DEM simulation of subsoiling for soil disturbance as affected by soil layering and working speed

Abstract

Although the discrete element method (DEM) has been used to simulate soil-subsoiler interactions, the degree of soil heterogeneity along the depth profile has not been well documented. Models of a layered soil structure were developed using the DEM, and they were a heterogeneous soil model (HeS Model) with seven layers, a semi-heterogeneous soil model (SHeS Model) with three layers, and a homogeneous soil model (HoS Model) with one layer. The models simulated the soil dynamic behavior resulting from a subsoiler travelling at speeds from 2 to 6 km h−1. Simulations were compared with field measurements. Results showed that soil particles flow in front of the subsoiler formed three distinguished zones: “pushing”, “rising”, and “passive” zones, with the “pushing” zone having the highest particle velocities. Compared with the measurements, the overall relative errors of the simulated soil disturbance widths (W) within the range of working speed from 2 to 6 km h−1 were below 20 % for all three models. Whereas the overall relative errors of the simulated soil surface flatness (F) were larger than 20 % for all three models. These suggest that all three models are suitable for predicting W, but not for predicting F, if a 20 % relative error was used as the judging criterion. The overall relative errors of the simulated elevated soil area (A) were 11.1 %, 18.8 %, and 25.7 % for the HeS, SHeS, and HoS Models, respectively, which suggest that HeS Model had the highest accuracy in predicting A. This study provides critical information for determining the degree of soil heterogeneity in simulations of the dynamics of soil-subsoiler interaction.