The influence of the water on the pavement performance were clarified and then the structural design method for airport asphalt pavements were established under the high groundwater level.
　The following conclusions were obtained.
(1)The asphalt concrete surface course deteriorates much severely as the groundwater level increases in the base course. Increase of its thickness improves the durability.
(2)The bearing capacity of both granular base course materials and subgrade material decreases with an increase of the groundwater level. Its stabilization is an effective countermeasure.
(3)The load carrying capacity of the asphalt pavement decreases as the groundwater level increases, especially in case of having granular base course. When the pavement is fully submerged, the elastic modulus of subgrade, base course decreases to 80%, 70% of that under the unsoaked condition, respectively.
(4)In case that the groundwater level rises into the subgrade, the subgrade design CBR must be lowered; 80% of the usual value in thecompletely submerged condition.
(5)When the groundwater level is susceptible to rise into the base course, the asphalt stabilized material must be used as the base course. Furthermore, the subbase material should be partially replaced with the asphalt stabilized material.