Helical Piers: Design, Applications, and Field Performance

An Atlas Foundation Podcast Breakdown

Helical piers have become an increasingly common deep foundation solution for projects where site constraints, soil conditions, or installation requirements make traditional foundation systems less practical. Their ability to be installed quickly with minimal vibration and immediate load capacity makes them particularly useful for both new construction and existing structures.

In a recent episode of the Atlas Foundation Company podcast, we discussed the engineering principles behind helical piers, where they are commonly used, what engineers should consider during design, and what happens when those designs reach the field.

Where Are Helical Piers Used?

Helical piers are versatile, but they aren't the right solution for every project. Understanding the structure, anticipated loads, subsurface conditions, and site constraints is critical when determining whether they are appropriate.

Common applications include:

• Commercial and light commercial structures

• Residential foundations

• Equipment foundations

• Additions to existing buildings

• Boardwalks and decks

• Underpinning and foundation repair

• Projects with limited site access

One of the biggest advantages of a helical system is the relatively small installation equipment required compared with many conventional deep foundation systems.

On sites with limited overhead clearance or restricted access, smaller installation equipment can provide options that would otherwise be difficult to achieve with larger pile-driving equipment.

Low vibration also makes helical piers particularly valuable for work around existing structures.

Designing a Helical Pier System

Successful helical pier installation starts well before equipment arrives on site.

The design process requires engineers to evaluate the anticipated structural loads alongside the site's geotechnical conditions. Soft clays, loose sands, uncontrolled fill, and varying soil profiles can all influence the selection and design of a deep foundation system.

Helical piers can be designed to resist several types of loading, including:

Compression: Loads transferred downward from the structure into suitable bearing soils.

Tension: Uplift forces resisted through the helical bearing plates and surrounding soil.

Lateral: Horizontal forces that require consideration of both the pile configuration and surrounding soil conditions.

The configuration of the helical pile itself is another important part of the design. Engineers may evaluate factors including shaft size, helix diameter, number of helices, helix spacing, and required embedment depth.

Ultimately, the goal is not simply to install a pile to a predetermined depth. The foundation needs to achieve the capacity required by the design.

Installation Torque and Capacity

One of the unique characteristics of helical pier systems is the relationship between installation torque and pile capacity.

During installation, torque is continuously monitored as the pier advances into the soil. The measured installation torque provides valuable information about the soil resistance encountered by the pile and can be correlated with the anticipated capacity of the installed pier.

This gives the installation team real-time information from the field.

Rather than relying solely on an assumed installation depth, torque measurements can help verify that the pile has reached conditions capable of supporting the required design loads.

However, torque correlation is not a substitute for proper engineering. Soil conditions, shaft configuration, pile geometry, installation equipment, and applicable design criteria all need to be considered when evaluating capacity.

What Happens During Installation?

Helical piers are typically installed using hydraulic equipment that applies rotational force to the pile shaft.

The lead section containing the helical plates is advanced first. As greater depths are required, extension shafts are added until the pier reaches its required installation criteria.

Throughout this process, the installer monitors several factors, including:

• Installation torque

• Depth

• Alignment

• Verticality

• Changes in soil resistance

Field conditions do not always match expectations perfectly.

Variable soil layers, buried obstructions, dense materials, or unexpected refusal can affect installation. This is where communication between the geotechnical engineer, structural engineer, contractor, and foundation installer becomes particularly valuable.

The drawings may establish the design intent, but field data helps determine how that design performs in actual subsurface conditions.

Advantages of Helical Piers

When site and soil conditions are appropriate, helical piers can provide several practical advantages.

Installation is typically fast, and unlike concrete foundation elements, helical piers do not require curing time before they can carry load. Once the required installation criteria are achieved and the system is properly connected, the foundation can provide immediate load capacity.

Other advantages include minimal vibration, relatively low installation noise, smaller equipment requirements, and the ability to work in areas where access may be difficult for conventional deep foundation equipment.

These characteristics can make helical piers especially useful for renovation, underpinning, additions, and projects immediately adjacent to existing structures.

Understanding the Limitations

The benefits of helical piers are significant, but understanding their limitations is equally important.

Dense gravels, cobbles, obstructions, and very hard soil conditions can make advancement difficult or prevent the helices from reaching the intended bearing layer. Certain projects may also require capacities that make another deep foundation system more appropriate.

Corrosion and long-term durability must also be evaluated based on the anticipated service life and site conditions.

A helical pier should not be selected simply because it can be installed quickly. The system has to make sense for the loads, geology, access, constructability, and long-term performance requirements of the project.

Bringing Design and Field Performance Together

One of the most valuable aspects of helical pier installation is the information gathered during construction.

Installation torque, depth, soil resistance, and field observations provide feedback about the conditions encountered below grade. When those observations align with the geotechnical information and design assumptions, they provide another layer of confidence in the installed foundation system.

When conditions differ, having experienced engineers and installers involved allows the project team to respond appropriately.

That collaboration is especially important in foundation work, where subsurface conditions cannot always be completely characterized before construction begins.

Is a Helical Pier System Right for Your Project?

There is no single deep foundation system that is right for every site.

Helical piers can be an effective solution when a project requires rapid installation, minimal vibration, limited-access equipment, or a foundation capable of carrying load immediately after installation. However, successful performance depends on selecting and designing the system around the actual structural and geotechnical conditions of the project.

At Atlas Foundation Company, our experience with helical systems goes back decades. By working with engineers, contractors, and project teams early in the process, we can help evaluate foundation options and identify potential constructability considerations before they become field problems.

Want to hear the full discussion? Watch Helical Piers: Design, Applications, and Field Performance on the Atlas Foundation podcast.

Have a project where helical piers may be an option? Contact Atlas Foundation Company to discuss the site conditions, loading requirements, and foundation solutions available for your project.