Pile foundations are a type of deep foundation. They are adopted when firm ground strata are not available at shallow depth or load coming from superstructure is excessive.
Pile foundations could be classified in many different ways.
- Classification based on function
- Classification based on material and composition
Classification based on function
- End bearing pile foundations
This type of piles transfers load coming from the superstructure, directly to the firm and hard ground. They are suitable when there is firm ground strata is available at comparatively shallow depth.
- Friction piles
Friction piles used in case of footing in cohesive soil. If hard strata are available at greater depth, friction piles are chosen. Friction piles transfer load to the ground by friction between skin of pile and ground.
- Compaction piles
Compaction piles are so designed that they have very less strength. They do not carry any direct load, but they are used to compact loose granular sands. And thus, increasing the bearing capacity of soil.
- Anchor piles
- Fender piles and dolphins
These are used to protect water front structures against the impact from ships or floating objects.
These are well known for resisting uplift force and over-turning moment cause by hydrostatic pressure.
Classification based on material and composition
- Concrete piles
- Precast prestressed piles
- Cast in situ piles
- Timber piles
- Steel piles
- Composite piles
- Concrete and timber
- Concrete and steel
- Underreamed piles
Nagative Skin Friction Acting On Piles
It is caused by the settlement of loose soil surrounding the soil that adds downward force on the pile. Negative skin friction is an unwanted phenomenon as it decreases the bearing capacity of the pile.