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机械压实是造成土壤退化的重要原因之一,研究并预测土壤应力有助于科学规划田间机械使用,缓解压实问题。基于分析模型预测土壤应力的关键在于选择合适的集中系数。然而在已有的研究中集中系数取值混乱,导致该模型使用时存在很大争议,其原因在于对该参数随土壤环境的变化缺乏规律性认识。本文通过对集中系数表达式的进一步推导,在理论上提出了能够代表土壤环境对集中系数影响的无量纲参数σ_z/σ_0,定义为应力传递系数(STC)。基于水稻土和黄棕壤两种土壤,通过控制含水率和湿密度于室内重塑30种状态的土壤,在单轴压缩实验中运用土压力传感器测量计算应力传递系数,建立应力传递系数与土壤环境参数,如含水率、干密度和先期固结压力等之间的相关性分析。结果表明应力传递系数随土壤含水率的增大而增大,土壤初始干密度和先期固结压力与应力传递系数之间负相关性明显。根据所得应力传递系数计算相应土壤状态下的集中系数,其取值在1.20~12.39之间,与以往的研究结果相差不大,但包含了关于集中系数随土壤环境变化的具体信息。这意味着作为一个稳定可测的无量纲参数,应力传递系数为集中系数的计算提供了一个相对科学的方法,在定量描述土壤环境对集中系数影响的同时,完善了分析模型。
Mechanical compaction is one of the important causes of soil degradation. Studying and predicting soil stress helps to plan the mechanical use in the field and ease the compaction problem. The key to predicting soil stress based on the analytical model is to choose the appropriate concentration factor. However, in the existing research, the value of the concentration coefficient is confused, which leads to great controversy when using the model. The reason is that the parameter is lack of regular understanding with the change of the soil environment. In this paper, we derive the dimensionless parameter σ_z / σ_0, which can represent the influence of soil environment on the concentration coefficient, and define the stress transfer coefficient (STC) by further derivation of the expression of concentration coefficient. Based on soil of paddy soil and yellow brown soil, 30 kinds of soils were remodeled indoor by controlling water content and wet density. In uniaxial compression test, soil pressure sensor was used to calculate and calculate stress transfer coefficient, and the relationship between stress transfer coefficient and soil Environmental parameters such as moisture content, dry density and pre-consolidation pressure correlation analysis. The results show that the stress transfer coefficient increases with the increase of soil water content, and the negative correlation between initial dry density, pre-consolidation pressure and stress transfer coefficient is obvious. According to the obtained stress transfer coefficient, the concentration coefficient under the corresponding soil condition is calculated, which is between 1.20 and 12.39, which is not much different from the previous research results, but contains the specific information about the change of the concentration coefficient with the soil environment. This means that as a stable and measurable dimensionless parameter, the stress transfer coefficient provides a relatively scientific method for calculating the concentration factor, which improves the analysis model while quantitatively describing the influence of soil environment on the concentration factor.