粗粒土大型直剪试验的二维离散元模拟

通过一组强风化玄武岩粗粒土的室内大型直剪试验，获取其强度、变形等宏观参数。并基于颗粒离散元软件PFC2D，采用圆盘模拟土颗粒建立了考虑级配的二维直剪模型，结果表明：黏结半径因子为0．39时，剪应力一剪位移模拟值与试验值相符较好，垂直位移一剪位移模拟值与试验值之间存在一定的偏差；通过参数校正发现圆盘间摩擦系数随着垂直压力增加而增大，其值介于0．15—0．60；剪切过程造成了接触压力的偏转和集中，剪切缝附近圆盘呈不规则的涡状细观运动。

Two-Dimensional Discrete Element Simulations of Large-scale Direct Shear Tests of Coarse Grained Soils

Coarse-grained soils are extensively used as roadbed embankment material for highway construction in the mountainous areas.To obtain the strength and deformation parameters of coarse-grained soils from highly weathered basalts,a series of laboratory large-scale direct shear tests were conducted.Based on the particle discrete element software PFC2D,a two-dimensional direct shear numerical model was established with soil particles modeled as disks.In the model,the particles size distribution and the parallel bonding contact model(PBM) effects were considered.The direct shear tests were simulated under different vertical pressures.Results indicate that: Under a 1.9×107 N/m of normal and shear stiffness,a magnitude of 8.0×105 N/m for the bond normal and shear stiffness,and 0.39 for the bonding radius multiplier factor,the resulting shear strength indices are 98.33kPa for the cohesion and 27.02° for the internal friction angle,respectively.The shear stress and shear displacement have a good agreement in simulated and tested results.During initial testing,the simulated and tested vertical displacement-shear displacements were different.From parameter calibration,it is noted that the friction coefficient among disks increases when the vertical pressure increases from 0.15 to 0.60.Due to the rotation and the stress concentration of the contact pressure,irregular rotational movements of the disks near the shear band were observed.