西南区坡耕地紫色土离散元模型参数标定

Parameter Calibration of Discrete Element Model for Purple Soil on Sloping Farmland in Southwest China

土壤离散元模型是离散元法研究土壤与触土部件相互作用的基础。为了获得西南区坡耕地紫色土离散元模型,本文基于堆积试验,采用EDEM2020软件中的Hertz-Mindlin with JKR接触模型,以休止角为响应值,结合土壤本征参数实测试验,对模型参数进行标定。实测参数包括土壤密度、含水率、休止角、粒径分布、颗粒-颗粒静摩擦系数、颗粒-45钢静摩擦系数,利用Origin2021b软件图像数字化工具处理图像,得到实际休止角为34.11°,变异系数为0.452%。利用Design-Expert11软件设计了Plackett-Burman试验,对影响拟合休止角的9个参数进行筛选,得到4个影响显著参数,即颗粒表面能、颗粒-颗粒滚动摩擦系数、颗粒-45钢静摩擦系数、颗粒-45钢滚动摩擦系数。设计最陡爬坡试验进一步缩小模型参数取值范围,设计Box-Behnken试验,对模型进行分析优化,得到4个参数最优组合,即颗粒表面能0.134 J/m^(2),颗粒-颗粒滚动摩擦系数0.231,颗粒-45钢静摩擦系数1.045,颗粒-45钢滚动摩擦系数0.228。结果表明,仿真休止角与实际休止角相对误差为2.07%,一致性较好,可为紫色土离散元仿真研究提供参考。

Soil model is the basis of studying the interaction between soil and soil-touching parts by using discrete element method.To obtain the soil model for discrete element simulation of purple soil on sloping farmland in Southwest China,this study constructed a simulation parameter calibration experiment based on stacking test in combination with some measured test of soil intrinsic parameters.The calibration experiment took repose angle as the response value and Hertz-Mindlin with JKR embedded in EDEM 2020 as contact model.The density,moisture content,repose angle,particle size distribution of soil,the particle-45 steel static friction coefficient and the particle-particle static friction coefficient were measured.The average repose angle of the actual soil was 34.11°and the coefficient of variation was 0.452%.Using Plackett-Burman Design experiment to screen the key factors affecting the repose angle of purple soil,including particle surface energy,particle-particle rolling friction coefficient,particle-45 steel static friction coefficient and particle-45 steel rolling static friction coefficient.The deepest ascent experiment was designed to narrow down their range of values.Box-Behnken Design experiment was used to analyze and optimize the model,and the optimal values of four significant factors were obtained:particle surface energy 0.134 J/m^(2),particle-particle rolling friction coefficient 0.231,particle-45 steel static friction coefficient 1.045,particle-45 steel rolling friction coefficient 0.228.The verification test showed that the relative error between the simulated repose angle and the measured repose angle was 2.07%,which indicated that the parameters obtained by calibration test was accurate and reliable,which can be used as a reference for the future study of discrete element simulation of purple soil.