Development of universal soil-tool-residue interaction models using the discrete element method (DEM)

土壤-工具-残留物相互作用是许多农业田间作业的中心。土壤-工具-残渣相互作用也是农业工程中土壤动力学研究的基本内容之一。在田间作业中，耕作工具(如犁、凿子、扫地等)为准备苗床或开种器(如锄头、圆盘、铲子等)松土。开阔的土壤，便于播种。这些耕作工具和播种器的总称是“土壤啮合工具”。由于农田或多或少保留了以前作物的残留物，土壤接触工具在田间作业过程中与土壤和作物残留物相互作用。土壤-工具-残留物是一个复杂的系统，因为土壤是由离散的颗粒组成的矩阵，这些颗粒具有随机性、异质性，并表现出复杂的非线性行为。这样的系统不能用传统的分析或数值方法来建模。这里提出的最先进的研究将开发一个通用的土壤-工具-残留物相互作用模型，该模型可以解决土壤的复杂性质和农业领域中残留物颗粒的存在。在拟议的研究计划中，将使用一种新的、创新的数值方法-离散单元法(DEM)-来建立通用的土-工具-残留物相互作用模型。在该模型中，基本土壤颗粒将由不同大小的球形颗粒来表示。颗粒本构定律将以这样的方式定义，即基本颗粒可以形成集合体，并具有与真实农业土壤一样的摩擦、粘性、粘性和可变形行为(第一次创新)。粘聚力行为将使用接触的土壤颗粒之间的结合来描述。粘结剂将土壤颗粒连接在一起，形成土壤团聚体，在土壤接合工具的影响下，粘结剂很容易断裂。该模型必须包括颗粒和粘结剂的微观属性(如颗粒弹性模数、粘结剂强度和颗粒摩擦系数)。这些微观性质将被定义为独立于颗粒大小，因此它们是通用的(第二次创新)。由于DEM颗粒的微观尺度是不可测量的，因此将开发标定DEM颗粒微观特性的方法。将使用基本的土壤力学测试进行校准，因此校准的微观性质是通用的，独立于土壤啮合工具(第三次创新)。在该模型中，残留物颗粒将由一群基本的球形颗粒表示，其排列方式反映了真实作物残留物的形状。不同大小的残留物集群将被整合到土壤颗粒中，形成一个由离散的土壤和残留物颗粒混合而成的异质模型域(第四次创新)。通用模型将能够预测土壤微观动力学(例如，每个土壤颗粒的力和位移)。模型将使用实验室和现场数据进行验证。农业土壤动态行为的DEM模拟是一个新兴的领域。即将开发的通用土壤-工具-残留物模型将标志着土壤动力学领域的一项潜在突破，因为该模型可以用于模拟任何土壤条件下任何土壤啮合工具的微观土壤动力学行为。模拟结果将导致新的高性能耕作和播种工具的出现，这些工具消耗的拖拉机功率最小，并为作物生长创造最佳的土壤条件。研究结果还将有助于可持续农业的作物残留物管理。

Soil-tool-residue interaction is at the centre of many agricultural field operations. Soil-tool-residue interaction is also one of the fundamental aspects of soil dynamics in agricultural engineering. In a field operation, tillage tools (e.g. plows, chisels, sweeps, etc.) loosen soil for seedbed preparation, or seed openers (e.g. hoes, discs, shovels, etc.) open soil for seed placement. A general term for these tillage tools and seeding openers is "soil engaging tool". As agricultural fields retain more or less crop residue from previous crops, soil engaging tools interact with both soil and crop residue during field operations. Soil-tool-residue is a complex system, since soil consists of a matrix of discrete particles that are of random, heterogeneous nature, and exhibit sophisticated non-linear behaviours. Such a system cannot be modelled using traditional analytical or numerical methods. THE STATE-OF-THE-ART RESEARCH proposed here will develop a universal model of soil-tool-residue interaction, which can address the complex nature of soil and the existence of residue particles in agricultural fields. In the proposed research program, A NEW, INNOVATIVE NUMERICAL METHOD - DISCRETE ELEMENT METHOD (DEM) - will be used to develop the universal soil-tool-residue interaction model. In the model, basic soil particles will be represented by spherical particles of various sizes. The particle constitutive laws will be defined in such a way that basic particles can form aggregates and have frictional, cohesive, viscous, and deformable behaviours like real agricultural soil (1st INNOVATION). The cohesive behaviour will be described using bonds between soil particles that are in contact. Bonds connect soil particles together, forming soil aggregates, and bonds are breakable under the impact of soil engaging tools. The model must include the microproperties of particles and bonds (such as particle modulus of elasticity, strength of bond, and particle friction coefficient). These microproperties will be defined to be independent of particle sizes, so that they are universal (2nd INNOVATION). As the DEM particle microproperties are not measurable owing to their micro-scales, methods will be developed to calibrate the microproperties. Calibration will be performed using fundamental soil mechanical tests, so that the calibrated microproperties are universal, independent of soil engaging tool (3rd INNOVATION). In the model, a residue particle will be represented by a cluster of basic spherical particles arranged in a way that reflects the shapes of real crop residues. Different sizes of residue clusters will be integrated into soil particles, forming a heterogeneous model domain with a mixture of discrete soil and residue particles (4th INNOVATION). The universal model will be able to predict soil micro dynamics (e.g. forces and displacements of each individual soil particle). Models will be validated using laboratory and field data. DEM modeling of dynamic behaviours of agricultural soil is an emerging field. The universal soil-tool-residue model to be developed will mark a potential BREAKTHROUGH in the area of soil dynamics, in that the model can be used to simulate the micro soil dynamic behaviours for any soil engaging tool, in any soil condition. The simulation results will lead to the emergence of new high performance tillage and seeding tools that consume minimal tractor power and create optimal soil conditions for crop growth. The outcome will be also useful in crop residue management for sustainable agriculture.