The Expansion of Abu Dhabi International Airport

The piling works for this project is considered one of the largest foundation projects undertaken in the gulf region. The scope of work involved the construction of more than 7,000 piles for the proposed Midfield Terminal Building, car park, gate house structures, access roads and bridges. The upper rock strata at the site contains large amount of cavities that range in depth from surface to deep, and vary in size from small isolated cavities to large interconnected cavities.

One of the greatest challenges in the design was to transfer heavy column loads through the rocks that contain cavities and weak zones into the lower competent bedrock. Installation of large diameter concrete bored piles through the cavernous rock media was also a great operational challenge.

A comprehensive investigation program involving probing for cavities had been carried out prior to construction. The findings of the probing investigation were analyzed using sophisticated spreadsheets as well as a specialized geographical information system program, ArcGIS. Based on the findings, solutions for cavity treatment and pile installation were adopted.

The scope of work involved the construction of more than 7,000 piles for the proposed Midfield Terminal Building, car park, gate house structures, access roads and bridges. The piles ranged in diameter from 1.0 m to 1.5 meters and in length from 15.0 m to over 30.0 m. Extensive working and instrumented non working pile load tests, as well as integrity caliper logging and sonic tests were carried out.

The unconfined compressive strength for rock samples extracted from the site varied significantly from less than 0.5 MPa to over 15 MPa. The rock quality designation (RQD) values also varied significantly from 0% to 100% with the majority of zero RQD values recorded above the 10.0 m NADD elevation. The measured ground water level varies across the site generally from +2.0 to +5.5 m NADD.

The final design of the piles was carried out taking into account all structural and geotechnical aspects. Moreover, the design and performance were verified based on pile load testing on preliminary and working piles.