Geoss Good Practice For Installation Of Jacked Foundation Piles In Singapore

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:

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?

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 Title: GEOSS Good Practice for Installation of Jacked

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) draft guidelines for jacked foundation piles emphasize that their popularity in

stems from minimal environmental impact (low noise and vibration) and cost-effectiveness. Installation must strictly adhere to Eurocode 7 and specific local practices to ensure safety and structural integrity. Key Installation Practices & Termination Criteria

The following good practices are recommended by GeoSS for the installation of jacked piles in Singapore: Jacking Force ( Pjcap P sub j

): Piles are typically jacked in steps to a force of 2.0 to 2.5 times the working load (WL) until practical refusal is reached. Settlement Verification ("Sets"):

The pile is considered "set" if the downward movement does not exceed 10 mm with a minimum holding time of 30 seconds. Apply final 10 mm stroke; record peak jacking pressure

It is recommended to obtain two consistent sets by releasing and reapplying the load without pause.

Installation Sequence: For larger pile groups, it is recommended to jack from the inside out or in a consistent direction (e.g., left to right) to manage ground displacement and potential heave. Alignment & Verticality:

The pile alignment should not be adjusted by force during installation.

Verticality must be monitored, typically requiring a deviation of no more than 1 in 75. Ground Considerations & Risk Management

Ground conditions in Singapore, such as the thick soft soil layers or the stiff Old Alluvium Formation, significantly impact installation.

Negative Skin Friction: If a pile penetrates a consolidating soft soil layer, designers must account for a reversal of force (downdrag) when calculating the required jacked load ( Pjcap P sub j

Adjacent Structures: To protect sensitive nearby buildings from ground movement caused by displacement piles, practitioners may use: Relief wells or pre-boring at the pile point. Open trenches or temporary earth-retaining walls.

Limestone & Voids: In areas with steeply inclined bedrock or potential voids, extra caution and probe holes at every pile group location are advised to establish proper acceptance. Machinery & Quality Control

The Singapore Accreditation Council (SAC) and Building and Construction Authority (BCA) set standards for the equipment used by specialist builders:

Equipment Requirements: Piling specialists (categories G2 and G3) must have jacked rigs with a minimum counterweight of 200-ton and 400-ton respectively.

Maintenance: Rigorous maintenance regimes, including daily, monthly, and yearly checklists, are mandatory to ensure machines are in good condition.

Ultimate Load Tests (ULT): These are essential to verify design parameters. If actual verified parameters are better than the optimistic design set, an amendment submission may be required.

Geotechnical Society of Singapore (GeoSS) Building and Construction Authority (BCA)

provide guidelines for the installation of jacked foundation piles to ensure structural safety and minimize environmental impact Course Hero

. Jacked piling is preferred in urban areas due to its vibration-free, low-noise, and air-pollution-free nature Course Hero Core Installation Requirements According to the GeoSS Guideline on Jacked Piles , installation must adhere to these key practices: Jacking Capacity

: It is recommended that jacking machines operate at approximately 75% of their maximum capacity

to maintain machine health and ensure successful installation Course Hero Installation Sequence ( c_u )

: For large pile groups, the recommended sequence is from the inside out

or in a specific direction (e.g., left to right) to manage soil displacement and prevent heave Course Hero Alignment and Verticality

: Piles must be checked for verticality throughout the process. Crucially, their alignment should never be adjusted by force during installation Course Hero : Piles are typically joined by several sections together as penetration progresses Final Settlement and "Set" Criteria

The "set" of a jacked pile is verified through a rigorous re-jacking process to confirm stability Course Hero The pile is jacked to a force ( cap P sub j ) usually between 2.0 to 2.5 times the Working Load (WL) until practical refusal Course Hero

The pressure is released to zero and immediately re-applied.

The pile is considered "set" if the downward movement during re-jacking does not exceed with a minimum holding time of 30 seconds Course Hero Engineers typically recommend achieving two consistent sets for final acceptance Course Hero Risk Mitigation and Monitoring

To manage challenges unique to displacement piles in Singapore's diverse soil, the following measures are recommended: Soil Displacement Controls : In sensitive areas, use relief wells pre-boring

at the pile point to reduce ground movement and prevent damage to adjacent structures Course Hero Negative Skin Friction

: If piles penetrate consolidating soft soil, designers must account for long-term downdrag forces

(negative skin friction) by adjusting the required jacking load ( cap P sub j ) during installation Heave Monitoring

: Pile heave must be proactively monitored. If piles heave due to the installation of adjacent piles, their capacity may be compromised, requiring redriving or additional testing BCA Academy Site Stability

: Given the extreme weight of jacking machines (some exceeding 800 tonnes), the working platform must be high-quality, well-compacted, and have excellent site drainage Course Hero Quality Control and Testing All piling works must comply with Eurocode 7 standards and Singapore's national annexes Integrity Testing

: Necessary tests (e.g., PDA, PIT, or sonic logging) must be carried out to verify the structural integrity of the piles Singapore Accreditation Council Permissible Tolerances

: Standard practice allows for an individual pile deviation of up to from its true position Building and Construction Authority Load Testing

Title: GEOSS Good Practice for Installation of Jacked Foundation Piles in Singapore

Document ID: GEOSS-GP-JP-2026 Revision: 1.0 Date: April 2026

1. Introduction

Jacked piles (commonly known as "Jack-in Piles") are a widely used foundation system in Singapore, particularly for residential and commercial projects where noise and vibration must be minimized. Unlike driven piles which use impact, jacked piles are installed by hydraulically pushing the pile into the ground using static force.

Due to past incidents of ground movement, tilting of adjacent structures, and improper termination criteria, the Geotechnical Engineering Society of Singapore (GEOSS) published GEOSS Guide 7. This guide serves as the industry benchmark for "Good Practice" and is referenced by the Building and Construction Authority (BCA).

Step 6: Achieving Set & Termination

2.1. Pre-Installation Ground Truthing

Before the first jacking ram engages, GEOSS mandates a detailed geotechnical site investigation (SI) with boreholes spaced at ≤25m intervals. Crucially, the SI must include:

geoss good practice for installation of jacked foundation piles in singapore