Role of particle shape and plant roots in the discrete element model of soil-sweep interaction

This study was an investigation of the interaction of loamy sand and clay loam soils with a sweep under field conditions by studying the role of particle shape utilised in a discrete element method (DEM) model of soil-sweep interaction. Beside the soil modelling a validated DEM model of roots present in the soil was developed which highlighted the role of roots in the soil reinforcement. Using the results of field and laboratory tests, layered DEM model of soil structure was improved. In the DEM soil model developed, Young's modulus in the contacts of particles was selected based on oedometric test as 5 MPa in clay loam and 10 MPa in loamy sand soil. A combined calibration process was performed in three different assemblies composed of clumps or spheres, where a DEM model of cone penetration tests' and a soil-sweep DEM model were applied together to confirm the adequate utilisation of layers with different cohesive and frictional parameters. Clumps were utilised for modelling clay loam soil, while for loamy sand spheres were utilised. The geometry of the utilised particles corresponds to the particle assembly coordination number of 9.4 in clay loam and 4.6 in loamy sand which effected comparable quality change in the DEM, based on field test. The model of root for soil-sweep-root interaction was validated by a laboratory shear cut test. The simulation with the developed model showed that breakable roots have a notable influence on draught force, while the number of roots utilised was also an important parameter. (c) 2021 The Author(s). Published by Elsevier Ltd on behalf of IAgrE. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/ ).