Determination of discrete element model parameters for soil-bulldozer blade interaction

Modeling soil-tillage interaction using a bulldozer blade is a complicated task, involving many factors, such as ground layout, soil strength, heap build-up in front of the tool, soil flow, and cracks in the soil which may occur during blade work. The discrete element method (DEM) is a numerical tool designed to model granular materials. Soil, and particularly sandy soil, may be described as a granular material. Therefore, DEM seems to be a promising tool for modeling the interaction between blade and soil. The model parameters are usually set using a trial and error process, as there is no robust theory for determining the soil parameters of the model. This paper suggests a method for determining the parameters for the DEM model and simulates the soil-blade interaction of cohesionless soil, as a case study, using a 2D DEM program (PFC2D). The method is based on the interlocking property of the particles. The maximum error of the DEM simulation using the recommended parameters compared with the actual soil parameter was 22.8%. Selecting the optimum sprig constant reduces the error to 5%. Two-dimensional simulations were performed of a bulldozer blade moving in a medium of 54, 000 particles, working at different angles, depths, and in different soil parameters. In prediction of the results using McKyes's calculation model, the average difference between the two methods was 7.24% in draft forces (DEM prediction was higher) and 1.55% in the vertical direction. The failure line was defined according to the differences in particle velocities; the results fit the prediction of the failure line according to McKyes. The contribution of the paper lies in the use of DEM as a qualitative and quantitative predictive simulation tool.