Investigation of Environmental and Dynamic Loading Impacts on Flexible Pavement Responses in Cold Climate Conditions

• Author / Creator

  Shafiee, Mohammad H

• Flexible pavement design methods have undergone a paradigm shift with particular attention to mechanistic-based approaches, which are based on the actual pavement’s structural behaviour and reflect the pavement performance. The mechanistic design procedures rely on the pavement’s critical responses for prediction of pavement distresses, making response measurement and prediction significantly important for pavement engineers. While a limited number of facilities around the world are capable of in-situ measurement and evaluation of pavement responses, the lack of comprehensive information on the effect of static and dynamic loads, especially on cold region pavements, concerns pavement engineers and researchers. The current study was conducted in an attempt to address the impact of vehicular and Falling Weight Deflectometer (FWD) loads on pavement responses under different environmental conditions, as well as to investigate the behaviour of pavement responses due to environmental loading. As part of this research, a series of controlled vehicle tests were conducted at the Integrated Road Research Facility (IRRF), a full-scale test road equipped with structural and environmental pavement instruments located in Edmonton, Alberta, Canada. Also, several rounds of FWD tests were implemented at instrumented sections of the IRRF to investigate the seasonal variation of recorded stresses and strains. Promising results were obtained when applying advanced frequency domain and time-frequency domain analysis methods to evaluate the loading frequency of vehicle loads based on the field data. Analyzing the frequency at multiple speeds and at different depths from the surface using Fact Fourier Transform (FFT) led to improved dynamic modulus estimation accuracy. In addition, analyzing the asphalt longitudinal strain frequency using Continuous Wavelet Transform (CWT) and Short-Time Fourier Transform (STFT) showed the advantage of time-frequency domain techniques in comparison to traditional time-to-frequency conversion methods. Reasonable agreement between predicted and measured FWD-induced responses was achieved using the laboratory-determined asphalt master curves and backcalculated moduli of base and subgrade layers for dynamic simulation of pavement structure via 3D-Move software. Also, by incorporating the FWD stress time histories, an axis-symmetric Finite Element Model (FEM) was developed in ABAQUS and the prediction results were compared against the in-situ measured ones. Monitoring the seasonal variation of strains at the bottom of Hot Mix Asphalt (HMA) and stresses within the base and subgrade layers when subjecting the pavement to FWD clearly showed the significant impact freeze/thaw cycles had on the recorded values. It was found that during the thawing period, the horizontal and vertical strains can be almost 17 and 11 times larger than their counterparts in cold months. Results from this study also indicated that the stress on top of the base layer can increase more than two times during the thaw period. In addition, the collected data over the course of sixteen months emphasized the significant effect of temperature fluctuation, in absence of traffic loading, on generating strains in three directions under the HMA layer. This analysis was fruitful and indicative of HMA thermal properties in the field.

• Subjects / Keywords

  • Pavement
  • Asphalt
  • Stress
  • Strains

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3MW28R29

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.