As a consequence of climate change, the frequency and intensity of flooding events across the United States have been increasing over the past decades. Understanding the impact of these flooding events on the performance of flexible pavement networks is crucial for the design and maintenance of these structures. Flooding increases the degree of saturation of pavement layers, which affects the mechanical behavior of the materials and accelerates the deterioration rate. The focus of this dissertation is the impact of flooding events on the performance of flexible pavement structures at both the project and network levels, using a Mechanistic-Empirical (ME) pavement analysis framework.A comprehensive literature review highlighted the limitations in current modeling approaches and underscored the need for an improved analysis system. To address these gaps, a framework was developed to incorporate the effects of flooding events on the performance of flexible pavement structures using the ME analysis procedure. This framework proposed four major modifications to the standard Mechanistic-Empirical Pavement Design Guide (MEPDG) approach, including (i) a hybrid analysis increment scheme to capture short-term flooding effects, (ii) adjustments to the Resilient Modulus (MR) of unbound layers due to increased saturation levels, (iii) modifications to the rutting prediction model for saturated pavement materials, and (iv) accounting for changes in traffic patterns during flooding events. The Unified Pavement Distress Analysis and Prediction System (UPDAPS) program, which is a ME-based pavement analysis tool, was developed as a baseline for the analysis of this research. The proposed framework was implemented into the analysis engine of the UPDAPS program, resulting in a modified version called the UPDAPS-Flood program. The distress prediction results of the UPDAPS-Flood program were validated by simulating several pavement structures from the New Orleans area under the flooding caused by hurricanes Katrina and Rita. At the project level, the UPDAPS-Flood program was used in a case study in Miami-Dade County, Florida, to simulate the effects of nine major flooding events on a newly constructed flexible pavement structure. The findings showed significant increases in rutting, fatigue cracking, and International Roughness Index (IRI) distresses due to these flooding events. The results emphasized the advantages of the UPDAPS-Flood program in analysis and design of the flexible pavement structures in the flood-prone areas. At the network level, UPDAPS-Flood program was employed to evaluate the resiliency of 10,650 flexible pavement structures across the contiguous United States. The simulation results showed a higher loss of service life for pavement networks in the Long-Term Pavement Performance (LTPP) Wet/Freeze region, areas near major U.S. rivers (e.g., the Missouri and Mississippi rivers), and along the eastern coastline. This observation was attributed to the more frequent and severe flooding events recorded in these areas, primarily caused by river flooding, coastal flooding, or high precipitation. The analysis showed an average nationwide loss of service life of nine months for pavement structures due to flooding events. Additionally, the results indicated that highly flooded sections experienced significant performance losses, emphasizing the importance of considering flooding events in pavement design and maintenance frameworks, particularly in flood-prone areas. Moreover, a sensitivity analysis was conducted to evaluate the impact of key input parameters in the UPDAPS-Flood program on the calculated resiliency of the flexible pavement network against flooding events. The results showed a direct correlation between the reduction in MR of saturated unbound layers and the accumulated flooding damage. The results also highlighted the critical role of the effective drainage systems in mitigating the flooding damage to the pavement network. Geosynthetic reinforcement of the unbound base layer was also investigated as a potential strategy to improve pavement resiliency against flooding events. Laboratory test results showed that geosynthetic reinforcement increased the MR of base materials by 47% and reduced plastic strain by 23.4%, offering a promising solution to improve pavement performance under flood conditions. In addition, a geosynthetic reinforcement model was implemented in the UPDAPS-Flood program by integrating a Finite-Element Method (FEM)-based pavement structural response model. The simulation results on two typical pavement structures in Michigan showed that effect of geosynthetic reinforcement on improving the pavement resiliency against flooding events was dependent on the structural capacity of the pavement. In the thinner pavement sections, the geosynthetic reinforcement not only mitigated flooding damages but also improve the overall performance of the pavement, while in the thicker pavement sections, it did not show significant improvement in the predicted distresses under flooding scenario.
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