Modeling of Soil Sinkage by Multiple Loadings Using Finite Element Method

As the agricultural soil is exposed to multiple loadings of the same magnitude in this situation, it is valuable to predict soil sinkage by multiple loadings so as to utilize the tractor power effectively with minimum compaction effects. For this purpose, the finite element method (FEM) was used to predict soil sinkage by multiple loadings (ten loadings) of a rectangular plate and a two-dimensional FEM program entitled PRESSINK was modified and employed to perform required numerical calculations. The agricultural soil was considered as an elastoplastic material and the Drucker-Prager elastoplastic material model was adopted with the flow rule of associated plasticity. Also, to deal with material non-linearity, incremental method was adopted and to allow for the geometric non-linearity, the total Lagrangian formulation was used. The FEM analysis was finally verified through laboratory test. Results of the laboratory test proved that the FEM is a relatively accurate and powerful technique to predict soil sinkage by multiple loadings. Results of the study also indicated that the number of loadings noticeably affected soil sinkage. Moreover, the first three loadings caused critical soil sinkage and the amount of soil sinkage owing to the first three loadings was about 89% and 82% of the total soil sinkage based on the FEM analysis and laboratory test results, respectively.