Discrete Element Simulations And Experiments On The Influence Of Stratified Subsoiling On Soil Disturbance

The layered subsoiling can promote the maturation of deep soil,improve the water-holding capacity of soil by adjusting the soil water,fertilizer and gas.The longitudinal and vertical distances of the current layered subsoiler were mainly selected in accordance with experience and there is still no standard determination method.Using high-speed photography technology,discrete element method(DEM),digital soil-bin tests and response surface method(RSM),the influence of key structural parameters of layered subsoiler on soil microscopic and macroscopic disturbance behaviors were studied.This study provided implication for decision of the structural parameters of layered subsoiler.(1)Determination of soil parameter and construction of model.To establish an accurate discrete element model,soil quality,density,water content,compactness and shear strength were determined by sieving method,ring knife method,drying method and fast shearing method.DEM models with layered subsoiler with different structural parameters were developed.(2)The influence of the longitudinal distance of the layered subsoiler on soil disturbance behaviors were evaluated and validated using the DEM simulations and digitalized soil-bin tests.The results showed that when the longitudinal distance of the layered subsoiler increases,the soil bulkiness and soil disturbance coefficient initially increased and then decreased.The longitudinal distance of the layered subsoiler directly affects the displacements in different directions of soil at different depths during subsoiling.The average errors between simulated and experimental soil bulkiness,soil disturbance coefficient,draught force and specific draught force(SDF)were 12.41%,13.61%,13.84% and 3.34%,respectively;this indicates that DEM simulations can accurately simulate the disturbance process of the layered subsoiler.(3)The influence of vertical distance of the layered subsoiler on macro and micro soil disturbance behaviors was studied.The results showed that the vertical distance has an important impact on soil disturbance.It directly affected the displacements in different directions of soil at different depths during tillage;the average errors between simulated and experimental soil bulkiness,soil disturbance coefficient,draught force and specific draught force(SDF)were 11.04%,7.19%,2.96%,and 13.31%,respectively,and the accuracy of the DEM model is reasonably high.(4)Optimization of structural parameters of layered subsoiler.The effects of structural parameters of layered subsoiler on the SDF were studied by DEM simulations and quadratic orthogonal tests.The regression equation between the structural parameters of layered subsoiler and the SDF was established.The vertical distance affected the SDF the most,followed by longitudinal distance,and working depth of the deeper subsoiler.The parameters of the layered subsoiler were optimized using the Design-Expert software.The optimal parameters of the layered subsoiler were 117 mm,352 mm and 300 mm,for the vertical distance,longitudinal distance and the working depth of the deeper subsoiler.The average relative error between the soil-bin test results and the simulated results was 13.18%,which indicates that the DEM is feasible in studying the layered subsoiler.The study can have implications for the design and optimization of the layered subsoiler.