Finite Element Simulation of Structural Performance on Flexible Pavements with Stabilized Base/Treated Subbase Materials under Accelerated Loading

1. Report No. FHWA/LA.10/452 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle Finite Element Simulation of Structural Performance on Flexible Pavements with Stabilized Base/Treated Subbase Materials under Accelerated Loading 5. Report Date December 2011 6. Performing Organization Code 7. Author(s) Zhong Wu, Ph.D., P.E., Xingwei Chen, Ph.D., and Xiaoming Yang 8. Performing Organization Report No. 9. Performing Organization Name and Address Louisiana Transportation Research Center 4101 Gourrier Avenue Baton Rouge, LA 70808 10. Work Unit No. 11. Contract or Grant No. LTRC Project Number: 07-1P State Project Number: 736-99-1405 12. Sponsoring Agency Name and Address Louisiana Transportation Research Center 4101 Gourrier Avenue Baton Rouge, LA 70808 13. Type of Report and Period Covered Final Report (November 2006-April 2010 ) 14. Sponsoring Agency Code 15. Supplementary Notes Conducted in Cooperation with the U.S. Department of Transportation, Federal Highway Administration 16. Abstract Accelerated pavement testing (APT) has been increasingly used by state highway agencies in recent years for evaluating pavement structures and/or materials. However, running an APT experiment is expensive. It requires costly accelerated loading devices and constructing full-scale pavement structures. Since pavement structures can have numerous combinations of pavement layer thicknesses, material types, and mixture designs, it is obviously impractical to test all potential pavement structures under APT. In order to maximize the benefits from an accelerated pavement testing (APT) study and utilize the APT results in the evaluation of other similar pavements with different structural configurations, a computer simulation of APT tests is essential. The objective of the research is to develop a finite element (FE) model(s) to simulate pavement structural performance of stabilized base and treated subbase materials under accelerated loading so that the performance of pavement structures with other stabilized base and subbase materials can be predicted without running APT tests. A permanent deformation (P-D) material model was proposed in this study to simulate the permanent deformation behavior of pavement base and subgrade materials under repeated loading. This model was modified from a conventional elastoplastic model with a linear strain hardening. All model parameters can be obtained from a laboratory P-D test. A P-D test data analysis spreadsheet by Excel Macro was developed to obtain parameters for the proposed P-D model. The P-D material model was implemented into a commercial FE program, ABAQUS through a user-defined UMAT subroutine. The P-D model was verified by simulating laboratory P-D tests for eight pavement base and subbase/subgrade materials. In addition, a sensitivity analysis was conducted to evaluate the effect of the material model parameters, pavement structures, and load configurations on the permanent deformation of pavement structures. The sensitivity analysis indicated that the proposed P-D model could effectively be used to predict the permanent deformation for different pavement structures. Three FE models for APT were preliminarily developed to investigate the dimensionality effect: a 3-D model with a moving load, a 3-D model with a repeated load, and an axisymmetric model. Considering the computational efficiency, the axisymmetric model was finally selected in this study. Six APT tests were simulated to calibrate the FE model. In the FE analysis, the load wander effect and the temperature change in pavement was considered. The calculated permanent deformations were in a reasonably good agreement with the field measurements with an average shift factor of 1.13. The FE model and the calibrated shift factor were also used to simulate pavement structures with other base/subbase materials. The predicted results showed that the performance of 2.6 percent lime/6 percent fly ash treated subbase was similar to that of 3.5 percent cement treated subbase. The analysis also showed that the lime/fly ash treated soil could be a viable alternative to the cement treated soil. In addition, the developed FE model was used to predict the permanent deformation of two low-volume roads in Louisiana. Overall, a good agreement was found between the predicted permanent deformations and the field measurements. Finally, the APT test calibrated FE model was used to develop P-D prediction models (transfer function) for pavement base and subbase/subgrade materials. These materials were classified into four categories: stabilized base materials (e.g., stabilized blended calcium sulfate materials); unbound base materials (e.g., crushed limestone); treated subbase/subgrade materials (e.g., lime, lime/fly ash, and cement treated soils); and untreated subgrade soils. The developed P-D transfer functions were verified by predicting the six APT sections and two typical low volume pavement structures. The predicted permanent deformations generally matched well with the field measurements. 17. Key Words Flexible Pavement; Permanent Deformation (Rutting); Stabilized Base; Treated Subbase; Accelerated Pavement Test; Permanent Deformation Test; Finite Element Simulation; Numerical Modeling. 18. Distribution Statement Unrestricted. This document is available through the National Technical Information Service, Springfield, VA 21161. 19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 21. No. of Pages 132 22. Price TECHNICAL REPORT STANDARD PAGE

Finite Element Simulation of Structural Performance on Flexible Pavements with Stabilized Base/Treated Subbase Materials under Accelerated Loading

Documents

flexible pavement

permanent deformation

stabilized base

treated subbase

accelerated pavement

permanent deformation