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Numerical Modeling of Large-Scale Pavement Experiments Using Fast Lagrangian Analysis of Continua (FLAC3D)
AuthorEl Sebaaly, Michel
AdvisorSiddharthan, Rajaratnam V.
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The movement of superheavy loads (SHLs) on the pavement structure can cause severe damage to the infrastructure if the pavement was not designed to sustain such loads. Researchers at University of Nevada, Reno (UNR) conducted full large-scale pavement experiments with various pavement characteristics (layer configurations and loadings) to simulate field conditions and address the problem.In this thesis, pavement loading responses of five different large-scale pavement experiments were evaluated using a numerical method and were compared to the responses measured by the experimental program undertaken by UNR researchers. The first experiment was on a subgrade layer. A crushed aggregate base was added on top of the subgrade in experiment No.2. The subsequent experiments consisted of a full three layers pavement structure whereas experiment No.4 simulated a full pavement structure with a sloped shoulder. The final experiment was on a full pavement structure with two buried utilities located in the subgrade layer. The utilities consisted of flexible and rigid pipes. The numerical approach was undertaken using Fast Lagrangian Analysis of Continua in Three Dimension (FLAC3D) along with FISH functions, which use built-in scripting language that give the user powerful control over many aspects of program operation. Special considerations had to be given to generate mesh configurations for model experiments No.3 and No.4 as they included sloping pavement shoulder and buried utilities. In this study, the top two layers were modeled using the built-in isotropic elasticity model (constant modulus), but the bottom layer (subgrade) was modeled using the FISH function to characterize its non-linear stress-dependent behavior using an iterative solution approach. The focus in predicted results was given to stresses, in particular vertical stresses at various locations within the pavement. The main reasons for this focus are: (1) availability of recorded data from TEPCs; and (2) the importance of vertical stresses relative to pavement performance predictions. Although many factors affect the results generated by FLAC3D when modeling pavement structures, the vertical stresses predicted present reliable results when compared to the measured results. This means that FLAC3D can be used for multi-layer pavement investigations when complex loading (normal and shear interface stresses) and layer profiles (sloping and existence of water table, etc.) are present. It may be important to model the vehicle-pavement interaction as a dynamic moving load and such loading scenario can be undertaken using dynamic loading options available in FLAC3D.