5th Runway Embankment Settlement Hartsfield–Jackson Atlanta International Airport

As part of ongoing improvements at Hartsfield-Jackson Atlanta International Airport (HJAIA), a new 2,744m (9,000 feet) long Runway (10–28) and parallel Taxiway (U) are in the process of design and construction. The new runway/taxiway will be located 1,280m (4,200 feet) south of existing runway RW 9R/27L and will be connected to Taxiway R by new parallel Taxiways W and Z aligned in a north-south direction. Post, Buckley, Schuh & Jemigan (PBS&J) is the design engineer for the eastern portion of the runway which is approximately 1,067m (3,500 feet long). Willmer Engineering Inc. (Willmer) performed the geotechnical investigation and analyses for the eastern portion of the new runway/taxiway, two new north-south taxiways, a new non-licensed vehicle road (NLVR) tunnel and Loop Road tunnel to be constructed under the two new taxiways, and a mechanically stabilized earth (MSE) wall to retain a portion of the runway fill to permit a road alignment. For the eastern portion of the new runway/taxiway, as much as 21.3m (70 feet) of new fill will need to be placed over a residual soil profile with up to 15.3m (50 feet) of compressible thickness. The extensive site investigation revealed extremely variable subsurface soil conditions. Rock (auger refusal) was encountered at depths ranging from a few feet to almost 30.5m (100 feet) below existing grades. The combination of thick fills and variable thickness of compressible residual soils resulted in large differences in estimated total settlements and differential settlements along the alignment of the runway and taxiways. Another component of concern was the long-term settlement due to secondary consolidation of the residual soils under constant loading. It has been reported that certain portions of the existing taxiway system had experienced 203mm (8-inches) of settlement over a 20-year period. Long term settlements were a major issue regarding design grades along the runway and taxiways.