COMPARATIVE STUDY OF LARGE DIAMETER BORED PILE UNDER CONVENTIONAL STATIC LOAD TEST AND BI-DIRECTIONAL LOAD TEST

Abstract

Bored pile with 1,500 mm diameter were used to support design load of 1000 tons for Tulur Aji Jangkat Bridge, Melak, East Kalimantan and tested using a single level of O-Cell near pile toe. The pile is 53.4 m long and installed through dominantly alluvial sand. The test was performed in two load cycles. The pile was reported failed at 1654 tons (±165% working load) with displacement of upper segment 41.8 mm and bottom segment 46.8 mm. The case was analyzed numerically in 2D using finite element program PLAXIS 8. The FEM model has been calibrated on the basis of the field O-Cell result. Similar material properties were also used to simulate the conventional head-down test (Kenledge) to compare the difference of soil behaviour which is under tension and under compression. There are two curves obtained from O-Cell test result, the base resistance and shaft resistance which must be converted to equivalent top-load curve. The equivalent top-load curve is used to illustrate as if the pile loaded from the pile head such as conventional head-down test. Comparison are presented between the bearing capacity of those two different pile load testing procedures using finite element method. The result shows that the bearing capacity of O-Cell test slightly lower than Kentledge test by about 11%. The differences was due to the fact that the O-Cell test has caused ground tension in upper segment.