Análise da compactação do solo sob tráfego de máquinas na colheita da cana-de-açúcar através do método dos elementos finitos

Abstract

The machine-soil interaction study is crucial due to the compaction promoted by them mainly in semi-mechanized system. Thus, this study aims to analyze the behavior of the soil stress-strain in different layers in an Ultisol during the sugarcane harvest through numerical simulation by the Finite Element Method. Three sites, randomly selected in the crop line with layers from 0.2 m up to 1 m depth were used to perform the Visual Evaluation of Soil Structure (VESS), the soil penetration resistance, disturbed and undisturbed samples were collected for physical characterization analysis and several mechanical tests equilibrated in a water content corresponding to field capacity. All the parameters required by the Modified Cam-Clay elastoplastic model were determined through laboratory analysis. A mesh with a geometry of 9 x 4 m, which characterized the soil profile, was generated with the stratification of five types of materials in a Finite Element grid software. The distributed stresses of the different agricultural vehicles (tractor, truck and trailer) were calculated and applied, which were simulated through the Finite Element Method (FEM) in the numerical software CODE_BRIGHT. Pre-harvest parameters, such as pre-consolidation stress, soil penetration resistance (PR), dry bulk density (BD), aggregates, organic carbon and visual analysis were subjected to a multivariate analysis of variance at 5% probability, with canonical discriminant analyze. It was found that the trailer presented a greater propagation of the vertical stress, reaching up to 4 m of depth and 200 kPa at 1 m of depth. Under the wheels, as well as the tire-soil contact values of 880 kPa and 1 m depth were reached. There was an increase of the pre-consolidation stress and reduction of porosity along the profile, especially in the first layer. There was a canonical correlation between BD, PR, lower aggregate diameter, pre-consolidation stress and visual soil analysis scores. The layer 0-0.2 m presented higher concentration of organic carbon and higher percentage of aggregate diameter (> 2 mm). The 0.2-0.4 m layer presented higher BD, PR, VESS and percentage of aggregates of <0.25 mm.