Non-destructive testing methods and numerical development for enhancing airfield pavement management

Pavements are an essential component of airport facilities. Airport infrastructures serve to safely transport people and goods on a day-to-day basis. They promote economic development, both regionally and internationally, by also boosting tourist flows. In times of crisis, they can be used for societal emergencies, such as managing migration flows. Therefore, airports need pavements in good physical condition to ensure uninterrupted operations. However, interventions on airfield pavements are costly and labor intensive. Aspects of pavement structural performance related to bearing capacity and damage potential remain of paramount importance as the service life of a pavement extends beyond its design life. Therefore, structural condition evaluation is required to ensure the long-term bearing capacity of the pavement. 

The design and evaluation of flexible airfield pavements are generally based on the Multi-Layered Elastic Theory (MLET) in accordance with Federal Aviation Administration (FAA) principles. The most informative tool for structural evaluation is the Falling Weight Deflectometer (FWD), which senses pavement surfaces using geophones that record load-induced deflections at various locations. Additional geophysical inspection data using Ground Penetrating Radar (GRP) is processed to estimate the stratigraphy of the pavement. The integration of the above data provides an estimate of the pavement's performance and potential for damage. However, GRP is not always readily applicable.

In addition, the most important concern in pavement evaluation is the mechanical characterization of pavement materials. At the top of pavement structures, asphalt mixtures behave as a function of temperature and loading frequency. This viscoelastic behavior deviates from MLET and this issue needs further investigation. Therefore, this study integrates measured NDT data and sample data from cores taken in-situ. The pavement under study is an existing asphalt pavement of a runway at a regional airport in Southern Europe. A comparative evaluation of the strain state within the pavement body is performed both at critical locations and at the pavement surface, taking into account elastic and viscoelastic behaviors. Strains are an important input to models of long-term pavement performance, which has a critical influence on aircraft maneuverability. In turn, the significant discrepancies found highlight the need for more mechanistic considerations in predicting the damage and stress potential of airfield pavements so that maintenance and/or rehabilitation needs can be better managed and planned.

Overall, this study highlights the sensing capabilities of NDT data towards a structural health monitoring of airfield pavements. Ground-truth data from limited destructive testing enrich pavement evaluation processes and enhance conventional FAA evaluation procedures. The study proposes a numerical development for accurate field inspections and improved monitoring protocols for the benefit of airfield pavement management and rehabilitation planning.