Sekolah Citra Kasih Manado

Bored pile foundation for the new Citra Kasih School building in Manado: 75 piles of Ø 600 mm with an effective length of 10 metres, carried out in stages that followed the structural works above, from November 2023 to April 2024.

The soil profile shaped every decision on site. Roughly 2.5 metres of loose fill sits at the surface, and below it the ground is mixed with boulders all the way to the base of each hole. The toe of every pile ends in rock and was cut with a core barrel over the last one to two and a half metres. A single pile could take more than sixteen hours of drilling — far longer than in ordinary clay.

Reinforcement went in as two sections: 6D13 + 6D16 with close spiral spacing in the top four metres, then 6D16 below. Concrete was placed through an 8-inch tremie pipe, and the volume of every pile was recorded and compared with the theoretical volume of the hole. In boulder ground the difference is large, because concrete fills the voids between boulders — which is precisely why the figure is logged pile by pile. After casting, the coordinates of each pile were resurveyed as as-built data.