湿粘水稻土深松过程离散元分析

DEM Analysis of Subsoiling Process in Wet Clayey Paddy Soil

湿粘水稻土的深耕松对作业机具设计与作业参数的要求不同于旱作制,为探究水稻土条件下土壤深松扰动过程及其内在相互作用机理,本文结合田间实测土壤物理参数,借助离散元EDEM软件,建立适用于粘性水稻土的深松耕作离散元模型。利用粘性水稻土模型对水稻土的机械深松耕作过程进行离散元模拟仿真,并结合田间试验结果对机具耕作阻力、土壤宏观扰动进行对比验证,进一步从仿真的角度揭示深松土壤扰动的微观过程、土壤失效破碎的微观机理。结果表明,该模型下深松耕作阻力平均误差为6.63%,土壤扰动的起垄宽度平均误差为4.39%,起垄高度平均误差为19.22%;DEM仿真对土壤的微观扰动过程分析进一步论证了宏观试验测试结果及假说的正确,并且能够从土颗粒接触力学层面表达土壤扰动的边界生成、土体内部破碎等过程;结合DEM仿真角度提出的反映土体破碎程度指标——断裂系数,与传统试验的指标参数碎土系数对比两者误差为3.46%,该指标更有利于对土壤破碎过程微观机理的表达。

Tool design and working parameters for subsoiling in wet clayey paddy soil are different from those for dry land cropping system. Investigation on the subsoiling process and the governing mechanisms requires detailed description on the underlying influential factors. Field soil parameters were used as a reference to construct a DEM model for subsoiling which was suitable for wet clayey soil analysis and performed in a EDEM software. The proposed DEM model of clayey paddy soil was then implemented to simulate a subsoiling process, in which directly measured draft and macroscopic disturbance of field soil was compared. Microscopic process and mechanisms of soil fragmentation were assessed with simulated stages. Results showed that simulation error with the proposed DEM model was less than 6.63%. Mean error of the resulted micro-relief was 4.39%. Mean error of elevated ridge was 19.22%. The measured results from microscopic approach were re-evaluated and the correctness of related assumptions from microscopic approach was confirmed by DEM results, soil failure boundary evolution and soil failure with particle contacting models were depicted. A soil fragmentation index was proposed for describing soil fragmentation behavior from DEM perspectives. The error of fragmentation index with respect to measured soil fragmentation parameter was less than 3.46% , affirming that the proposed parameter was a suitable tool for microscopic description of soil failure imposed by subsoiling. This research provides a powerful technical basis for the interaction mechanism between soil and soil, and lays a theoretical foundation for the optimization design of the soil contact parts.