic motion of particles in samples were studied.The simulated results show that the friction between the sample and the shear box has influences on the results of laboratory direct shear test,the yielded strength index of dense granular materials is a bit large,and the friction angle is overestimated by 1.5°.Both the direction and magnitude of the principal stresses change during shearing with the direction rotating about 44° in the center of the sample.The analyses of the particle motions and stress-strain paths demonstrate that the shear dilatation and significant loading-unloading cycles are observed in the shear band while both the volumetric strain change and unloading behavior are slight in the shear band.In addition,the stress path in the shear band may exceed the peak strength envelope while the soil out of the shear band only experiences the stress path below the residual strength envelope.

关 键 词：离散元 密实散粒体 分层欠压法 应力偏转 应力路径 

分 类 号：TU457[建筑科学—岩土工程]