Assessment and enhancement of asphalt pavement resilience to flooding
Creators: name: Chen, Xiao
Publisher: name: No Publisher Supplied
Year: 2025

description: Global climate change poses significant challenges to the durability and integrity of transportation infrastructure, with flooding being one of the most critical threats. Traditional flexible pavement, one of the most commonly used types worldwide, is particularly vulnerable to flooding. However, current pavement design does not account for the effects of flooding, which often accelerates pavement deterioration and leads to substantial repair and rehabilitation costs. With the increasing intensity and frequency of flooding in recent decades and the budget constraints from transportation agencies, it is crucial to evaluate and mitigate the flooding impact on flexible pavements. Such assessments are vital for incorporating flooding considerations into future pavement design processes, reducing environmental impacts and minimizing associated costs. This research assesses and enhances pavement resilience to flooding by analyzing the multifarious impacts of flooding on roadway pavement performance and proposing the corresponding mitigation strategies. It integrates the development of hydrological, mechanistic, and hydro-mechanical models with comprehensive laboratory experiments to achieve these objectives.The flooding impacts assessed in this research include surface inundation and subsurface saturation. The surface inundation can be divided into surface material degradation and hydraulic scouring. The material degradation caused by prolonged exposure to floodwater was evaluated through laboratory experiments on asphalt mixtures subjected to various inundation periods. Mechanical testing results revealed that the strength of surface material had reduced with the increase in soakage time. The surface hydraulic scouring effect, which occurs in saturated asphalt materials under traffic loading, was characterized by integrating hydro-mechanical model with laboratory testing. It was found that the magnitude of maximum pore water pressure (PWP), whether inside or at the interface of the asphalt materials with relatively high air voids, can range from 100 kPa to 300 kPa under various field conditions. This pressure is sufficient to significantly reduce both the indirect tensile strength and the interface shear strength under repeated loading.Subsurface saturation effects can be categorized into subsurface weakening and subgrade erosion, both of which occur during the recovery period—from the receding of floodwater from the pavement surface to the restoration of subsurface material moisture levels to pre-flooding conditions. Evaluating subsurface saturation requires capturing the variations in subsurface saturation profiles during the inundation and recovery phases. In this research, these profiles were characterized by integrating laboratory experiments with hydrological modeling. Case analyses were performed on flooded pavement in Florida (FL) and North Carolina (NC). With saturation profile variations, a mechanistic model that considers the moisture-stress-suction dependency of unbound material modulus was used to calculate critical pavement responses during recovery. The effectiveness of this modulus model was justified by comparing predicted deflection with field measurements under FWD load. The critical pavement responses from the mechanistic model were further used for quantifying subsurface weakening damage. Analyses found that the asphalt fatigue cracking damage increased by 1.16 times in the FL case and 1.08 times in the NC case, while the subgrade rutting damage rose by 1.38 times in FL case and 1.82 times in NC case. On the other hand, with saturation profile variations, the hydro-mechanical model was adopted again to analyze the PWP at subgrade, which was further correlated with mass migration to indicate the subgrade erosion potential.To mitigate flooding damage, this research proposed an inverted pavement structural design and post-flooding traffic operation strategies. Compared to conventional pavement, the increases in critical pavement responses for inverted pavement were significantly smaller after prolonged flooding, demonstrating its potential to enhance resilience against subsurface weakening. From the traffic operation perspective, falling weight deflectometer (FWD) deflections were correlated with critical pavement responses. By conducting FWD testing on pavement after flooding, damage ratios can be estimated and compared to agency-determined thresholds. Subsequently, measures such as imposing truck weight limits or controlling traffic volume can be implemented to reduce the damage caused by subsurface weakening.