Behaviour of airfield pavement subgrades under load test

The US Federal Aviation Administration's National Airport Pavement Test Facility (NAPTF) was constructed to provide full-scale pavement response and performance data under new generation aircraft loading for development and verification of airport pavement design criteria. During the first series of traffic tests, four flexible pavement test sections (two low-strength subgrade and two medium-strength subgrade test sections) were subjected to six-wheel and four-wheel gear loading to assess the relative severity effects. Trench sections were opened at the completion of traffic testing for conducting forensic investigations. In this paper, the effect of full-scale accelerated heavy aircraft gear trafficking on the NAPTF unbound aggregate and fine-grained subgrade layer material properties (referred to as geomaterials) is discussed. The results indicate that the in situ dry densities and moisture contents have decreased in the crushed stone base as a result of trafficking whereas the dry densities of the sub-base (grey quarry blend fines) layer have increased. The low-strength subgrade California Bearing Ratio (CBR) has increased as a result of trafficking, whereas the medium-strength subgrade CBR has decreased. These results can be used to develop input parameters for NAPTF pavement structural modelling and analysis.