Calibration of Soil Contact Parameters for Planting Sand Shrubs in the Desert Regions of Inner Mongolia

This study addresses the need for an accurate and reliable discrete element model to understand the interaction between soil particles and planting mechanisms during the operation of watering drilling machines used for cultivating xerophytic shrubs in the desert regions of Inner Mongolia. Focusing on soil from the northwestern desert of Inner Mongolia, we calibrated the parameters pertinent to desert soil. Through Plackett-Burman experiments, we identified key factors that significantly affect the angle of repose. The range of these significant factors was further refined using steepest ascent experiments. Subsequently, a Box-Behnken experiment was conducted to establish a regression model for these significant factors, aiming to identify the optimal combination. We validated this optimal combination through a blend of simulation and physical experiments. The results reveal that the optimal combination of significant factors, determined from the angle of repose as the response variable, includes a static friction coefficient of soil-soil at 0.442, a rolling friction coefficient of soil-soil at 0.140, and a static friction coefficient of soil-steel at 0.305. By using the opening diameter and effective depth of the drilling machine as measurement benchmarks, the relative errors for the simulation and physical experiments were recorded at 2.9 % and 0.3 %, respectively. These findings affirm the accuracy and reliability of the measured parameters, thereby providing a theoretical foundation for understanding the interaction mechanisms between desert planting machinery and soil.