DESIGN OF ALTERNATIVE DEEP FOUNDATION FOR SRC OFFICE BUILDING, SOUTH JAKARTA

Abstract

The SRC Office Building in South Jakarta was originally designed with 300 × 300
mm square precast piles installed to a depth of 20 m. During construction, however,
the piles reached only 16–18 m, resulting in an inadequate Safety Factor of 1.057,
which is below the minimum requirement of 2.5 specified in SNI 8460:2017.
Therefore, an alternative foundation design was required. This study compares the
performance of spun pile and bored pile foundations in terms of axial bearing
capacity, required number of piles, settlement, safety factor, and construction
method. Axial bearing capacity was evaluated using the Meyerhof and Reese &
Wright methods with pile diameters of 0.4, 0.6, and 0.8 m. Spun piles were analyzed
at depths of 24 m (without a stiff soil lens) and 20 m (with a stiff soil lens), while
bored piles were analyzed at 24 m. Settlement was calculated using the Poulos and
Davis method and verified through PLAXIS 2D. Under the critical loading
condition at Joint 8, the 0.4 m spun pile at 24 m provided an ultimate bearing
capacity of 2,412.272 kN per pile, requiring four piles, with a settlement of 3.864
cm and a Safety Factor of 2.9. At 20 m, the required number of piles increased to
five, with a settlement of 9.724 cm. The 0.6 m bored pile achieved an ultimate
bearing capacity of 3,759.780 kN per pile, requiring two piles, with a settlement of
4.869 cm and a Safety Factor of 2.6. The results show that both foundation types
satisfy the design requirements in the absence of a stiff soil lens. However, when a
stiff soil lens obstructs pile driving, the bored pile foundation is the more suitable
alternative because it can penetrate the layer and reach the design depth.