New Songdo city is a master-planned international business center to be developed on 1,500 acres of reclaimed land along Incheon's waterfront, 40 miles south of Seoul, Korea and connected to the new Incheon international airport by an 11.7km highway Incheon 2nd bridge. Pile foundations of high-rise buildings and the Incheon 2nd bridge in new Songdo city consist of large diameter drilled shafts, up to 55m long, which were socketed to rocks. Drilled shafts constructed for high-rise buildings on the reclaimed land were designed by considering only shaft resistance, while those of Incheon 2nd bridge were done by consider end-bearing as well as shaft resistance.

This paper describes the load distribution and settlement of rock socketed drilled shafts subjected to axial loads. The emphasis was on quantifying the bearing capacity placed from the shafts to surrounding rock based on the static bi-directional loading test (osterberg cell test) performed on full scaled drilled shafts. The load tests consisted seven drilled shafts bearing on the weathered rock, soft rock and hard rock; three shafts were installed in the land area and four shafts were done in the offshore area. The results of the seven load tests are presented in terms of load-deformation curves and load transfer curves. Based on such results, the design loads of each site are determined and discussed.


In South Korea, a number of huge construction projects such as land reclamation projects for an international airport, high-speed railways and many harbor constructions are in progress in urban and coastal areas. Drilled shafts are frequently used in those areas as a viable replacement for driven piles for two applications: Deepwater offshore foundations, and foundations in urban areas where the noise and vibration are associated with pile driving.

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