Modelling approach for soil displacement in tillage using discrete element method

The majority of studies dedicated to the dynamic behaviour of agricultural soils are basically focused on prediction of physical conditions within the soil-tool interface whereas the dynamic soil response, such as soil displacement, has not attracted sufficient attention. Considering its importance for engineering applications, the objective of the presented study was to develop a modelling approach to study the soil displacement due to soil interaction with operating tool during sweep cultivation. The developed approach employs the similarity criteria to account for the effect of scaling-up soil particle sizes on model quality and combines (i) an empirical study of soil displacement during a sweep operation and (ii) related numerical simulations using a discrete element model. Soil displacement for three different soil types in soil bins was measured using a tracer methodology. The discrete element model was formulated for cohesive soils with parallel bond contacts between aggregates. The model allows simulation of mechanical tests (used for calibration purposes) and simulation of soil interaction with operating tool during sweep cultivation. This work shows that due to the necessary change in particle sizes of model soil, the conditions of physical equivalence between the model and natural soil can be difficult to satisfy. Such condition can cause significant dissimilarity between measured and simulated soil displacement. However, this can be overcome if the model scaling does not exceed a certain limit which is determined by soil structure and the potential contact density on a tool's contact surface during the soil-tool interaction. By using these findings, our simulations demonstrate that prediction of soil displacement is possible within the suggested approach with sufficient accuracy.