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The parts of a helical pier consist of a helix (coil), shaft, and a support bracket at the top. Variations come with more than one helix, or a shaft made of solid square steel or a pipe section. In the 1830’s, helix screw piles were first introduced as an improvement over the common standard wood pier or driven support pile. Unlike the standard push method, the helix piles were mechanically “screwed” into the ground which increased the bearing load and anchoring properties. Additionally, the helix pier allowed for greater support in muddy or sandy soils.
Nowadays, helical piers provide numerous applications around the world such as stabilizing residential and commercial foundations, supporting hillside abutments, as well as an economical footing for smaller structures such as street lights and flagpoles. They are very versatile and can be installed either vertically, horizontally or diagonally depending on the application. In many hillside support conditions both vertical and diagonal helices are installed and connected together to provide a firm support.
Helical piers are driven into the earth with hydraulic operated rotary drive heads. These drive heads also monitor the torque applied as they screw the pier into the ground. The load factor of each pier is dependent on the size of the pier, along with the number of helices. The underlying soil conditions including type, density, and strata below also play a factor in determining the load.
In terms of foundation repair, the helical pier is driven to a predetermined depth where it sticks firmly into competent strata or bedrock. The bracket at the top of the pier is then attached to the foundation footing for support. In addition to stabilizing, the helical pier can also raise the foundation back to an even level. There are several types of adjustable brackets that attach to the footing which allows for fine-tuning of the elevation. It usually takes a combination of piers to permanently support a foundation built on soil with settlement or other movement issues. When expansive soils are the cause of settlement, helical piers are used to raise or level a foundation.