ABSTRACT
Precast piles are driven to 23 m depth to improve the capacity of foundations located on saturated liquefiable sands on top underlain by a thick soft to medium stiff clay. Analyses show excessive kinematic moment at borderline of the two layers during liquefaction. It was decided to drive additional shorter piles (12 m) to mitigate liquefaction hoping that kinematic moments shall be reduced within allowable limits. CPTu tests were carried out before and after pile driving. The results show that qc did not change considerably in the top saturated silty sand layer as well as the clayey soil underneath. The friction sleeve, however, increased more significantly due to radial displacement and compaction/consolidation attributed to cavity expansion during pile driving. Analyses showed that pile arrangement was not sufficient to overcome liquefaction during earthquake. However, safety factor increased sufficiently to reduce kinematic moment within the allowable limits. The details of the site operations, CPTu data before and after pile driving, analyses and interpretations are presented and discussed.
