DEM simulation of plate sinkage in soil: Calibration and experimental validation

Abstract

Due to granular nature of the soil media, 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. In terramechanics, plate sinkage test (PST) is widely applied as a conceptual method for simulation of the soil-wheel interaction in order to characterize the soil behavior during compaction and estimate the vehicle rolling resistance. This study was therefore aimed at development and calibration of a DEM model for PST using the hysteretic spring-linear cohesion (HS-LC) contact model for agricultural soils. It was hypothesized that confined compression (CCT) and direct shear tests (DST) could be assigned as appropriate tests for parameters’ calibration of HS-LC contact model of PST. The cohesion and internal coefficient of friction were directly obtained from experimental DST whereas the other parameters were estimated by matching the stress vs. sinkage of experimental and simulated CCT. Experimental tests were carried out for a clay loam soil at two water contents of 11 and 16 percent each at two dry bulk densities of 1000 and 1150 kg m−3. DEM-simulated CCT indicated to be more significantly affected by particle yield strength which was calibrated by comparing the stress vs. sinkage of experimental and simulated CCT. Calibration of DEM parameters with CCT-DST resulted in remarkable underestimation of stress vs. sinkage for PST. A satisfactory agreement was found for evaluated soils between simulated and measured stress vs. sinkage for PST when the experimental cohesion and internal coefficient of friction were increased with the factors of 11 and 4, respectively. Large difference between the particle size of actual soil and DEM-simulated particles might be the reason of this mismatch which needs further studies aimed at scaling the DEM parameters with respect to particle size.