Geoss Good Practice For Installation Of Jacked Foundation Piles In Singapore ★

Geotechnical Society of Singapore (GeoSS) and regulatory bodies like the Building and Construction Authority (BCA)

Section 1: Why George? The Need for a Singapore-Specific Standard

Singapore is not Hong Kong, and it is certainly not London. The GEOSS guidelines acknowledge five unique local challenges: Settlement benchmarks: daily during works, weekly for 1

| 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. | Good Practice 3

• Settlement benchmarks: daily during works, weekly for 1 month, monthly for 6 months, then quarterly to 1 year.
• Piezometers: continuous logging where consolidation or pore-pressure change risk exists.
• Jacking force and stroke: continuous logging with alarm levels.
• Vibration: continuous logging near sensitive receptors during works.

Good Practice 3.1: Calibrate jack gauges every 3 months or before each major project. Conduct a comprehensive ground investigation: boreholes

Continuous checks on pile verticality are essential during the initial jacking stages. Record Keeping:

• Conduct a comprehensive ground investigation: boreholes, standard penetration tests (SPT), cone penetration tests (CPTu), laboratory testing (grain size, Atterberg limits, consolidation, shear strength) and groundwater monitoring. Singapore’s coastal alluvium, marine clay layers, reclaimed soils and variable sand lenses require thorough characterization.
• Interpret stratigraphy and long-term settlement behavior: identify compressible clay layers (e.g., marine clay), soft peat or organic horizons, and deep sand or rock layers for end-bearing. Quantify expected immediate and consolidation settlements for the structure and adjacent assets.
• Determine pile type and design capacity: select jacked pile diameter, wall thickness, material (steel, concrete, or precast segments), and required toe resistance and shaft friction factoring safety and serviceability. Use limit state design per Eurocode/BS or SS EN adapted to Singapore practice.
• Assess load transfer method: evaluate whether piles will be socketed into dense layers or rely on skin friction, and design for negative skin friction if soft compressible layers are present.
• Utility and subsurface constraints mapping: locate existing utilities, tunnels, and adjacent foundations (records and non-invasive surveys) to avoid clashes and risk to nearby structures.