Square Shaft Helical Anchor
Square shaft helical anchors are used in construction to provide extra support to the structure by stabilizing the foundation. In constructions where the site is on poor soil conditions such as rocky areas, square shaft helicals can be used to add tensile strength to the foundation, making the structure more stable.
Poor ground conditions such as rocky or dense soils can make it difficult for the foundation to support the structure since weight is not distributed evenly. To mitigate this and other damages to foundation, square shaft anchors are used to increase the stability of the foundation by helping to increase its strength without causing damage to the ground.
The design of the square shaft helicals is made up of helices with tapered blades attached to a square shaft anchor. This design enables the helicals to penetrate the ground easily even in dense and rocky soils.
Square shaft helical anchors tend to have a smaller diameter compared to round shaft helicals so they are better suited to dense hard to penetrate soils. They are also an excellent option for strengthening foundations where additional tensile strength is required.
Square Shaft Helical Anchor Drawing
| Shaft Size | Installation Torque Factor (k) | Axial Compression Load Limit | Ultimate-Limit Tension Strength | Useable Torsional Strength |
| 1-1/2” Square Bar | 9 – 11 | 70,000 lb. | 70,000 lb. | 7,500 ft-lb |
| 1-3/4” Square Bar | 9 – 11 | 100,000 lb. | 100,000 lb. | 11,000 ft-lb |
| 2-1/4” Square Bar | 10 – 12 | 200,000 lb. | 200,000 lb. | 23,000 ft-lb |
| 2-7/8” Tubular – 0.203” Wall | 8 – 9 | 60,000 lb. | 60,000 lb. | 5,500 ft-lb |
| 2-7/8” Tubular – 0.262” Wall | 8 – 9 | 100,000 lb. | 100,000 lb. | 9,500 ft-lb |
| 3-1/2” Tubular – 0.300” Wall | 7 – 8 | 115,000 lb. | 120,000 lb. | 13,000 ft-lb |
| 4-1/2” Tubular – 0.337” Wall | 6 – 7 | 160,000 lb. | 160,000 lb. | 22,000 ft-lb |
Applications of Square Shaft Helical Anchors
In construction projects where there is need for extra tensile strength and torque capacity to stabilize the foundation, square shaft helical anchors are ideal. They are commonly used in applications such as
They can be used in:
- Construction of new foundations including tower foundations, bridge foundations and industrial equipment foundations.
- Projects that require soil stabilization
- Correcting and repairing damaged foundations.
- Correcting and straightening walls.
How to Install Square Shaft Helical Anchors?
Square shaft helicals are made to be used even in conditions with limited access and mobility. Their installation does not require excavation or heavy duty equipment. Since the helicals are designed more or less like a corkscrew, they can be screwed into the ground with minimal damage to the surface.
The square shaft shaft of this type of helical anchor gives it a small diameter that is ideal for penetrating dense and rocky soils with ease. They can also be installed in any season and are ideal for soils where the water table is high.
During installation the square shaft helicals are spread out evenly on the ground in order to achieve the desired load capacity. This creates a strong and durable foundation that can withstand the load of the structure without getting damaged.
For tilt up constructions, new and damaged foundation projects, as well as industrial applications, square shaft helical anchors are a cost effective solution that helps to minimize labor costs and installation time.
Advantages of Square Shaft Helical Anchors
- Ideal for dense, rocky and hard soils.
- Quick and easy installation in all seasons.
- Suitable for constructions on sites with active soils and those with a high water table.
- No curing time required.
- Minimal disturbance to the soil.
- No extensive excavation required for installation.
- Available in galvanized options for corrosion resistance and long-term performance.
- Able to support large axial compressive loads.
- Easy to uninstall and reinstall in a different position incase of obstructions like boulders.
- Offers predictable performance since the relationship between installation torque and capacity is empirical
Frequently Asked Questions
How do square shaft helical anchors work?
Square shaft helical anchors help to increase the stability of foundations by increasing the tensional resistance of the foundation. When they are installed into the ground they help to spread the tensional force of the structure increasing resistance to lateral forces and preventing soil movement.
Are square shaft helicals different from round shaft anchors?
Yes, square shaft helicals are structurally different from round shaft helicals. They have a square shaped shaft to which the tapered helical blades are attached. The square shaft cross section gives them a smaller diameter compared to round shaft helicals. They are also more suited to uplift or tension force applications while round shaft helicals are ideal for compression or downward forces.
How are square shaft helical anchors installed?
Square shaft helicals are installed by screwing or threading into the ground. They can be installed with hydraulic equipment and do not require any excavation or predrilling to be installed. They cause minimal soil disturbance and can easily penetrate dense and rocky soils.
Why use square shaft helical anchors?
Compared to traditional deep foundations, square helicals are easy to install, cost effective and less disruptive to the ground. They also offer more versatility in terms of installation in poor soil conditions such as rocky or very dense soils. The ease of installation also means that they can be used in areas with limited access and mobility.