Modelagem da compactação por tráfego agrícola após o preparo do solo em tabuleiro costeiro

Abstract

The passage of traffic after conventional soil preparation causes negative effects throughout the sugarcane production cycle. To understand this process of transmission of tensions from vehicles to the ground and its consequences on soil compaction, simulation models are used. Among them we have the pseudo-analytical models, derived from Fröhlich and Boussinesq, and the numerical models such as the finite element method (FEM). The aim of this study was to i) perform pseudo-analytical analyzes using different Fröhlich concentration factors (3, 4, 5 or 6) and compare the vertical stress results with two-dimensional (2D) and three-dimensional (3D) FEM models; and ii) simulate a truck and a tractor by the FEM (3D) and analyze the soil properties that change after the vehicles pass. In the first chapter, for the FEM simulations, all the parameters required by the Modified Cam Clay model were determined and the geometry of the soil profile was generated, with the stratification of five types of materials in a finite element mesh generator. For the pseudo-analytical model, the Soilflex model was used, in both tire/ground contact areas were simulated by the super-ellipse model. Results revealed that 3D numerical and pseudo-analytical models showed similarities to each other for vertical stress propagation. The 2D plane strain analysis overestimated the stress propagation, inducing the overlapping of bulbs between tires of the same axle, concentrating and propagating the vertical stress in soil depths far beyond what was observed for the others. The results recommend assigning a concentration factor of 3 for pseudo-analytical simulations. For the second chapter, the passage of a tractor and a sugarcane truck was simulated in a soil, after conventional preparation. With the parameters required by the Modified Cam Clay model, the geometry of the soil profile was generated, similar to the first chapter. The tractor applied the lowest vertical stresses in the tire-soil interaction and along the profile, while the truck tires reached stresses of 750 and 880 kPa on the soil surface, corresponding to the front and rear axles, respectively. The highest preconsolidation stress obtained after vehicle simulation was found in truck traffic, exclusively in the first layer (0.0-0.20). Below the wheels of all vehicles there was a reduction in porosity.