Simulations of micro-dynamics of soil, tool, and crop residue using the discrete element method (DEM)

点击翻译按钮获取中文摘要

Soil-tool-residue interaction is not only at the centre of many agricultural field operations, but also one of the fundamental aspects of soil dynamics in agricultural engineering. In modern conservation agriculture systems, at least 30% of an agricultural field is covered by crop residue from the previous crops. Thus, soil engaging tools (e.g. plows, discs, sweeps, etc.) interact with both soil and crop residue during a field operation, such as tillage and seeding. Soil-tool-residue is a complex system, since soil consists of a matrix of discrete particles that are of random, heterogeneous nature, and exhibit sophisticated non-linear behaviours. Such a system cannot be modelled using traditional analytical or numerical methods. In the proposed research program, an innovative numerical method, the discrete element method (DEM), will be used to develop universal soil-tool-residue interaction models. In the model, multiple spheres of various sizes and shapes will represent a soil particle. The particle constitutive laws will be defined in such a way that basic particles can form aggregates and have frictional, cohesive, viscous, and deformable behaviours like real agricultural soil (NOVELTY 1). The cohesive behaviour will be described using bonds between soil particles which are in contact. Bonds are breakable under the impact of soil engaging tools. Model microproperties (such as particle modulus of elasticity, strength of bond, and particle friction coefficient) will be defined to be independent of particle sizes, so that they are universal (NOVELTY 2). As the DEM particle microproperties are not measurable, methods will be developed to calibrate the microproperties. Calibrations will be performed using fundamental soil mechanical tests, so that the calibrated microproperties are universal and independent of the soil engaging tool (NOVELTY 3). In the model, a residue particle will be represented by a cluster of basic spheres arranged in a way to reflect the shapes of real crop residues. Residue clusters will be integrated into soil particles, forming a heterogeneous model domain with a mixture of discrete soil and residue particles (NOVELTY 4). The universal models will be able to predict soil micro dynamics: including forces and displacements of each of individual soil and residue particles, stress distribution in particle assembly, and pressure distribution on the surfaces of soil engaging tools (NOVELTY 5). Models will be validated using laboratory and field data. DEM modeling of dynamic behaviours of agricultural soil is an emerging field. Understanding of micro dynamic attributes of soil, residue, and tools will mark a potential breakthrough in the area of soil dynamics. This will lead to the emergence of new high performance soil engaging tools which consume minimum tractor power and create optimal soil and residue conditions for food production in sustainable agriculture.