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

土壤-工具-残留物的相互作用是许多农业田间作业的中心。土壤-机具-残茬相互作用也是土壤动力学在农业工程中的基本内容之一。在田间作业中，耕作工具（例如犁、凿子、清扫机等）用于苗床准备的松土器或种子开沟器（如锄头、圆盘、铲子等）开放的土壤用于播种。这些耕作工具和播种开启器的总称是“土壤接合工具”。由于农田保留了来自先前作物的或多或少的作物残留物，因此土壤接合工具在田间操作期间与土壤和作物残留物两者相互作用。土壤-工具-残留物是一个复杂的系统，因为土壤由离散颗粒组成，这些颗粒具有随机性、非均匀性，并表现出复杂的非线性行为。这样的系统不能使用传统的分析或数值方法建模。本文提出的最新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残留物颗粒的存在。在拟议的研究计划中，一个新的，创新的数值方法-离散元法（DEM）-将用于开发通用的土壤工具残留物相互作用模型。在该模型中，基本土壤颗粒将由各种尺寸的球形颗粒表示。颗粒本构律将以这样一种方式定义，即基本颗粒可以形成聚集体，并具有摩擦、内聚、粘性和变形行为，就像真实的农业土壤（第一次创新）一样。将使用接触的土壤颗粒之间的键来描述内聚行为。键将土壤颗粒连接在一起，形成土壤聚集体，并且键在土壤接合工具的冲击下是可断裂的。该模型必须包括颗粒和粘结剂的微观性质（如颗粒弹性模量、粘结强度和颗粒摩擦系数）。这些微观特性将被定义为与颗粒尺寸无关，因此它们是通用的（第二创新）。由于DEM颗粒的微观性质是不可测量的，由于其微观尺度，将开发的方法来校准的微观性质。将使用基础土壤力学测试进行校准，以便校准的微观特性具有通用性，独立于土壤接合工具（第三次创新）。在该模型中，残留物颗粒将由一簇基本球形颗粒表示，这些颗粒以反映真实的作物残留物形状的方式排列。不同大小的残留物簇将被整合到土壤颗粒中，形成一个由离散土壤和残留物颗粒混合而成的非均匀模型域（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。农业土壤动力学行为的DEM模拟是一个新兴的领域。通用土壤-工具-残留物模型的开发将标志着土壤动力学领域的一个潜在突破，因为该模型可以用于模拟任何土壤条件下任何土壤接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，这些工具消耗最小的拖拉机功率，并为作物生长创造最佳的土壤条件。其结果也将有助于作物残留物管理，以促进可持续农业。

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.