Foundation Design of the 151 Story Incheon Tower in a Reclamation Area

Abstract

A 151 storey super high-rise building located in an area of reclaimed land constructed over soft marine clay in Songdo, Korea is currently under design. This paper describes the design process in developing the foundation system of the super-tall tower, which is required to support the large building vertical and lateral loads and to restrain the horizontal displacement due to wind and seismic forces. The behaviour of the foundation system due to these loads and foundation stiffness influence the design of the building super structure, displacement of the tower, as well as the raft foundation design. Therefore, the design takes into account the interactions between soil, foundation and super structure, so as to achieve a safe and efficient building performance.

The site lies entirely within an area of reclamation underlain by up to 20m of soft to firm marine silty clay, which overlies residual soil and a profile of weathered rock. The nature of the foundation rock materials are highly complex and are interpreted as possible roof pendant metamorphic rocks, which within about 50m from the surface have been affected by weathering which has reduced their strength. The presence of closely spaced joints, sheared and crushed zones within the rock has resulted in deeper areas of weathering of over 80m present within the building footprint.

The foundation design process described includes the initial stages of geotechnical site characterization using the results of investigation boreholes and geotechnical parameter selection, and a series of detailed two- and three-dimensional numerical analysis for the Tower foundation comprising over 172 bored piles of varying length using finite element and boundary element methods. The effect of the overall foundation stiffness and rotation under wind and seismic load is also discussed since the foundation rotation has a direct impact on the overall displacement of the tower.