Deep foundation belongs to the structural elements which deliver loads via poor, compressible soils to the elementary competent soils or rock. As per the term of civil construction, deep foundations stand for the piles, piers, drilled shafts, and caissons which are built in deep into the ground. Under deep foundation the depth to width proportion generally remains in excess of 4 to 5. Deep foundations disperse the load of the super structure vertically instead of laterally done by shallow foundations. Deep foundations are arranged as soon as the predictable loads from superstructure fail to be supported with shallow foundations.

Deep foundation is set up in the following conditions:-

• The strata according good bearing strength is not obtainable adjacent to the ground.
• The space is confined to provide for spread footings.

Under these conditions, the foundation of the structure should be constructed intensely to achieve a bearing stratum that is acceptable and maintains durability and consistency of a structure efficiently.

Besides, bearing stratum, there are also other cases. As for instance, the foundation for a bridge pier should be arranged under the scour depth, even though appropriate bearing stratum may prevail at a greater level.

Deep Foundation is categorized as follow: -

• The piles
• The pile caps

Piles stand for long and narrow members. The purpose of these members is to deliver the load to depth soil or rock having high bearing strength to circumvent shallow soil with low bearing strength.

Pile caps belong to solid slabs which are applied to attach a group of piles jointly to support and transfer column loads to the piles.

Application of Pile Foundations: -

• Stratum of necessary bearing strength remains at higher depth
• Steep slopes are present
• Compressible soil or water-logged soil or soil of made-up type

Illustrations: Piles are useful for making basement of buildings, trestle-bridges and water front installations (piers, docks etc).

On the basis of function, the piles are categorized as follow:-

1. End Bearing Piles
2. Skin Friction Piles
3. Compaction Piles
4. Driven Piles
5. Auger cast Piles

Well Foundation: -

It has similarity with deep foundations. The main variation among a well and a pile foundation is that a pile is compliant like a beam against horizontal loads, whereas the well experiences inflexible body movement against such loads.

On the basis of different types of shapes, the well foundation is categorized as follow:-

• Circular Wells
• Dumb bell
• Double-D Wells
• Double Octagonal Wells
• Single and Double Rectangular Wells
• Multiple Dredged Holed Wells