颗粒形状对粗粒土剪切变形影响的细观研究

A meso-scale study of the influence of particle shape on shear deformation of coarse-grained soil

颗粒形状是影响粗粒土密实度、力学与渗流等特性的主要因素之一。为了分析颗粒形状对粗粒土剪切特性的影响,采用离散元法生成4种不同形状的颗粒组,进行粗粒土直剪试验模拟与剪切宏细观响应研究,得出了颗粒形状对剪应力-剪位移、体应变-剪位移的影响,分析了粗粒土剪切应力、应变特性与剪胀特性。通过分析剪切带厚度、颗粒旋转量值、平均接触数、孔隙率及接触力系等宏细观参量的演化规律,研究颗粒形状在宏细观尺度上对粗粒土的影响。研究表明:异形颗粒间的咬合自锁作用大于纯圆颗粒,试样的抗剪强度有随形状系数的减小而增大的趋势。试样颗粒在外荷载作用下发生运动,应变主要表现在颗粒运动剧烈、剪胀幅度较大的剪切带内。颗粒形状系数F减小,试样的初始平均接触数增加,内摩擦角φ增大,剪切带内孔隙率增量越大,剪胀幅度越大。剪切过程中强力链聚集于剪切带内并起骨架作用,随着形状系数的减小,力链长度在0~5所占百分比呈增大趋势;剪切带内强力链的数目随着形状系数的减小而增加,峰值含量在30%~35%之间。

Particle shape is one of the main factors that affect the compactness,mechanics and seepage of coarsegrained soil.In order to analyze the influence of particle shape on the shear characteristics of coarse-grained soil,the discrete element method is used to generate four different particle groups.The direct shear test simulation and macro-micro shear response research of coarse-grained soil are carried out.The influence of particle shape on shear stress-shear displacement and volume strain-shear displacement is obtained.The shear stress,strain characteristics and dilatancy characteristics of coarse-grained soil are analyzed.The influence of particle shape on coarse-grained soil on macro-micro scale is studied by analyzing the evolution law of macro-micro parameters such as shear zone thickness,particle rotation value,average contact number,porosity and contact force system.The results show that the self-locking effect of the special-shaped particles is greater than that of the pure round particles,and the shear strength of the sample tends to increase with the decreasing shape coefficient.The sample particles move under the action of external load,and the strain is mainly shown in the shear zone where the particles move violently and dilate greatly.The particle shape coefficient decreases,the initial average contact number of the sample increases, the internal friction angle "φ" increases, and the larger the increment of porosityin the shear band, the larger the dilatancy amplitude. During the shearing process, the strong chain gathers in theshearing zone and acts as a skeleton. With the decrease in the shape coefficient, the percentage of the force chainlength in the range of 0 - 5 increases. The number of strong chains in the shear band increases with the decrease inthe shape coefficient, and the peak value content ranges between 30% and 35%.