Calibration of the Kneading contact model by a simplified infiltration test for modeling rotary-tillage mixes of liquid amendments and soils

Liquid soil amendments could improve the characteristics of soils and positively affect crop yields by mixing them with soils evenly. However, the lack of a scientific approach to model the mix by the discrete element method (DEM) limited the development of the study of the mixing mechanism, where a reliable method for calibrating the DEM parameters was critical. To solve this, this study developed an amendment infiltration test (AIT) to calibrate DEM parameters by using the Kneading contact model. The relationships between the DEM parameters and the AIT results were evaluated, and the DEM parameters were calibrated. Then a rotary tillage with mixing liquid amendment test (RTMLAT) was used to verify the reliability of the calibrated parameters, where the liquid contents at 50 mm and 100 mm depths were used to evaluate differences between experimental RTMLAT and simulated RTMLAT. It was shown that the maximum liquid content of the measured layer in the AIT was linearly correlated with the parameter of the minimum liquid content gradient (R2 = 0.9987), and the maximum slope for 10 consecutive seconds was also linearly correlated with the parameter of the liquid conductivity (R2 = 0.9989). DEM parameters of the minimum liquid content gradient and the liquid conductivity were calibrated to 0.678 % and 30.33 s, respectively. The verification results showed that the trend of the liquid content distributions simulated by RTMLAT was the same as in the experiment. The differences between simulated and measured average liquid content in the 50 mm and 100 mm depths were 1.08 % and 0.54 %, respectively. These were shown that the Kneading model parameters calibrated by the AIT could give reliable results in RTMLAT. A DEM calibration approach for modeling the mixes of liquid amendments and soils was developed. It would provide a scientific approach to model the DEM solid–liquid mixing.