A foundation system for the new terminal 4 building at sky harbor international airport in phoenix, arizona, incorporated subsurfacesupport and space for a proposed rapid transit tunnel, which may beconstructed beneath the groundwater table in a sand-gravel-cobble horizon after the building is finished and in use. Two walls consisting of slurry-assisted drilled shaft caissons were constructed along the sides of the proposed tunnel to provide foundation support for the terminal and to provide stability for possible future tunnel excavation. An inclinometer verified clearance tolerances for the proposed tunnel space that necessitated tight vertical plumbness specifications for the drilled shaft caissons. Placement of concrete in the slurry assisted caissons was verified using nuclear density probes. The presence of rebar splices and varying access tube positions relative to rebar steel required detailed analysis of nuclear density probe response characteristics, special calibration blocks and procedures, and interpretation of density data based on knowledge of the rebar and access tube geometries. This paper appears in transportation research record no. 1277, Modern geotechnical methods: instrumentation and vibratory hammers 1990.
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