A deep foundation is a type of foundation distinguished from shallow foundations by the depth they are embedded into the ground.
There are many reasons why a geotechnical engineer would recommend a deep foundation over a shallow foundation, but some of the common reasons are:
- very large design loads,
- poor soil at shallow depth,
- or site constraints (like property lines).
This kind of foundation has the advantage to prevent sinking in the long-term, as they exploit the resistance (both on account of friction and leaning) of deeper and suitably bearing layers of soil, bypassing unsuitable grounds.
Concrete piles are typically made with steel reinforcing and prestressing tendons to obtain the tensile strength required, to survive handling and driving, and to provide sufficient bending resistance.
The pole must have a suitable reinforcement set to resist all strains generated by lifting, handling, impact driving and by the static load it has to support.
Pile joints can be used with both precast and pre-stressed concrete piles, to join two or more short piles to form one long pole.
The pile section is typically solid and square, hexagonal or sometimes octagonal.
Hollow round sections is used with spun poles. This type of poles are usually tapered.
Elements in this category can be produced in the desired length at a dedicated workshop, left out for curing and then delivered to the jobsite.