Geoss Good Practice For Installation Of Jacked Foundation Piles In Singapore

The Geotechnical Society of Singapore (GeoSS) provides specific guidelines for the installation of jacked foundation piles to manage ground displacement and protect adjacent structures, which is critical in Singapore's dense urban environment.  Key Good Practice Guidelines (GeoSS) 

According to the GeoSS draft guidelines, several proactive measures should be implemented to mitigate the adverse impacts of ground movement: 

Relief Wells: Install bored holes (typically 400mm to 600mm in diameter) at strategic locations, such as boundaries near neighboring services or structures, to provide a path for displaced soil.

Pre-boring: Use pre-boring at the pile point to reduce the force required for installation and minimize soil displacement.

Machine Management: When using multiple jacking machines, avoid clustering them close together to prevent cumulative ground movements.

Platform Quality: Ensure the working platform is of high quality, specifically regarding compaction and site drainage, as jacked machines can be extremely heavy.

Monitoring Programs: Implement rigorous monitoring of ground and building movement throughout the piling process.

Trial Installations: Conduct a trial on the first pile installation to observe ground performance before proceeding with full-scale work.

Recording Data: Maintain records of the jacking force at every 0.5m to 1.0m of penetration to verify performance against design assumptions.  Relevant Reports and Regulatory Documents 

For more detailed technical requirements, you can refer to these official resources: 

Good Practice for Installation of Jacked Foundation Piles (BCA): A key guideline published on October 8, 2015, which aligns with industry best practices. The jacking frame must be plumb within 1:400

GeoSS Guideline on Jacked Piles (Draft): A comprehensive technical draft covering ground movement control and protective measures.

Performance-Based Pile Design Guidelines: A joint circular from BCA, IES, ACES, and GeoSS (2022) regarding ultimate load testing and design verification.

Requirements and Guidelines on Driven or Jacked Piles: The Building and Construction Authority (BCA) updated these requirements as of September 1, 2022.  Guidelines for ST Plan Applications

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 S. L. & Lee

): 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 Geotechnical Engineering Journal

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.

Headline: Setting the Standard: Navigating GEOSS Good Practice for Jacked Foundation Piles in Singapore

In the dense urban landscape of Singapore, where noise sensitivity and strict vibration limits are paramount, jacked foundation piles (also known as jacked-in piles or static pile jacking) have become the preferred solution for many infrastructure and building projects.

However, successful implementation requires rigorous adherence to quality standards. This is where the Geotechnical Engineering Office (GEO) of Singapore provides essential direction through its Good Practice Guide.

Whether you are a geotechnical engineer, a resident engineer, or a contractor, understanding these guidelines is critical for ensuring structural integrity and site safety.

Here is a breakdown of the key "Good Practice" requirements for the installation of jacked piles in Singapore:

GEOSS Good Practice for Installation of Jacked Foundation Piles in Singapore

2. Jacking Rig Setup & Reaction System

• The jacking frame must be plumb within 1:400 – verified by digital inclinometer before each shift.
• Reaction mass: Minimum 120% of rated maximum jacking force. In soft ground (N < 10), GEOSS recommends preloaded counterweight or tie-down anchors to prevent rig uplift.
• Hydraulic oil temperature: Monitored continuously; if > 60°C, pause operations (risk of inconsistent force transfer).

Section 7: Environmental & Neighbourhood Considerations (GEOSS Extended)

Because jacking is silent, complacency is the risk. GEOSS adds a chapter on vibration monitoring – even jacked piles can produce ground-borne vibrations if stones are crushed at the toe. Limits:

• Peak Particle Velocity (PPV) at MRT tunnel invert: <5 mm/s.
• PPV at adjacent buildings (pre-1970 shophouses): <10 mm/s.

If vibrations exceed these, GEOSS requires switching to a slurry wall or pre-drilled pilot hole method before jacking.

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:

1. The Kallang Formation: A thick layer of soft to firm marine clay with high compressibility. Jacking piles here generate positive skin friction and pore water pressure spikes.
2. Boulder Clay (Old Alluvium & Bukit Timah Granite): Hard, heterogeneous layers that can cause eccentric jacking forces.
3. Sensitive Infrastructure: Operating within 10-15 meters of live MRT tunnels requires settlement and vibration limits measured in millimeters (typically <15mm).
4. Noise Regulations: The National Environment Agency (NEA) restricts percussive piling near residential zones, making hydraulic jacking the preferred method.
5. High Load Demand: With super-tall buildings and heavy viaducts, jacked piles (typically spun micro piles, steel H-piles, or precast concrete segments) must achieve ultimate capacities exceeding 10,000 kN.

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).

4.5 Mitigating Ground Heave & Lateral Movement

• Heave control:
  • Re-jack adjacent piles after 24 hours if heave > 20 mm.
  • Sequence: Install interior piles first, then perimeter.
• Lateral displacement:
  • For piles < 3D spacing, install in two stages (wait 1 day between stages).

Part 3: GEOSS-Certified Installation Sequence – Step by Step

Below is the recommended step-by-step procedure for installing a jacked precast concrete spun pile (typical 350 mm dia, 15 m length) in Singapore’s east coast marine clay over Old Alluvium.

3. Key Technical Requirements

10. References

• BCA (2021) – Guidelines on Piling Works (Singapore)
• LTA (2018) – Civil Design Criteria for Railway & Road Structures
• SS EN 12699:2015 – Execution of displacement piles
• Tan, S. L. & Lee, K. W. (2020) – Jacked piling in Kallang Formation, Geotechnical Engineering Journal, Singapore

Prepared by: [Your Name / Company]
Date: [Current Date]
Status: Good Practice Guidance – to be adapted per project-specific geotechnical report.