小型拖拉机土壤压实的有限元预测

农业土壤的基本特征是松软和经常处于非饱和状态，土壤体积密度与含水率既是主要参数又是影响压实的重要因素，且在不断地变化。为了进行有效田间土壤压实管理，根据具体土壤特性，采用一个二维的模型，用有限元方法进行土壤压实预测。模型考虑了应力路径、初始土壤体积密度和含水率等，将土壤体积密度视为平均主应力和最大自然剪切应变的非线性函数，可预测小型拖拉机在非饱和土壤上通过时引起土壤体积密度的变化及应力分布情况等。在华北轻壤土的试验证明，模型具有良好的拟合效果。

Prediction of Soil Compaction by Small Tractor Using Finite Element Method

The main characteristics of agricultural soil are soft and unsaturated, the soil bulk density and moisture content are not only main parameters but also main factors influencing the soil compaction, and they are variable. In order to manage the soil effectively in the field, on the basis of particular soil type, a two-dimensional (2D) finite element model was developed as a tool that can be used to predict the soil compaction caused by small tractor. In the model, the soil compaction was expressed as a nonlinear function of both normal stress and maximum natural shearing strain. The initial values of the soil bulk density and the moisture content, and the stress path were considered in the model. The finite element model was verified with the field test data. The result showed that the soil bulk density and major principal stress could be predicted well in an initially loose soil profile of silty loam in north areas of China.