Simulation of plate sinkage in soil using discrete element modelling: Calibration of model parameters and experimental validation

Discrete element method (DEM) has presented promising advantages in simulation of soil-machine/tool interaction. To develop reliable DEM simulations, selection and parametrization of a suitable contact model is crucial. The plate sinkage test is widely applied to characterize the soil behavior during compaction. This study aimed at setting up a DEM model for plate sinkage test using the hysteretic spring-linear cohesion contact model to (i) find the key parameters of the model which need to be calibrated and (ii) develop a calibration method for DEM parameters of the model for varying soil water content and bulk density of a cohesive soil. It was tested whether confined compression tests in combination with direct shear tests could be used to calibrate DEM parameters of the contact model. Soil cohesion and internal coefficient of friction were directly obtained and used from experimental direct shear test whereas particle yield strength was estimated by matching the stress-sinkage relationship of experimental and DEM-simulated confined compression tests. A clay loam soil at two water contents (11 and 16 %) and two dry bulk densities (1000 and 1150 kg m(-3)) was used to test the calibration method. Simulations using the parameterization obtained from the combination of confined compression and direct shear tests resulted in remarkable underestimation of plate sinkage. A satisfactory agreement with measurements was only found when the simulated cohesion and internal coefficient of friction were several times higher than measured. The factors were indicated to be constant with changes in soil water content and bulk density. A strong correlation was found between the particle yield strength and precompression stress estimated from confined compression tests. Using the factors obtained for increasing the cohesion and internal coefficient of friction and estimation of particle yield strength from precompression stress, a viable method for calibration of plate sinkage test could be proposed.