摘要
在基于离散元理论以及已有的室内实验成果的基础上,提出一种确定非饱和土体宏观参数与细观参数对应关系的方法,即以结构屈服应力为中间变量构建颗粒间黏结强度与含水率之间的对应关系,并通过编制柔性边界程序,加入到PFC3D(Particle Flow Code in three dimensions)程序中,建立了非饱和土三维离散元模型.进行了不同含水率的非饱和土三轴固结排水剪切试验数值模拟研究,探讨了非饱和土强度、变形、破坏等宏观力学特性的内在细观演化机理和利用离散元法研究非饱和材料的可行性.结果表明:随着含水率的增大,试样内部的颗粒间的接触力越小,受力的土颗粒数目也会减低,而黏结破坏点也会越早出现,并且剪切过程中黏结破坏数量变化可分为3个阶段:缓慢增长阶段、快速发展阶段和残余阶段,从细观角度揭示了土体宏观强度参数随含水率变化的原因;所建立的离散元模型及分析程序在与非饱和土的室内试验结果的对比中,在偏应力—轴应变关系,强度特性等方面表现出了较好的适用性.
Based on the discrete element theory and the existing laboratory experimental results,a method to determine the corresponding relationship between macro parameters and grain-scale parameters of unsaturated soil is proposed,that is,taking the structural yield stress as the intermediate variable,the corresponding relationship between the bond strength and water content between particles is constructed,and a flexible boundary program is compiled and added to PFC3D(particle flow code in three dimensions).Three dimensional discrete element model of unsaturated soil is established in the program of dimensions.The numerical simulation of triaxial consolidation drained shear test of unsaturated soil with different water content is carried out.The internal grain-scale evolution mechanism of macro mechanical properties such as strength,deformation and failure of unsaturated soil is deeply studied.The feasibility of using discrete element method to study unsaturated materials is also discussed.The results show that:with the increase of water content,the smaller the contact force between particles in the sample is,the less the number of soil particles under stress will be,and the earlier the bond failure point will appear.In addition,the change of bond failure number in the shear process can be divided into three stages:slow growth stage,rapid development stage and residual stage.Compared with the laboratory test results of unsaturated soil,the established DEM model and analysis program show good applicability in the aspects of deviatoric stress-strain relationship and strength characteristics.
作者
蔡国庆
李继光
许自立
何旭珍
赵成刚
CAI Guoqing;LI Jiguang;XU Zili;HE Xuzhen;ZHAO Chenggang(Key Laboratory of Urban Underground Engineering of Ministry of Education,BeijingJiaotong University,Beijing 100044,China;School of Civil Engineering,Beijing Jiaotong University,Beijing 100044,China;School of Civil and Environmental Engineering,University of Technology Sydney,Sydney 2007,Australia)
出处
《应用基础与工程科学学报》
EI
CSCD
北大核心
2020年第6期1447-1459,共13页
Journal of Basic Science and Engineering
基金
国家自然科学基金优秀青年基金项目(51722802)
国家自然科学基金面上项目(52078031)
国家自然科学基金高铁联合基金重点支持项目(U1834206)
北京市自然科学基金面上项目(8202038)
关键词
非饱和土
三维离散元数值模拟
宏细观参数
强度特性
含水率
颗粒间黏结强度
三轴剪切
unsaturated soils
PFC3D
macroscopic and grain-scale parameter
strength property
water content
bond strength between particles
triaxial shear
作者简介
蔡国庆(1983—),男,教授,博士生导师.E-mail:guoqing.cai@.bjtu.edu.cn
