Automated Design-Based Compaction Criteria for Airport Pavements Using FAARFIELD

Abstract

A new computational procedure developed for the Federal Aviation
Administration’s (FAA) FAARFIELD program determines the degree of compaction required
at various depths, based on the specific pavement thickness design and aircraft traffic mix.
This procedure is run at design time and automatically generates a unique schedule of
minimum required densities as part of the design report. The basis for computed compaction
requirements is the compaction index (CI), which is defined as the CBR required at a given
depth for a particular gear load. The procedure implements accepted empirical relationships
between CI and degree of compaction that were developed for cohesive and non-cohesive
soils from historical full-scale compaction data. Within FAARFIELD, the CI is determined as
a function of the layered elastic vertical stress response, making use of the Frohlich’s stress
concentration factor (to correct for different stress distributions) and the beta factor to relate
the computed stress to CBR. The approximate correlation obtained between layered elastic
stresses and CI using this methodology is valid throughout the typical design CBR range and
can be extended to any complex gear type. The method yields compaction criteria that are
reasonable, integrated with the design, and consistent with observed field data.