Not all piles can be jacked. GEOSS specifies:
The GEOSS document is organized around six pillars. For jacked piles, these are non-negotiable:
Adhering to GEOSS good practice is not optional in Singapore – it is increasingly referenced by BCA and LTA in project conditions. Not all piles can be jacked
Additionally, all jacked piling works must be supervised by a Geotechnical Engineer (GE) registered under BCA’s IES/ACES scheme, with a copy of the GEOSS checklist submitted to QPS (Qualified Person Supervision) daily.
Jacked piles are displacement piles—they squeeze soil sideways, which can uplift previously installed piles (especially in marine clay). Additionally, all jacked piling works must be supervised
GEOSS-approved sequence good practices:
| Site Condition | Recommended Sequence | |----------------|----------------------| | Single isolated pile | No special sequence. | | Group of piles (≤9) | Center-outwards or spiral. | | Long pile rows (e.g., for retaining walls) | Staggered, with pre-drilled pilot holes (50–70% pile diameter) to reduce displacement. | | Adjacent to MRT / existing building | Install “sacrificial” or “guard” piles first, then inner piles. Use extremely low jacking rates (<5 mm/s). | Jacked piles are displacement piles —they squeeze soil
Critical: Re-jack all piles in a group after 24–48 hours of set-up to confirm no loss of capacity due to heave.
Unlike driven piles, jacked piles require a controlled, steady penetration rate.