Research On The Mechanism Of Subsoiling In Paddy Soil Using DEM

Rice wheat rotation system is one of the leading high yield cultivation pattern of the Yangtze River region,but the mode for annual dry wet cycles,rice season flooding and long-term shallow rotation generation of deep plowing turn caused soil hardening,low porosity,shallow topsoil is becoming a serious problem,severe restrictions on rice and wheat crops the high yield and quality improvement.In order to improve the structure of paddy soil,in recent years,people began to explore the possibility of the application of deep tillage technology in northern china.It is pointed out that the mechanism of soil tillage(especially subsoiling tillage)is very complex,and it is difficult to understand the behavior of deep soil by using traditional methods.In recent years,more emphasis has been laid on the analysis of soil mechanical tillage by means of discrete element numerical simulation.In this paper,the paddy soil as the research object,the discrete element method based on deep loosening soil disturbance process are analyzed,further combined with the field test of wet sticky rice soil mechanical subsoiling soil failure mechanism and mechanical behavior of subsoiling and soil structure effect,in order from the micro angle disturbance simulation process and crushing mechanism the realization of coordination and macro field test results,provide a reference for the South and the methodology of tillage machines research support.The main research contents and conclusions are as follows:The soil parameters of paddy soil were tested in a comprehensive way,and the differences of soil types and structure characteristics in paddy soil and dry land area were mastered.The test results show that the average moisture content of paddy soil in about 30%;changes curve of shear resistance of soil compaction characteristics and mechanical properties with soil depth analysis showed that the paddy soil at a depth of about 15 cm has obvious stratification characteristics.Based on the field test results,a discrete element subsoiling tillage model is established.It mainly includes the deep shovel,the virtual soil trough geometry model,the double layer discrete element soil model,and the key parameters of the soil particle contact model are calibrated.The final results for the 0-150mm model,soil 150-400mm to the bottom of the soil,soil and bottom soil adhesion critical stress were3 × 105Pa and 5 × 105Pa,finally get all parameters of simulation model design is shown in table 3-2.Based on the discrete element model,the mechanism of subsoiling tillage in paddy soil was analyzed.This paper includes the analysis of the micro process of soil disturbance,the disturbance of subsoiling soil,the analysis of soil micro displacement,and the optimization of the structure parameters of the deep loosening shovel.The results show that the tillage resistance increases with tillage depth,when the tillage depth is less than 200mm,increases slowly with increasing tillage resistance;tillage depth continues,tillage resistance increased sharply when the tillage depth is 300 mm when the level of tillage resistance and vertical tillage resistance reached the maximum,5.48kN and 2.56kN respectively.Soil disturbance and ridging height width with tillage depth increases first and then decreases in the tillage depth is 200mm maximum,166mm and 402mm respectively.On the other hand,the micro disturbance process of subsoiling soil is analyzed,further clarify the subsoiler and soil interaction mechanism,the sirmulation model of adhesive fracture angles of the deep loose disturbance boundary,soil crushing process.Based on the different positions of the deep loosening shovel structure,the four stages of the process of digging,lifting,shearing and falling are analyzed.The analysis of the displacement of the soil movement showed that the soil was larger in the tillage direction and vertical direction,and the lateral soil disturbance was not obvious.The tillage experiment was carried out,and the results of field experiment and simulation were compared and analyzed.The results showed that the average error of tillage resistance was 6.63%,the average error of soil disturbance ridge width was 4.39%,and the average error of ridge height was 19.22%.By using the discrete element EDEM software,the paper presents the index of“fracture coefficient”.In this study,when the tillage depth is within 200mm,the fracture coefficient is stable at about 30%,and the fracture coefficient increases to more than when the depth is greater than 200mm.Compared with the traditional field experiment,the soil fragmentation index is in the acceptable range both in the change tendency and the relative error.