Deep foundations are typically used when dealing with cold foundations (foundations allowed to freeze), areas of deep poorly placed fill and/or peat, areas with shallow ground water with poorly placed fill and/or peat, and areas with liquefiable soils. Basically deep foundation are used when it is more cost effective or time effective, depending on the scope of the project, to utilize deep foundations rather than excavate the material that is not suitable for load bearing and replaced with structural fill. The deep foundations transfer the loads from the structure past the shallow soils to deeper soils that are suitable as load bearing.
- Driven Steel Pile - The most common type of deep foundation used is driven steel pipes. Typically these are pipe piles driven with an impact or vibration hammer. Depending on the type of soil that the piles are installed, the bearing capacity is developed from skin friction and/or end bearing.
- Helical Piles – Helical piles are becoming more popular and are an excellent alternative to pipe piles for certain projects. These piles reduce the depth of the foundation and typically require smaller equipment than a pipe pile, therefore they excel in limited construction area, difficult access, and remote areas. Helical piles typically consist of a smaller center shaft (2 – 4 inches in diameter) with large helical bearing plates (6 – 18 inches in diameter) welded to the center shaft. The helical piles are installed using a rotating driving head that rotates the pile using the helical plates to pull the pile into the ground similar to a screw. Most helical piles cannot carry a large lateral load so battered piles are installed to provide the lateral load. We are worked on several projects where custom large center shafts were used with larger helical bearing plates.
- Other (concrete/timber piers, etc.) Some less common types of deep foundation are concrete or timber piers. These types of deep foundations are used on specialty projects or various project constraints require the use. We have designed various types of deep foundations over the entire state of Alaska to suit the project requirements.
