Three dimensional finite element model of soil compaction caused by agricultural tire traffic

Most of the finite element models of soil compaction do not represent the tire, only the effect of a uniform ground stress is distributed on a soil area with a preset form. It constitutes an oversimplification of the problem and it would yield erroneous contact conditions, because the tire-soil contact stress distribution is the result of simultaneous tire and soil deformation. This research was carried out with the objective of developing a model, valid for soil compaction simulation caused by agricultural tire traffic that allows research factors that cause soil compaction of a Rhodic Ferralsol soil. The tire was developed as a unique solid layer, which represents its mean properties with a linear elastic constitutive model. Predictions of deflection and tire contact area in rigid surface were compared with experimental results and the tire model was validated. A three dimensional model of the soil was created and the soil properties were represented with an Extended Drucker Prager material model. ABAQUS/STANDARD 6.8-1 code was used to develop the tire-soil interaction model. A tire traffic experiment was carried out at a soil bin to two soil water conditions, tire inflation pressures and tire load. Triaxial and direct shear tests were used to obtain soil properties and constitutive parameters. Predictions were compared with experimental results to verify the validity of the model in each soil water content. Simulated and observed stresses after wheel traffic under different inflation pressures and tire loads agree well. The model predicts the effect of inflation pressures, ground pressure and tire load on the stresses on the contact and the soil profile, it can be used in both teaching and research. The model was used to predict the depth at which soil compaction was produced for each combination of tire inflation pressure and tire load, and the relationship between the tire inflation pressure, contact stress and tire load with soil compaction. The model showed that magnitudes of vertical stresses transmitted to soil are independent to water content and that more soil compaction in wet soils depends on the less yield stresses in those conditions. Besides, the good agreement of the model with experimental results demonstrates the validity of using the Extended Drucker Prager model to represent the mechanical response of the Rhodic Ferralsol soil.