Every commercial construction project is unique. Each type of structure will require a foundation specifically engineered to account for the size of the job and the ground on which it’s built. For the same reason, helical pile designs span a variety of shapes and sizes to accommodate a wide range of applications and variables such as soil type, soil profile depths, pile loading type, pile capacity requirements, the type of structure to be supported, etc. There are dozens of sizes, shaft type, and helix configurations available to make sure the proper helical pile is used for the job.
When engineered correctly, a deep foundation anchored with the correct helical pile design will last for many years. Choosing an improper helical pile design can lead to devastating results.
Make sure you choose the proper pile configuration… Call Conte Company Today!
In this brief guide, we’ve outlined the 4 major categories of helical pile designs, including their typical implementations, advantages and disadvantages of each.
Solid Square Shaft
The square shaft is typically solid and capable of large axial compressive loads. The solid shaft is continuous at each extension and carries the load down through to the end of the pile. Square shaft extensions can also used in a variety of tension applications.
Typical Sizes: 1.5”, 1.75”, 2”, 2.25”
Advantages: In rocky and hard soils, square shaft leads are better at advancing without damage.
Disadvantages: Slender shafts do not resist lateral loads well and buckling can occur in soft soils due to the narrower width.
Round Shaft Pipe
The round shaft pipe helical pile provides a much wider diameter than most square shaft piles. The wider cross section provides better structural capacity where large moments, lateral loading, or buckling can be present.
Typical Sizes: 2.875”, 3.5”, 4.5”, 6”, 8”, 10″+
Advantages: Round shaft piles are ideal for softer soils and when there is potential for high lateral loads. The pipe shafts can be grout filled for added structural capacity.
Disadvantages: Larger shafts can be more difficult to penetrate very dense or rocky soils.
Square & Round Shaft Combo Pile
Typically a combo pile has a square shaft lead, followed by round shaft extensions. These types of helical piles are used primarily in compression applications where layers of hard soil are located deep under a softer surface soil. Square/round combo piles are often chosen for high water tables, grout restricted sites or for sites with soils that make them a more economic choice than a grouted pile configuration.
Typical Sizes: 1.5”/2.875”, 1.75”/3.5”, 2.25”/4.5″
Advantages: This combines the better penetrating characteristics of the square shaft with the large diameter round shaft extension to resist buckling and lateral loading.
Disadvantages: Extra material costs can make combo pile solutions a less economical solution than alternative helical piers. It is only necessary under specific circumstances.
Grouted Square Shaft
All square shaft piles can be fitted with accessories to add a grouted casing. This casing is typically 5” to 8” in diameter and can be cased in PVC or steel pipe, or just grout. The grout also creates skin friction with the soil that can help the compression and tension capacity of the pile. The larger cross section improves lateral capacities, bending moment, and buckling resistance strength when compared to the slender square shaft pile on its own.
Advantages: In some soil conditions, square shafts with grout casing are more economical than larger diameter round shaft pipe piles.
Disadvantages: In some cases, grout plates can have difficulty advancing into very dense or rocky soils. Grout may also be prohibited from certain projects, for example in wetland applications or a site which cannot properly accommodate grout-mixing on site.
Choosing the right type of helical pile design needs to be done by an expert!
These basic explanations offer guidelines for which types of helical piles are appropriate for various projects, but there are many variables that go into making an educated decision.