滇中地区坡耕地红黏土离散元仿真模型参数标定与试验

Parameter Calibration for Discrete Element Simulation of Red Clay Soils in Sloping Cropland in Central Yunnan

摘要:

适用于山区坡耕地的耕整地机械在优化设计过程中缺乏准确的离散元仿真模型参数，制约了机具的设计改进。以滇中地区坡耕地红黏土为研究对象，结合无侧限抗压强度试验和离散元仿真方法，建立了基于EEPA模型和Bonding模型的无侧限抗压强度试验仿真模型，并对仿真模型中的相关参数进行标定。试验中土样断裂的最大轴向压力平均值为431.19 N。以最大轴向压力为响应值设计Plackett-Burman试验、Steepest Ascent试验和Box-Behnken试验来确定离散元仿真模型参数，并通过试验来验证仿真的可靠性。Bonding模型单位面积法向刚度X1为3.14×108 N/m3、临界法向应力X3为53 175.4 Pa、EEPA模型接触塑性比X6为0.318 24。在该参数组合下进行验证仿真，其最大轴向压力与试验的相对误差仅为1.71%，并且Bond键的断裂面与试验相比较为符合。仿真与试验所得到的数据基本一致，说明该参数组合可靠，可为后续红黏土的离散元仿真提供理论依据。

Abstract:

Aiming at the problems of insufficient parameters and inaccurate simulation in discrete element simulation for Yunnan red clay soil, taking the red clay soil of sloping cultivated land in central Yunnan as the research object, the simulation model of the unconfined compressive strength test based on the EEPA model and the Bonding model was established by combining the unconfined compressive strength test and the discrete element simulation method, and the relevant parameters in the simulation model were calibrated. The maximum axial pressure of soil sample fracture in the unconfined compressive strength test was 431.19 N. The Plackett-Burman test was designed with the maximum axial pressure as the response value to screen out the factors that had a highly significant influence on the response value, and the optimal parameters of the highly significant factors were determined by the Steepest Ascent test and Box-Behnken test. The results were as follows: the normal stiffness per unit area of the Bonding model X1 was 3.14×108 N/m3, the critical normal stress X3 was 53 175.4 Pa, and the contact-plasticity ratio of the EEPA model X6 was 0.318 24. In the validation simulation under this parameter combination, the relative error between the maximum axial pressure and the test was only 1.71%, and the fracture surface of the bonding Bond was compared favorably with the test. The data obtained from the simulation were consistent with the test, indicating that the parameter combination was reliable and can provide a theoretical basis for the subsequent discrete element simulation of red clay.