Prediction model for non-inversion soil tillage implemented on discrete element method

• Water content and dry bulk density as modifier of clay soil mechanical properties.
• Statistical equations and discrete element model reproduce soil–tool interaction.
• Soil physical condition and tool geometry modify the draft forces requirement.
• Soil behavior and tool draft force agree with result from soil-bin experiment.

In the present study the discrete element method is used for predicting forces reactions and soil behavior during non-inversion tillage. The numerical model at particle level works with a force system integrated by normal, shear, cohesion and friction forces. Macro parameters are defined as the soil mechanical properties obtained by soil mechanical tests. The behavior of soil–soil and soil–metal interface at different dry bulk densities and gravimetric water contents were determined by modified direct shear box and triaxial compression tests. A set of statistical regression equations feasible to estimate the macro values of Young’s modulus, shear strength, soil friction and soil cohesion were obtained. The relationship between macro and micro behavior of soil friction was investigated by means of the simulation of direct shear tests. The discrete soil model was used to simulate soil tillage at conditions called hard-dry, soft-wet and friable state. To calibrate the model, a soil-bin was filled with the soil previously characterized and equipped with a tool similar to the one used for the simulation. A National Instrument Data Logger system was configured aimed at measuring vertical and horizontal reaction forces. The comparison between draft forces from simulation and soil-bin tests showed a small under-predicted behavior of the model for loose soil with high moisture; this behavior was fixed toward compacted and dry soil conditions. Para-plough and moldboard were the tools used for non-inversion tillage simulation at different physical states of the soil. The result shows the pattern of movement and force distribution related with the geometry of the tool.