Helical piles, also known as helical piers, screw piles, or helical anchors, are deep foundation systems used to support buildings, bridges, towers, and other structures. They are made of steel shafts with helical plates (or flights) attached to them.
The helical plates resemble a screw, and they are designed to provide the necessary resistance to support the structure.
How helical piles are installed
Helical piles are installed by first drilling a small pilot hole into the ground using a hydraulic motor. Once the pilot hole is drilled to the required depth, the helical pile is then screwed into the soil using a hydraulic torque motor.
As the helical pile is screwed into the ground, the helical plates or flights on the pile create a helix-shaped path in the soil, providing an anchor for the pile. The helical pile is installed to the required depth based on the load-bearing capacity required for the structure it will support.
Once the pile is installed to the required depth, the pile is connected to the foundation of the structure using a bracket or other connection method. The process is repeated for each helical pile required to support the structure.
Types of helical piles
- Standard helical pile
- Round shaft helical pile
- Square shaft helical pile
- Helical pulldown micropile
- Helical mini pile
- Grouted helical pile
- High-capacity helical pile
- Helical tension pile
- Helical compression pile
- Soil screw pile
1. Standard helical pile
A standard helical pile consists of one or more helical-shaped plates (or “blades”) that are welded to a central shaft. The plates are rotated into the soil using hydraulic machinery, and the weight of the structure is transferred to the soil through the helical plates.
2. Round shaft helical pile
A round shaft helical pile is similar to a standard helical pile, but the central shaft is round instead of square. Round shaft helical piles are typically used in smaller-diameter applications and in soil conditions where torque resistance is not a primary concern.
3. Square shaft helical pile
A square shaft helical pile has a central shaft that is square in shape. This type of pile is commonly used in applications where high torque resistance is required, such as in expansive soils or in seismic zones.
4. Helical pulldown micropile
A helical pulldown micropile is a small-diameter pile that is used in situations where a high-capacity foundation is needed in soil conditions that are not suitable for standard helical piles.
The pile consists of a central steel shaft with one or more helical plates that are screwed into the ground. Once the pile is in place, grout is injected into the shaft to provide additional support.
5. Helical mini pile
A helical mini pile is a small-diameter pile that is commonly used in situations where access is limited or where minimal soil disturbance is required. The pile consists of a central steel shaft with one or more helical plates that are screwed into the ground.
The piles are typically installed using handheld equipment and are commonly used in residential or light commercial applications.
6. Grouted helical pile
A grouted helical pile is a standard helical pile that is installed with a casing to prevent soil disturbance during installation. Once the pile is in place, grout is injected into the casing to provide additional support and to fill any voids around the pile.
Grouted helical piles are commonly used in situations where high-capacity support is required or where soil conditions are variable.
7. High-capacity helical pile
A high-capacity helical pile is designed to support heavier loads than standard helical piles. The pile consists of a central steel shaft with one or more helical plates that are screwed into the ground. The diameter and thickness of the shaft and plates are increased to provide additional support and capacity.
8. Helical tension pile
A helical tension pile is used to resist uplift or tension forces, such as in retaining walls or guy anchors. The pile consists of a central steel shaft with one or more helical plates that are screwed into the ground.
The tension forces are transferred to the pile through a connection at the top of the pile.
9. Helical compression pile
A helical compression pile is used to resist downward or compression forces, such as in building foundations or bridge abutments. The pile consists of a central steel shaft with one or more helical plates that are screwed into the ground.
The weight of the structure is transferred to the pile through a connection at the top of the pile.
10. Soil screw pile
A soil screw pile is a type of helical pile that is commonly used in temporary structures or for soil stabilization. The pile consists of a central steel shaft with one or more helical plates that are screwed into the ground.
The piles can be easily installed and removed and are commonly used in applications such as tent anchors, temporary fences, or erosion control.
How helical piles work
Helical piles work by using helix-shaped plates or flights to screw into the ground and provide support for a structure.
The helical plates on the pile create a path through the soil, which provides an anchor for the pile. The load capacity of the helical pile is determined by the depth of the pile, the diameter of the helix, and the number of helixes on the pile.
When a structure is built on top of the helical pile, the weight of the structure is transferred to the pile, which in turn transfers the weight to the soil. The helical pile uses the surrounding soil to provide additional support and stability for the structure.
Because of their unique design, helical piles can be used in a variety of soil conditions and can be installed quickly and easily without the need for excavation or concrete.
Minimum concrete grade use for pile
As per the Indian standard code IS 2911-2010, Part 1 clause 7.3.3 a minimum concrete grade of M25 (which means a minimum compressive strength of 25 N/mm² after 28 days)) is used for pile construction.
Advantages of helical piles
1. Cost-effective
These piles can be installed more quickly and at a lower cost compared to traditional foundation systems. There is also no need for excavation or curing time for concrete.
2. Versatile
These piles can be installed in a wide range of soil conditions and can support a variety of structures, including residential, commercial, and industrial buildings.
3. Minimal site disturbance
Since these piles are installed using small, specialized equipment, there is minimal disturbance to the site during installation. This is particularly useful in areas where there is limited access or space.
4. High load capacity
These piles can support heavy loads and can be designed to accommodate specific load requirements.
5. Immediate load transfer
Helical piles provide immediate load transfer and can be used to support structures right after installation.
6. Environmentally friendly
These piles do not require excavation, and they can be easily removed, leaving minimal impact on the environment.
7. Reduced vibration
The installation process for helical piles produces minimal vibration, making them an ideal solution for sites where vibration is a concern.
Disadvantages of helical piles
1. Site-specific design requirements
These piles require careful consideration of soil conditions and other site-specific factors to ensure that they are designed to properly support the structure.
2. Not suitable for all soil conditions
While these piles can be used in a wide range of soil conditions, they may not be appropriate for certain types of soil, such as highly organic soils or soils with a high water table.
3. Installation can be impacted by obstructions
These piles rely on being able to screw into the soil, and if there are large rocks or other obstructions in the way, the installation process can be slowed or even halted.
FAQ
What are helical piles?
These are deep foundation elements used to support structures by transferring the load of the structure to deeper, more stable soil layers.
How are helical piles installed?
These piles are installed by rotating a steel shaft with helical plates into the soil. The pile is screwed into the ground until it reaches a suitable depth and the required capacity is achieved.
What are the advantages of helical piles?
The advantages of helical piles include ease of installation, high load capacity, minimal site disturbance, ability to be installed in various soil conditions, and immediate loading capabilities.
What types of structures can helical piles support?
These piles can support various types of structures including residential and commercial buildings, bridges, communication towers, and foundation repairs.
