The Geotechnical Society of Singapore (GeoSS) published a foundational guideline titled " Good Practice for Installation of Jacked Foundation Piles in Singapore " (October 2015) to standardize the use of this eco-friendly piling method . The following technical paper outlines the core principles and "good practice" standards derived from GeoSS recommendations and local industry standards. Technical Paper: Good Practice for Jacked Pile Installation in Singapore 1. Introduction Jacked piling has over 20 years of history in Singapore, evolving from small-scale underpinning to supporting high-rise structures. It is favored for being vibration-free, air pollution-free, and generating low noise levels, making it ideal for urban infill sites. Modern jacking machines in the local market now reach capacities of up to 800 tonnes . 2. Machine Capacity and Operational Limits Safety Margin: GeoSS recommends that jacking machines be operated at approximately 75% of their maximum rated capacity to ensure stability and mechanical longevity. Machine Requirements: Specialist builders must maintain a regular maintenance regime and provide daily, monthly, and yearly checklists to ensure equipment reliability. 3. Installation and Termination Criteria The termination of a jacked pile is not solely based on depth but on a rigorous "set" verification process: Jacking Force ( Pjcap P sub j ): The pile is typically jacked in steps until the force reaches 2.0 to 2.5 times the Working Load (WL) . "Set" Definition: After reaching the target force, the pressure is released and reapplied without pause. Criterion: The downward movement between the initial jack and the re-jack must not exceed 10 mm with a minimum holding time of 30 seconds . Consistency: GeoSS recommends achieving two consistent sets before final termination. 4. Ground Monitoring and Mitigation As jacked piles are displacement piles, they can cause significant lateral soil movement and heaving, especially in soft clay or dense sand. Monitoring: Continuous monitoring of ground movement and adjacent structures is mandatory to prevent damage. Protective Measures: If displacement risks are high, engineers may utilize relief wells or pre-boring to mitigate excessive soil pressure. Heave Control: In formations like Bukit Timah Granite, recorded heaves of 10 mm to 60 mm have occurred, requiring verification through additional working load tests. 5. Design and Compliance Standards: Designs must comply with Eurocode 7 (EC7) and the National Annex, which superseded SS CP4 in April 2015. Settlement Limits: Standard acceptance criteria typically limit pile head settlement to 15 mm at 1.5x WL and 25 mm at 2.0x WL . 6. Conclusion Following GeoSS good practices ensures that jacked piles provide superior verticality and stability while minimizing the environmental impact on Singapore's dense urban landscape. Successful installation relies on matching machine capacity to site conditions and strictly adhering to multi-cycle termination criteria.
Geoss Good Practice for Installation of Jacked Foundation Piles in Singapore Abstract This paper examines best-practice recommendations—hereafter referred to as “GEOSS Good Practice”—for the installation of jacked foundation piles in Singapore. It synthesizes geotechnical, structural, environmental, and construction-management considerations specific to Singapore’s geology, regulatory context, and urban constraints. Recommendations are practical, prescriptive, and intended for design engineers, contractors, site supervisors, and project owners involved in piled foundation works where jacking (hydraulically driven, displacement or pre-bored) methods are employed. Keywords: jacked piles, displacement piles, geotechnical practice, Singapore, pile installation, ground movement, quality assurance.
Introduction Jacked foundation piles (hydraulically driven displacement piles and pre-bored jacked piles) are widely used in Singapore for deep foundations where vibration minimization, tight site access, and load performance are critical. Singapore’s reclaimed land, alluvial deposits, marine clay layers, and dense urban fabric require tailored procedures to mitigate settlement, ground disturbance, and risks to nearby structures and utilities. This paper outlines GEOSS Good Practice covering site investigation, pile selection and design, installation methodology, instrumentation and monitoring, quality control, environmental and safety management, and post-installation validation.
Site Investigation and Ground Characterization 2.1 Objectives The Geotechnical Society of Singapore (GeoSS) published a
Establish stratigraphy, strength and stiffness profiles, groundwater conditions, and variability to depths beyond the targeted pile tip. Identify potential obstructions, fill zones, organic layers, and peat pockets common in reclaimed or former mangrove areas.
2.2 Recommended Investigations
Borehole spacing and depth: For typical urban piled projects, boreholes at 25–50 m spacing extending to at least 3 times expected pile length or to competent bearing strata, whichever is deeper. Increase density near known variability, adjacent structures, or where piled load is high. SPT/CPT: Cone Penetration Testing (CPTu with pore pressure) is preferred for continuous profiling; supplement with SPT in gravelly layers where CPT refusal may occur. Laboratory testing: Consolidation (oedometer), triaxial or UU tests, index tests (grain size, Atterberg limits), and cyclic/undrained strength tests where soft marine clays exist. Groundwater: Measure phreatic level and seasonal variation; pore-pressure dissipation tests where applicable. Geophysical surveys: Where utility mapping or large lateral variability exists, use GPR or resistivity. Obstruction detection: Adjacent to reclaimed areas or old structures, include trial coring or sonic logging. Introduction Jacked piling has over 20 years of
2.3 Interpretation for Jacked Piles
Determine suitable pile type (displacement vs. bored jacked) based on presence of obstructions, stratigraphy, and environmental constraints. Identify likely penetration resistance trends to estimate driving/jacking forces and potential for refusal or buckling.
Pile Type Selection and Design Considerations 3.1 Types and Applicability provide end-bearing and side resistance.
Closed-ended steel tubular displacement piles (driven/jacked) — suitable for urban sites needing low vibration; provide end-bearing and side resistance. Precast concrete piles installed by jacking into pre-bored holes where obstructions or hard strata require pre-boring. Composite piles (steel shell with concrete infill) — useful for marine clay with high corrosion risk mitigated by proper cover and materials.
3.2 Design Parameters