DETERMINATION OF PHYSICAL PROPERTY PARAMETERS OF CLAYEY SOIL IN RICE STRAW FIELDS AND CALIBRATION OF DISCRETE ELEMENT SIMULATION PARAMETERS

Soils in China's Yangtze River Basin are heavy and cohesive. During simulation studies of rotary tillage preparation, obtaining accurate soil fragmentation patterns has been challenging due to the lack of precise soil discrete element parameters. This study calibrated the physical and contact parameters of heavy clay soils using the EDEM discrete element method. Soil density, shear modulus, Poisson's ratio, collision recovery coefficient, static friction coefficient, and rolling friction coefficient between soil-soil and soil-tiller components were experimentally determined. Soil penetration tests were conducted using the Hertz-Mindlin with JKR contact model in EDEM software. A Plackett-Burman design identified four parameters significantly influencing soil penetration stiffness: soil-soil collision recovery coefficient, soil-soil static friction coefficient, JKR surface energy, and soil-soil rolling friction coefficient. Building upon this, a second-order regression model linking soil firmness to key parameters was established via Box-Behnken experiments. An optimization algorithm was then employed to determine optimal parameter values, yielding the following combination: soil-soil static friction coefficient 0.441, soil-soil collision recovery coefficient 0.537, and JKR surface energy 9.551 J/m². Validation results demonstrated that under optimal parameters, the simulation error of soil stiffness compared to experimental data was only 3.0%, confirming the accuracy of the calibrated parameters.