Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Agricultural and Biosystems Engineering

First Advisor

Don C. Erbach


Prediction of soil compaction of agricultural soils is very difficult due to the variability of these soils. A numerical method, such as the finite element method, may be the only technique that can take into consideration their variability and be used to predict this quantity. Therefore, a finite element program has been developed that takes into consideration the nonlinear constitutive relationship of agricultural soils. This nonlinear relationship was taken from research at the National Soil Dynamics Laboratory (NSDL) and Auburn University in Auburn, Alabama where a compaction model has been developed. This compaction model was used to predict values of linear elastic parameters, Young's modulus and Poisson's ratio, that were used in the finite element model and varied for each element. An incremental loading technique was used by this model to gradually load the soil medium so that these quantities could be varied numerous times over the loading period. An experiment was performed in a soil bin at the NSDL to obtain stress values in the soil to check the finite element model's predictive accuracy. Three of four loading configurations that were tested at the NSDL were accurately modeled. Overall results were promising from this program and it can be used to reasonably predict the stress state and compaction beneath an axisymmetric device such as a tire.



Digital Repository @ Iowa State University,

Copyright Owner

Randy Lee Raper



Proquest ID


File Format


File Size

249 pages