Geoss Good Practice For Installation Of Jacked Foundation Piles In Singapore May 2026

| Standard | Title | |----------|-------| | SS EN 1997-1 | Geotechnical design – General rules | | BCA “Piling” CP 4 (historical reference) | Still referenced for workmanship | | SS EN 12699 | Execution of special geotechnical works – Displacement piles | | LTA Civil Design Criteria | For transport infrastructure projects |

Singapore is not Hong Kong, and it is certainly not London. The GEOSS guidelines acknowledge five unique local challenges:

The GEOSS good practice bridges the gap between international standards (BS EN 14199, Eurocode 7) and Singapore’s legislative reality (Building Control Act, LTA’s Civil Design Criteria). | Standard | Title | |----------|-------| | SS

The GEOSS Good Practice Guide for Pile Foundation (revised 2021) outlines five pillars specifically for jacking:

GEOSS defines termination not by a single number but by a three-part rule: The GEOSS good practice bridges the gap between

Prohibited action: Do not attempt to achieve refusal by suddenly increasing hydraulic pressure. That cracks piles.

| Formation | Characteristic | Jacking Suitability | Good Practice Focus | | :--- | :--- | :--- | :--- | | Marine Clay (Kallang) | Soft, high compressibility | Good (smooth penetration) | Avoid soil heave; control rate. | | Old Alluvium | Dense silty sand/gravel | Fair to Difficult | Pre-boring / jetting assistance allowed. | | Residual Soil / Weathered Granite | Stiff to hard, sandy silt | Good | Monitor set-up (thixotropic strength gain). | The GEOSS Good Practice Guide for Pile Foundation

Good Practice 2.1: Conduct a Jackability Assessment using CPT data. Reject jacking if required force > 1.5 × static pile capacity (to avoid pile head damage).

Unlike impact hammers, jacked piles allow force-guided installation. GEOSS defines three control modes:

| Mode | Condition | Objective | |------|-----------|------------| | Force control | Soft to medium stiff clay (N < 15) | Maintain constant jacking force, record penetration rate (mm/min). | | Rate control | Dense sand / Old Alluvium (N > 30) | Limit penetration rate to < 5 mm/sec to avoid excessive load spikes. | | Stroke control | Final set-up (refusal) | Advance in 50 mm strokes; record final jacking pressure at each stroke. |