Helical Piles Explained
Helical piles are a type of deep foundation used on buildings. This type of foundation tends to be favorable for limited access sites that are free of vibrations and other noise. These are fairly easy to install and can easily be removed if the installation runs into a rock layer and needs to be moved. It is not common for these types of deep foundation to be used with large loads as they are much more suited for lower capacity applications such as wind turbines, utility towers and telecom towers.
Laying the Foundation
Helical piles are screwed through many different layers of earth until it hits the bedrock. Which layer the pier is going though is measured by the torque pressure as the different material will create varying amounts of friction. As the pier is screwed into the ground different sections are added. There is no cleanup needed and as long as everything goes to plan it is quite simple and easy to install this type of foundation. It is possible to have multiple piles installed in a matter of hours. If pre-drilling is needed through rock, then it can take several days to insert the piles. Think of these piles like large earth screws. They are made of steel and will be screwed into the ground until they become stable.
One of the main advantages to this type of foundation besides the ease of installation is that these piles will resist all types of upward force. Any force exerted on the piles, even friction, is negligible when compared to the end loading force. This is the building or equipment. Many other types of support will require modification and other filling to counteract these upward forces. Another advantage is that these piles can easily be removed if a rock layer is hit. They can then move the drilling point several feet away. The equipment needed for installation is also small as a skid steer loader and mini excavator can be used. Therefore these piles can be installed in limited access and space areas. It is also possible to use these near ledges and on very steep areas.
One of the main problems with these piles is that different manufacturers will create piles that have different stiffness. This causes the joints weaken under the compression forces. These joints can buckle. It is best to use as stiff as possible piles to start up with. There are shafts and other connections that can be used to strengthen joints but this will take time and money.
Using This System
In order to use helical piles, a professional engineer must come in and approve the plans. The engineer will let you know how many piles are needed and where they should be located. Normally a soil test is needed to determine this. The load that can be supported will depend on the torque. Most common methods will measure torque by measuring hydraulic pressure. An engineer is also handy to have on hand in case something should happen. If the pier needs to be moved then the engineer will be able to determine the best new place for the pier.