Discrete element modelling of soil pressure under varying number of tire passes

Pressure imposed on an arable farmland by farm machinery can lead to severe soil compaction. A model was developed with Discrete Element Method (DEM) to simulate soil – tire interaction. Virtual dead weight method was performed for the purpose of model calibration. Simulated soil pressure data were obtained from the topsoil layer under varying number of tractor tire passes (1P, 2P, 3P, 4P, 5P, 6P, 7P and 8P). Simulation results were validated with maximum soil pressure data from a field experiment in which soil pressure was measured at 0.1 m depth in sandy loam soil. Model results of maximum soil pressure increased from 137.7 to 242.5 kPa when the number of passes increased from 1P to 8P. Prediction of the maximum soil pressure was reasonably accurate for 1P and 2P with Relative Mean Errors (R.M.E) less than 9%. Predictions for 3P to 8P had higher R.M.E. In terms of model application, soil sinkage and rolling resistance ranged from 0.07 to 0.14 m and 225.3 to 517.8 N respectively between one to eight passes. The model developed in this study can be used in the simulation of soil pressure distribution and deformation in the topsoil layer induced by heavy farm machinery.