Building Strong Foundations: A Deep Dive into Screw Pile Installation
- DownForce Piling
- Sep 9
- 5 min read
When it comes to constructing durable and reliable foundations, screw piles (also known as helical piles) offer a superior choice. Whether you're a builder, contractor, or homeowner in Calgary, understanding how these innovative foundations are installed and their numerous advantages can help you ensure lasting success for your projects.
The Efficient Process of Screw Pile Installation
Screw pile installation is designed to be quick, efficient, and minimally disruptive, providing a solid foundation with advanced equipment and expertise.
Site Preparation and Layout: Before any piles go into the ground, the project site is carefully marked out. This includes defining the perimeter of the structure and precisely locating each pile. A rotary laser level is used to set the exact height of the pile saddles, which ensures fast and accurate beam installation later on. Little to no ground preparation is typically required, minimizing disturbed earth.
Equipment and Assembly: Screw piles are installed using specialized equipment, often a hydraulic drive head mounted on a skid steer loader, excavator, or backhoe. For smaller projects, a grass track mini Kubota excavator with a custom auger attachment can be used. The drive head, sometimes called an auger, is powered by the excavator's boom. A "bale piece" connects the drive head to the boom, suitable for new construction or underpinning, allowing the pile to go straight down. Other attachments like a "yoke" are used for tie-backs in shoring jobs, such as for seawalls or highways, drilling at an angle.
Beginning the Installation (Lead Section): The helical pile, which looks like a large screw or auger but is fundamentally different as it doesn't cause spoils or vibrations, is inserted into the boom. The excavator operator applies downward "crowd pressure" while the pile begins to rotate. It's crucial for the ground crew to assist the operator in keeping the installation plumb (straight up and down), especially during the installation of the lead section and the first plain extension. This ensures proper alignment and effectiveness.
Extending the Pile to Depth: After the lead section is installed, plain extensions are added to reach the appropriate depth. Extensions with additional helical plates are also available if more torque and, consequently, more load capacity are needed. The connection between pieces is a forged male-female connection secured with a single through-bolt. A 12-inch or larger crescent wrench is used to tighten these bolts, and connections should be double-checked for positive engagement.
Monitoring Installation Torque (The Key to Capacity): Accurately measuring the installation torque is the single most important aspect of the process. The installation torque has a direct relationship to the pile's load capacity, similar to how driving force relates to a driven pile. Modern devices, such as the CHANCE® digital torque indicator, directly measure torque using strain gauges, eliminating the accuracy problems of older methods that estimated torque from hydraulic pressure. These devices are durable, have no moving parts, and allow contractors to read the exact foot-pounds of torque at every step, which engineers highly value. For square shaft material, a KT value of 10 means 1,000 foot-pounds of torque is equivalent to 10 Kips (10,000 pounds) of capacity. For example, a 1.0 reading on the indicator can mean 1,000 foot-pounds of torque, equating to 10 Kips for that material.
Optimal Installation Speed: Helical piles should be installed at operating speeds between 8 and 16 RPMs. Installing them faster can "auger" a hole, which negatively impacts the pile's load capacity. The pitch on each helical plate is 3 inches, so if the pile is advancing correctly, it should advance approximately 3 inches per revolution.
Addressing Challenges: If a pile is "spinning out" (not advancing properly, like stripping a screw), the solution typically involves applying more crowd pressure or adding more and/or larger helical plates to generate increased downward thrust. It's also normal to see a permanent twist or wrap in the steel shaft when approaching the maximum torque capacity of the material, which serves as a good visual indicator of installation torque without damaging the shaft. However, it is not recommended to exceed the maximum torque capacity, as this can cause a clean break below ground.
Completing the Foundation: Once the required torque and depth are achieved, the installation is complete. The pile cap assembly, consisting of a threaded rod, a saddle, and an adjustment nut, sits on top of the pile. This pile cap can be easily adjusted by twisting the saddle or adjusting the nut, ensuring a level and ready-to-build foundation.
Advantages of Screw Piles for Calgary Projects
Screw piles offer numerous benefits that make them an excellent choice for a wide range of applications in Calgary:
Speed and Efficiency: Screw piles are relatively quick to install and require little or no ground preparation, leading to minimal disruption on site. For example, Down Force Piling and Supply highlights their efficient and reliable process, ensuring solid foundations quickly.
Superior Reliability and Durability: Originally designed for lighthouses in the 1800s to prevent them from falling into the ocean, this technology has proven its longevity, with some of the oldest lighthouses still standing on similar foundations. One professional reported zero failures in 40 years of installing these foundations, often exceeding city inspection requirements.
High Load Capacity: Screw piles can achieve significant load capacities. For instance, an inch and three-quarter square shaft material can be good for 10,500 foot-pounds, equating to 100 Kips or 100,000 pounds.
Environmental Friendliness: Unlike augers that drill holes and cause spoils (excavated earth), screw piles work like a screw into wood, creating no spoils and no vibrations. This minimal disturbance to the ground is a significant environmental advantage.
Versatility: Screw piles are suitable for various applications, including new construction, foundation lifts, underpinning existing structures, and even tie-back anchors for shoring jobs like seawalls and highways.
Engineered for Success in Calgary: Companies like Down Force Piling and Supply, a trusted, family-owned business in Calgary, engineer all jobs to ensure the correct pile size for each project, with this design work included in the pile price. They also offer on-site custom welding to meet unique project requirements.
Proven Trust: Down Force Piling and Supply is trusted by Calgary's top home builders, showcasing their reputation for quality and service within the local community. They also demonstrate commitment to the local community through their 4-C's program, donating 1% of revenue from core clients to charities.
Adaptability to Soil Conditions: The installation process accounts for varying soil conditions, from softer to very dense soils like caliche. The ability to monitor torque in real-time ensures the pile reaches adequate bearing capacity even in challenging ground.
By leveraging advanced equipment and expert installation techniques, Calgary's construction projects can benefit immensely from the strength, efficiency, and environmental advantages that screw piles provide.