The Geotechnical Society of Singapore (GeoSS) has established specific guidelines for the installation of jacked foundation piles to ensure structural safety and serviceability within Singapore’s unique geological landscape. Jacked piles are favored in urban areas due to their low noise, negligible vibration, and minimal soil disposal. 1. Pre-Installation and Ground Considerations
Successful installation begins with a thorough understanding of the site’s soil profile to prevent damage to adjacent structures.
Site Investigation: Designers are encouraged to conduct adequate site investigations, including probe holes at every pile group location to detect potential voids or cavities.
Machine Stability: The stability of the jacking machine must be verified, especially on soft ground. Specialist builders must maintain high-capacity rigs; for example, G3 category specialists require rigs with a minimum 400-ton counterweight.
Maintenance: Rigs must undergo a regular maintenance regime with daily, monthly, and yearly checklists to ensure they remain in peak condition. 2. Installation Procedures and Sequence
The installation process must comply with Eurocode 7 and specific local good practices.
Alignment: Piles must never have their alignment adjusted by force during the jacking process.
Verticality: Continuous checks on pile verticality are essential throughout the installation.
Jacking Sequence: For large pile groups, jacking should proceed from the inside out or in a consistent direction (e.g., left to right) to manage ground displacement.
Negative Skin Friction: If penetrating consolidating soft soil, designers must account for potential downdrag forces (negative skin friction) that may reverse the direction of force in the long term. 3. Termination and "Set" Criteria In Singapore, piles are typically jacked with a force ( Pjcap P sub j
) adjusted in steps up to 2.0 to 2.5 times the working load (WL).
Practical Refusal: Jacking continues until practical refusal is reached. The load is then released and reapplied to measure the "set".
Set Criteria: A pile is generally considered "set" if the downward movement does not exceed 10 mm (some guidelines specify 5 mm) during a holding time of at least 30 seconds.
Consistency: GeoSS recommends achieving two consistent sets before termination.
Short Piles: If termination criteria are met but the pile is significantly shorter than the design depth, the designer must assess if the shallower depth is acceptable. 4. Quality Control and Safety
Stringent safety and quality measures are required by the Ministry of Manpower (MOM) and Building and Construction Authority (BCA).
Monitoring Pile Heave: Adjacent jacking actions can cause previously installed piles to heave, potentially separating the pile base and losing end bearing. Monitoring for heave is critical, and measures like pre-boring or relief wells should be used if necessary.
Supervision: Pile testing must be conducted under the direct supervision of a designated person.
Safety Barriers: Effective measures, such as warning signs and restricted access, must be implemented to keep personnel away from the test area while loading is in progress.
Integrity Testing: After installation, tests like Sonic Logging, PDA/PIT, or Full Coring are used to assess the structural integrity of the piles. 5. Performance-Based Design
Current standards emphasize performance-based design where designers review instrumented Ultimate Load Test (ULT) results to verify design parameters.
Settlement Limits: Typical allowable pile head settlements are 15 mm at 1.5 times the working load and 25 mm at 2.0 times the working load.
Verification: Once design parameters are verified via ULT, the Qualified Person (QP) must obtain written concurrence and submit interpretation reports to the BCA before commencing working pile installation. The Geotechnical Society of Singapore ( GeoSS )
The Geotechnical Society of Singapore (GeoSS) provides guidelines for the installation of jacked piles, emphasizing that it is a "friendly method" due to being vibration-free, air pollution-free, and low-noise. This method is particularly suitable for congested urban environments in Singapore, like high-density condominium developments. Core Installation Guidelines
Machine Capacity: It is recommended that the jacking machine be used at approximately 75% of its maximum capacity. In Singapore, machines with capacities up to 800 tonnes are available.
Platform Preparation: Because jacking machines are heavy, the working platform must be of high quality, with rigorous compaction and proper site drainage to ensure stability.
Ground Movement Control: To protect sensitive adjacent structures, GeoSS recommends:
Installing relief wells at strategic locations (e.g., at boundaries near neighboring structures). Pre-boring at the pile point.
Constructing an opened trench or temporary earth retaining walls if necessary.
Continuous Monitoring: During the first pile installation, a trial should be conducted to observe performance. Ongoing monitoring of both ground and building movement is required throughout the piling works. Termination and Technical Standards
Termination Criteria: Designers typically specify required pile penetration depth based on site investigation (SI) boreholes. The method allows for a form of load testing on every pile by recording the jacked force at every 0.5m to 1.0m of penetration.
Verticality and Precision: Jacked piling is noted for its superior verticality compared to other driven methods.
Maintenance: Piling machines must undergo a regular maintenance regime by a dedicated team, with daily, monthly, and yearly checklists to ensure equipment is always in good condition. Compliance and Regulatory Framework
Codes of Practice: The design and installation of piles in Singapore are governed by the Singapore Standard Code of Practice for Foundations (SS CP 4) and Eurocode 7 (EC7).
Qualified Person (QP) Submission: Upon completion of piling works, the QP must submit as-built piling plans and certificates of supervision within 28 days to regulatory bodies.
Specialist Builder Requirements: For high-capacity projects, Specialist Builders (categories G2 and G3) must maintain a minimum number of jacked rigs with specific counterweight requirements (e.g., 200-ton and 400-ton minimums). AI responses may include mistakes. Learn more
The Geotechnical Society of Singapore (GeoSS) has established comprehensive good practices for the installation of jacked foundation piles, a method favored in Singapore’s urban environment for being vibration-free and low-noise Course Hero Overview of Jacked Piling in Singapore
Jacked piling utilizes a hydraulic jacking system to press pre-formed piles (such as prestressed concrete spun piles or RC piles) into the ground using a dead weight (kentledge) for reaction. While the market now supports machines with capacities up to 800 tonnes, GeoSS recommends operating these machines at no more than 75% of their maximum capacity to maintain safety and efficiency. Course Hero Installation and Termination Criteria
A critical aspect of GeoSS practice is the standardisation of pile termination to ensure geotechnical capacity: Jacking Force: The required jacking force ( cap P sub j
) is typically related to the ultimate geotechnical capacity ( cap P sub u ), often set at 2.0 to 2.5 times the working load (WL) Set Criterion:
A pile is generally considered "set" if the downward movement does not exceed over a holding time of at least 30 seconds Re-jacking Procedure:
The jacking force should be released to zero and re-applied without pause. GeoSS recommends obtaining two consistent "sets" to verify stability. Slenderness Ratio:
Research suggests that for piles where the depth is less than 37 times the diameter, the ultimate capacity ( cap P sub u ) may be less than the jacking force ( cap P sub j isomer-user-content.by.gov.sg Protective Measures for Adjacent Structures
Because jacked piling involves significant soil displacement, GeoSS emphasizes measures to protect nearby buildings, especially in dense residential areas: Relief Wells:
Installing 400 mm to 600 mm diameter bored holes (often using perforated steel pipes) at strategic boundaries to reduce ground movement. Pre-boring: and Old Alluvium.
Pre-drilling at the pile point to a specified depth (e.g., above sensitive utility lines) to minimize displacement. The hole diameter should be slightly smaller than the pile to maintain shaft resistance. Machine Management:
When multiple machines are on-site, they should not be clustered closely together, as this aggregates ground movement risks. Open Trenches:
Using temporary open trenches or earth-retaining walls to contain ground movement within the project boundary. isomer-user-content.by.gov.sg Operational Good Practices Platform Preparation:
Given the massive weight of jacking machines, the working platform must be high-quality, with strict requirements for compaction and site drainage. Verticality:
Continuous checks on pile verticality are essential during the initial jacking stages. Record Keeping:
High-frequency recording of jacking force—typically at every 0.5 m to 1.0 m of penetration—is recommended for quality assurance. isomer-user-content.by.gov.sg Load Testing Standards
GeoSS provides specific guidelines for safe pile load testing, particularly the Kentledge Method
. This includes verifying the geotechnical bearing capacity of the kentledge base itself to prevent sudden settlement or instability during testing. Course Hero used for spun piles in Singapore?
GEOSS Good Practice: Installing Jacked Foundation Piles in Singapore
Jacked piling has become a staple of Singapore’s urban construction landscape. Favoured for being vibration-free
, it is the go-to method for projects near sensitive structures like landed properties or MRT lines. However, its success depends on strict adherence to the Geotechnical Society of Singapore (GeoSS)
guidelines to manage ground movement and ensure pile integrity. Key Installation and Termination Criteria
Proper pile termination is critical to ensure the foundation meets its design load without excessive settlement. Termination Force ( cap P sub j Piles are typically jacked with a force ( cap P sub j ) adjusted in steps to 2.0 to 2.5 times the working load (WL) The 'Set' Criterion:
A pile is considered "set" if its downward movement does not exceed over a minimum holding time of 30 seconds Double Verification: GeoSS recommends obtaining two consistent sets
by releasing the pressure to zero and re-jacking before final termination. Equipment Limits: Jacking machines should ideally be used up to only 75% of their maximum capacity to maintain stability and safety. Essential "Good Practices" for Site Success
Beyond basic installation, several operational practices are vital for high-quality outcomes: No Forced Alignment:
Never adjust a pile’s alignment by force during the jacking process; this can compromise the structural integrity of the pile. Strategic Jacking Sequence: For large pile groups, always work from inside out
or in a consistent direction (e.g., left to right) to prevent trapping soil and increasing ground displacement. Calibration Standards:
Load cells must be calibrated by an accredited laboratory before starting a new project, or every , whichever comes first. Addressing Depth Deviations: If a pile terminates more than 20% shallower
than the approved plan, the designer must submit an amendment plan and may require additional load tests to verify capacity. Protective Measures for Adjacent Structures
Because jacked piles are displacement piles, they can cause significant ground heave. Protecting nearby buildings is a requirement: Relief Wells:
Install bored holes (400–600 mm diameter) at strategic boundaries to allow displaced soil to enter, reducing lateral pressure on neighbouring structures. Pre-boring: Unlike impact hammers
Use pre-boring at the pile point to ease penetration and limit ground movement in dense soil. Active Monitoring:
Continuous tracking of building and ground movement is essential. If unexpected movement occurs, work must stop for engineering rectification.
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.
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
6.1 Adjacent to MRT (LTA Requirement)
6.2 Near Buried Utilities (PUB, SP Group)
6.3 Noise & Vibration (NEA)
Even with perfect jacking, verification is mandatory:
GEOSS requirement: Any pile failing PIT or SLT must be investigated by the QP, and a remedial plan (e.g., additional piles, under-reaming) approved before proceeding.
Unlike impact hammers, jacking uses static hydraulic force. Good practice under GEOSS focuses on three real-time metrics:
Jacked piling (also known as displacement piling) involves installing pre-cast concrete or steel piles into the ground using hydraulic jacks reacting against the weight of the rig or previously installed piles. In Singapore, jacked piles are widely used for:
The method offers advantages over driven or bored piles in Singapore’s soft to medium-dense marine clay, Kallang Formation, and Old Alluvium.