DEM simulation of stress transmission under agricultural traffic Part 1: Comparison with continuum model and parametric study
The discrete element method (DEM) is an appealing technique to study the effect of wheel loads and traction on the soil. Unlike in continuum-based soil mechanics, the soil is modelled as an assembly of particles, which move and interact with each other and transmit stress through force chains. In this study, the simulation of stress transmission under wheeling with the continuum method and with DEM was compared. Both methods showed a good agreement in the simulation of the vertical normal stress. The horizontal stresses were strongly different due to traction and draw-bar forces. Stresses in the DEM simulation were transmitted via a heterogeneous network of force chains: there was a coexistence of a distinct load-bearing and a dissipative force network in the shallow layers. Furthermore, the effect of the DEM material parameters (normal and shear stiffness and cohesion, and friction angle), wheel radius and traffic speed on the transmission of stress was evaluated. The normal and shear stiffness mainly influenced the depth of the stress transmission, and the friction angle influenced the horizontal stress transmission. The wheel radius influenced the stress distribution in the topsoil, but did not have a significant effect in deeper layers. Contrary to findings in literature on soil compaction, the increased traffic velocity caused higher stresses. DEM allows to simulate the geomechanical process of soil compaction and can give more insight in the role of heterogeneous stress transmission.
Keywords: Soil compaction, Force chain, Traction, Söhne,