Abstract:
London City Airport’ s sole runway is perched precariously on a narrow finger of land in central London near to the old City on the edge of the River Thames. Formally the central quay of the Royal docks, the runway is surrounded by water and redundant deep cargo berths. The docks were heavily bombed by the Luftwaffe during World War II and later abandoned before conversion to an iconic airport in the late 1980’ s.
The owner’ s need to increase airport capacity drove the addition of a new taxiway parallel to the runway. Lack of available dry land meant it taking the form of a 20-acre reinforced concrete deck over the historic dock supported by piles. The resulting marine site was inaccessible directly from land and operated to keep flights uninterrupted during daytime or nearby London residents undisturbed at night.
This paper will present a recent experience of piling in a marine environment in London, UK, where over 1000 piles were installed into the existing docks using cased rotary bored techniques under polymer support fluid.
Construction of the piles in such proximity to the operational airport required strict and out of hours working be observed and many restrictions imposed on the works.
Due to the complex nature of the geology across a site that extended over 3000 ft in length, piles were either located in the Thanet Sand Formation or in the underlying Chalk. Every pile included a permanent steel casing from the water level down through the dock bed, terminating beneath the 100-year-old dock basin and forming an integral part of the RC deck structure that was designed part submerged thus leading to tricky submarine elements.
A bumpy ride with many challenges, this paper will discuss the extraordinary level of technology deployed to investigate them and how they were successfully overcome.