The Incheon bridge will be an exemplary example of a cable-stayed offshore bridge located in the Rep. of Korea. It connects the Songdo city to the Incheon International Airport. Pile foundation of Incheon bridge is consisted of large diameter drilled shafts, up to 55m deep and 3.0m in diameter, which were embedded in rock. This paper describes the load distribution and deflection of drilled shafts subjected to lateral loads in marine clay. The emphasis was on quantifying the cyclic lateral soil resistance placed from the piles to surrounding soils based on one-way and two-way cyclic loading tests performed on small and full-scaled drilled shafts. The cyclic loading tests included four test piles founded in weathered and soft rocks through soft clay and silt: three of the test piles (LTP-1, LTP-2, LTP-3) were the small-scale driven piles (diameter=1.016m, length=26m); the other (LTP-4) was the full-scale drilled shaft (diameter=2.4m, length=45m). All test piles were performed by the one-way loading method except for LTP-3 (two-way). Based on the test results, lateral cyclic behaviors of offshore drilled shafts in marine clay are discussed and compared with existing methods.
In South Korea, a number of huge construction projects such as land reclamation projects for an international airports, high-speed railways, and harbors are in progress in urban and coastal areas. Drilled shafts are frequently used in those areas as a viable replacement in driven piles for two applications: Deepwater offshore foundations, and foundations in urban areas. Recently, larger diameter drilled shafts have been widely used as a foundation for bridges to support both large axial and lateral loads and requested for dynamic designs as an important earthquake prevention measure. Although many researches have been carried out on pile under static lateral loading, less is known about cyclic lateral behavior of the drilled shafts.