基于离散元方法的黏性土剪切特性细观机理  

Mesoscopic Mechanism of Clay Shear Properties Based on Discrete Element Method

作　　者：倪嘉楠 洪勇[1] 姜奕辰 于超 贺可强[1] 李亮[1] Ni Jianan;Hong Yong;Jiang Yichen;Yu Chao;He Keqiang;Li Liang(School of Civil Engineering,Qingdao University of Technology,Qingdao 266525,Shandong,China)

机构地区：[1]青岛理工大学土木工程学院,山东青岛266525

出　　处：《吉林大学学报(地球科学版)》2025年第1期223-232,共10页Journal of Jilin University:Earth Science Edition

基　　金：国家自然科学基金项目(41572259,41272341)。

摘　　要：为了研究黏性土在剪切过程中的细观剪切力学特性,结合室内试验结果和离散元模拟方法对粉质黏土剪切力学性质进行了细观机理分析。首先基于室内试验的结果,通过建立符合黏性土剪切试验特征的PFC 2D模型,对剪切过程中黏性土和砂土的一些细观参数进行比较分析;然后对黏性土在不同剪切阶段细观应力、细观变形以及细观位移进行分析,并从细观角度分析了试样的宏观剪切力学特性。结果表明:黏性土中的剪切应力主要是由颗粒之间的力链提供的,黏性土的颗粒较小,力链较细,所提供的承载力也较小,黏性土力链最大承载力仅约为0.77 kN,而标准砂可以达到1.75 kN;超固结状态下的黏性土在进行剪切时具有明显的应变软化现象,这一现象与颗粒的定向排列以及颗粒之间的强力链数量减少有关;在剪切过程中黏性土中部配位数减少了1.70,这是由于黏性土颗粒发生偏移,颗粒之间的接触形成拱状结构,也导致了孔隙率增大,使得黏性土的体积应变增大;黏性土在剪切过程中,颗粒位移等值线在模型的中部PFC 2D模型形成近似菱形的区域,并且黏性土在剪切破坏时形成的剪切带是一条相对位移基本一致的狭长条带。In order to study the micro shear mechanical properties of clay during the shear process,a micro mechanism analysis of the shear mechanical properties of this silty clay was conducted using laboratory test results and discrete element simulation methods.Based on the results of experiments,a PFC 2D model that conforms to the shear test characteristics of clay was established to compare and analyze some micro parameters of clay and sand during the shear process.Then micro stress,micro deformation,and micro displacement of clay at different shear stages were analyzed,and the macroscopic shear mechanical properties of the sample were analyzed from a micro perspective.The results show that the shear stress in clay is mainly provided by the force chain between particles.The particles in clay are smaller and the force chain is finer,resulting in a lower bearing capacity.The maximum bearing capacity of the force chain in clay is only about 0.77 kN,while standard sand can reach 1.75 kN.Under the condition of overconsolidation,clay exhibits significant strain softening during shearing,which is related to the directional arrangement of particles and the reduction in the number of strong chains between particles.During the shearing process,the middle coordination number of the clay decreased by 1.70,which is due to the displacement of the clay particles,and an arch like structure between the particles were formed to increase the porosity,which results in an increase in the volumetric strain of the clay.During the shearing process of clay,the contour lines of particle displacement form an approximately diamond shaped area in the middle region of the PFC 2D model,and the shear band of clay is a narrow strip with relatively consistent displacement when sheared.

关 键 词：黏性土 砂土 离散元 体积应变 孔隙率 剪切带 PFC 2D模型 

分 类 号：P59[天文地球—地球化学]