The alternative pavement design [4] is based on a combination of improving the subsoil
conditions and using a stress distributing bound subbase layer. To reduce possible differential
settlements the subgrade at the location of the 5th runway will be improved by ‘pre-loading’ using
a new technique based on vacuum consolidation. The pre-loading is achieved by sealing off the
soil at the top by a membrane and pumping water out of the soft layers from a depth of about
seven meters using a grid of vertical drainage channels. Further elaboration on this special
technique is outside the scope of this paper.
To avoid reflective cracking a high quality unbound aggregate interlayer is introduced
between the bound subbase, and asphalt concrete base and surface layers. As planned
maintenance is growing in importance for optimal use of all available runways, the likelihood of
unpredicted localized distresses caused through the use of a thick bound base layer will be
minimized using the alternative pavement design.