Foundation | What is Deep foundation
A deep foundation is those in which the depth of the foundation is very large in comparison to its width.
A deep foundation may be of the following types:
- Pile foundation
- Caissons or
- Well foundation
Pile Foundation is the type of foundation in which the loads are taken to a low level utilizing vertical members which may be timber, concrete or steel.
So pile foundation may do adopted when no firm bearing seams are available including the loading is uneven.
- End bearing piles:- These types of piles are used to transfer load through water or soft soil to a suitable bearing stratum.
- Friction Pile: Friction piles are used to transfer loads to a depth of friction load-carrying material using skin friction along the length of the pile.
- Compaction pile: Compaction piles stand used to compact loose granular soils thus increasing their bearing capacity.
- Batter Pile: Piles that are driven at an inclination to resist large horizontal or inclined forces.
- Fender Pile: These piles are used to protect the waterfront structure from the impact that may be caused by ships.
- Sheet Piles: Sheet piles are used for retaining soil that is liable to escape laterally when subjected to pressure or to enclose the area required for some foundation and protect it from the action of running water or leakage.
Cofferdam in Deep Foundation
- It is a temporary structure constructed in a river or lake or any other water-bearing surface for excluding water from a given site to enable the building operation to be performed on a dry surface.
- Earthan Cofferdam: It essentially consists of an earthen embankment built around the area to be enclosed. It is constructed where the depth of water is not much (1.3 to 1.8 m)& the velocity of the current is very low.
- Rockfill Cofferdam: The depth of water to be retained by the embankment of the cofferdam is an order of 1.8 to 3m, stone or rubble is used for the embankment.
- Crib Cofferdam: In deep water wherever it is challenging to penetrate the guide piles or sheet piles within the hard bed below, crib cofferdam is used. In this type of cofferdam, the sheet piles are underpinned through a series of wooden cribs.
Cellular Cofferdam in Deep Foundation
- This type of cofferdam is mostly used for dewatering large areas in places where the depth of water may be of the order of 18 to 21 m. the acellular cofferdam is made by driving a straight web steel sheet pile, arranged to form a series of interconnected cells. Ultimately, the cells are filled with clay sand or gravel to obtain them stable.
The two common shapes are Deep foundation
- Circular-type cellular cofferdam
- Diaphragm-type cellular cofferdam