ARTICLE

The Engineer's Guide to Helical Piles in Australia

September 9, 2025

A successful helical pile design integrates structural loads, geotechnical data, and Australian standards to create a safe, durable, and economical foundation.

Helical piles, commonly known in Australia as screw piles, are a modern and efficient deep foundation system.

They are engineered steel piles that are screwed into the ground using hydraulic machinery to provide foundational support for structures.

Their predictable capacity and rapid installation make them an increasingly popular choice for engineers facing tight deadlines and challenging site conditions across Australia.

This guide provides the essential technical information that Australian engineers require to specify, design, and oversee the installation of helical pile systems confidently.

Summary

What They Are: Helical piles, also known as screw piles, are steel deep foundation elements featuring helical plates. They are screwed into the ground to provide structural support.
Why for Engineers: In Australia, they provide a solution for rapid installation, immediate load-bearing capacity, versatility across varied soil conditions, and minimal disturbance to the site.
Key Considerations: Proper design requires a thorough assessment of load capacity, site-specific soil conditions, pile spacing, and strict adherence to Australian Standard AS 2159.
Installation & Verification: The torque applied during installation is a primary indicator of the pile’s capacity. For critical projects, this capacity should be confirmed through on-site load testing.
Cost-Benefit: While the initial material cost might seem higher than traditional concrete options, helical piles often result in significant overall project savings due to reduced time, labour, and equipment needs.

Core Engineering Principles of Helical Piles

Understanding how helical piles function is key to using them correctly. The technology uses proven geotechnical principles to ensure predictable and reliable foundation performance.

How Helical Piles Transfer Load

Helical piles use a dual-action system to transfer structural loads from the building to stable, deeper soil.

End-Bearing: The primary mechanism. The helical plates act like the threads of a screw, directly transferring the load to the competent soil they are embedded in.
Skin Friction: A secondary mechanism. The soil along the pile’s steel shaft provides additional frictional resistance, contributing to its overall capacity.

This system makes helical piles incredibly versatile, allowing them to resist multiple force types:

Compressive Loads: The downward weight of a structure.
Tensile (Uplift) Loads: Upward forces from wind or hydrostatic pressure.
Lateral Loads: Sideways forces.

The Importance of Geotechnical Investigation

A geotechnical investigation is the essential first step for any successful helical pile project. A detailed report from a qualified geotechnical engineer is a requirement, not a recommendation.

It Provides Critical Data: The report is the blueprint for an accurate helical pile design. It identifies:
1. Different soil layers and their depths.
2. Key engineering properties like soil strength and density.
3. Potentially problematic ground conditions, such as soft clay or a high water table.
It Eliminates Guesswork: For an engineer, this information is indispensable. It dictates the pile size, helix configuration, and target depth needed to achieve the required load-bearing capacity.
It Mitigates Risk: Designing a foundation without a geotechnical report is based on assumptions, which introduces unacceptable risk to the project.

Helical Pile Design Considerations for Engineers

A successful helical pile design integrates structural loads, geotechnical data, and Australian standards to create a safe, durable, and economical foundation.

Determining Load-Bearing Capacity

Engineers use a combination of three methods to confidently determine and verify a pile’s load-bearing capacity.

1. Theoretical Analysis: This is the starting point. Using data from the geotechnical report, engineers calculate a preliminary capacity estimate based on soil mechanics principles.
2. Torque Correlation: This is the most widely used method for on-site verification. It relies on the proven relationship between the installation torque (T) and the pile’s ultimate capacity (Qu), expressed by the formula Qu = Kt * T. This provides real-time quality control for every pile installed.
3. Direct Load Testing: Considered the “gold standard,” a physical load test is performed on a pile on-site. This provides definitive proof of the pile’s performance and is typically used for major or critical projects.

Pile Design and Configuration

The physical design of each pile must be tailored to the specific loads and soil conditions of the project.

Shaft Selection: Round shafts are generally preferred for compression, while square shafts offer greater torque capacity and are often used for tension applications.
Helix Configuration: The number, diameter, and spacing of the helical plates are engineered to optimise performance. The goal is to ensure the helices are anchored in a competent, load-bearing soil stratum.
Corrosion Protection: To ensure the foundation’s design life is met, corrosion protection (such as galvanising) is a critical consideration, especially in Australia’s coastal and aggressive soil environments.

Compliance with Australian Standards: AS 2159

In Australia, all helical pile design and installation must comply with a single governing standard.

The Standard: AS 2159-2009 (Piling – Design and Installation) dictates the mandatory requirements for all piling works.
What It Covers: This standard outlines the rules for design actions, required safety factors, material specifications, and testing procedures.
Engineer Sign-Off: A qualified structural or geotechnical engineer must sign off on the final design to certify its compliance with AS 2159, ensuring a safe and high-quality foundation.

The Helical Pile Installation Process: What Engineers Should Monitor

The installation phase is where the design is brought to life. Proper execution is essential for the pile system to perform as intended. Engineers overseeing the project should be aware of the key steps and quality control checks.

Pre-Installation Checks

Before installation begins, a few checks are necessary. The site access must be confirmed to be suitable for the required installation equipment, which is typically an excavator fitted with a hydraulic drive head. The foundation plan must be reviewed, and the pile locations accurately set out on site by a surveyor or a competent contractor. This ensures each pile is installed in its precise design location.

Step-by-Step Installation

The helical pile installation process is systematic and efficient. Engineers on site should observe the following steps:

Positioning: The helical pile is positioned at the set-out location and connected to the hydraulic drive head.
Advancement: The operator applies steady downward pressure, known as ‘crowd’, while rotating the pile. The pile is screwed into the ground, not pushed or vibrated.
Monitoring: Throughout the installation, the operator constantly monitors the pile for verticality and alignment to ensure it stays within specified tolerances.
Torque Reading: A calibrated torque monitoring device provides a continuous, real-time readout of the installation torque. This is the most important data point gathered during installation.
Adding Extensions: If the pile needs to go deeper to reach the target stratum or achieve the required torque, plain steel extensions are coupled to the lead section, and the process continues.
Termination: Once the pile reaches the specified depth and/or final installation torque, the pile is cut to the correct height, and the appropriate structural connection bracket is fitted.

Quality Assurance and On-Site Verification

The supervising engineer plays a key role in on-site quality assurance. This involves observing the work to ensure the contractor is following the specified procedures. A critical part of this is reviewing the detailed installation logs provided by the installer. These logs should record the unique identifier for each pile, its final depth, the final installation torque, and any observations or issues encountered. This documentation forms a permanent record of the foundation installation and confirms that the as-built foundation meets the engineering design requirements.

Foundation Method Comparison

Comparing Helical Piles to Traditional Foundation Methods

This table breaks down the key differences between helical piles, bored concrete piers, and driven piles, helping engineers quickly assess the best option for their project.

Feature	Helical Piles	Concrete Piers/Piles	Driven Piles
Installation Speed	Very Fast. Single-step process with no waiting time.	Slow. Requires multiple steps: excavation, spoil removal, pouring, and curing.	Moderate to Fast. Pile installation is quick, but mobilisation of large equipment can take time.
Site Impact (Noise & Vibration)	Minimal. Low vibration and quiet installation. Ideal for urban or sensitive areas.	Disruptive. Can be noisy during the boring/excavation phase.	Very High. Generates significant ground vibration and loud noise from hammers.
Spoil & Soil Displacement	Virtually None. Screwed into place, causing minimal ground disturbance and generating no spoil.	High Spoil. Generates a large volume of excavated spoil that must be transported and disposed of.	High Displacement. Displaces a large volume of soil as it's hammered in, which can cause ground heave.
Load Readiness	Immediate. The foundation can be loaded as soon as the pile is installed.	Delayed. Requires a lengthy curing period (days or weeks) before it can bear a load.	Immediate. Can typically be loaded soon after installation.
Best Suited For	Restricted access sites, environmentally sensitive areas, projects requiring speed, and sites near existing structures.	Open sites where project timelines are flexible and spoil removal is not a logistical issue.	Open sites far from sensitive structures or urban areas where noise and vibration are not a concern.

Common Applications for Helical Piles in Australian Engineering Projects

The versatility and efficiency of helical piles have led to their adoption across a wide range of engineering projects throughout Australia.

Residential and Commercial Construction

For new foundations, especially on sites with reactive clay or poor soil, helical piles provide a reliable way to bypass problematic upper layers and found the structure on stable ground. They are also an industry-leading solution for foundation repair and underpinning. When an existing building shows signs of settlement, helical piles can be installed to lift and re-level the structure, providing permanent support and preventing further movement.

Infrastructure and Industrial Projects

In the infrastructure sector, helical piles are used to support everything from communication towers and solar panel arrays to regional bridges and boardwalks. Their ability to resist both compressive and tensile loads makes them perfect for structures subject to wind uplift. They are also used for retaining wall tiebacks and to support industrial equipment pads and pipeline infrastructure, often in remote locations where mobilising large concrete equipment would be impractical.

Remote and Environmentally Sensitive Sites

The logistical advantages of helical piles are most apparent on remote Australian sites. The piles and installation equipment are relatively lightweight and can be transported more easily than concrete and its associated machinery. This makes them a cost-effective choice for projects in regional and remote areas. For projects within national parks, coastal zones, or other sensitive ecosystems, the minimal site disturbance offered by helical piles is a key benefit, allowing essential infrastructure to be built with a much smaller environmental footprint.

Summary On What Engineers Need to Know About Helical Piles

For engineers across Australia, helical piles represent a highly reliable, efficient, and versatile deep foundation technology.

They are ideally suited to the continent’s diverse and often challenging ground conditions.

Understanding the core engineering principles behind their design, the importance of a thorough geotechnical investigation, and the critical role of monitoring the installation process is key to success.

When specified and installed correctly in accordance with AS 2159, helical piles provide a cost-effective and robust foundation solution.

Partnering with an experienced helical pile specialist ensures that engineers can leverage the full potential of this technology for their projects.

Frequently Asked Questions About What Engineers Need to Know About Helical Piles

What Are the Disadvantages of Helical Piles?

While highly advantageous, helical piles do have some limitations. Their initial material cost can be higher than that of concrete. They are not suitable for sites with dense rock or ground containing large boulders or cobbles that can obstruct installation. The pile’s capacity is also highly dependent on the skill of the installer, so using experienced operators is essential for a successful outcome.

How Do You Calculate the Capacity of a Helical Pile?

The load-bearing capacity of a helical pile is typically determined using a combination of methods. It begins with a theoretical calculation based on the soil properties from a geotechnical report. This is then verified during installation using the empirical relationship between installation torque and capacity. For critical applications, the capacity is ultimately confirmed with a physical on-site load test.

What Is the Load Capacity of a Helical Pile?

The load capacity of a single helical pile can vary dramatically depending on its design and the ground conditions. Capacities can range from under 10 tonnes for small residential underpinning projects to well over 100 tonnes for large piles used in major commercial or infrastructure works. The capacity is engineered specifically for each project’s requirements.

How Deep Do Helical Piles Need to Go?

Helical piles must be installed to a depth that allows them to penetrate through any weak, unstable, or reactive upper soil layers and anchor into a solid, load-bearing stratum. The required depth is not a fixed number; it is determined by the geotechnical report and is achieved on-site when the pile reaches its specified final installation torque, indicating it is in competent ground.

What Are the Key Design Considerations for Helical Piles?

The key design considerations for a helical pile system include the structural loads it needs to support (compression, tension, and lateral), the detailed geotechnical profile of the site, and the pile’s own configuration (shaft diameter, material thickness, and the number, size, and spacing of helices). Other important factors include the spacing between piles to prevent group interaction and ensuring adequate corrosion protection for the required design life.

Are Helical Piles Up to Code in Australia?

Yes, helical piles are a fully compliant deep foundation system in Australia. When designed by a qualified engineer and installed in accordance with the specifications of AS 2159-2009 (Piling – Design and Installation) and other relevant sections of the National Construction Code (NCC), they meet all Australian standards for safety and performance.