Pile Foundation: Pile foundation is a type of building foundation that has a depth more than its width. These types of foundations finds its utilisation in those area where the foundation beneath the ground level has to transfer a heavy and huge amount of loads into the sub- soil but there is an absence of proper strata of soil which can bear the loads of the building without being dismantle. Sometime the pile foundation is used in the place of raft foundation when the loading is uneven and load bearing strata does not exist at a shallow depth.
The basic concept of pile foundation is very simple but the format of pile foundation is changing over the years. In these types of building foundation, a pile is inserted into ground till satisfied soil strata is not reached or the required amount of strength is not gained by the foundation in the course of its insertion so that it can withstand against the desired standard. Piles are structural components that are made of steel, concrete, or timber. The use of pile foundation is more costly than compared to other foundation but often it becomes necessary to give greater priority to structural safety over cost expense.
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Types of piles and their characteristics in building foundation :
The types of piles used in constructional works are different and their usability varies depending upon the types of load to be carried by the pile, the sub-soil condition, and the location of water table. Piles can be classified into the following groups:
Classification of Pile foundation on the basis of function :
- End bearing pile: These are used to transfer heavy load through soft-soil to suitable hard strata. Tall buildings with heavy load are provided with these types of foundation. Multi-story buildings with soft sub soil are mostly built on end bearing pile foundation.
- Friction pile: In these types of piling the load of a building is transferred to the soil by means of producing skin friction with the help of friction producing material. The foundation is so done that the material used for foundation produces maximum frictional force so that it can work under any condition. Such types of piling are used in the areas where granular soil exists.
- Combined end bearing and friction pile: This is a combination of both end bearing and frictional piling. These types of piles are also preferred in those areas where there exists a granular sub –soil.
- Compaction pile: Compaction pile foundations are those kinds of foundation where the pile do not carry any load but it generally compact the soil of the strata. The piling material used in piling can be weak material like wood, timber etc.
Classification of Pile foundation on the basis of materials used :
- Steel pile: steel foundation is generally either pile piles or rolled steel H section piles. In steel piling steel pipes are used which are driven into the ground with their ends open or closed.
- Concrete pile: Concrete piles are made up of concrete. Different types of concrete piles are made for different conditions depending upon the maximum design load of the structure.
- Timber pile: Timber foundation is made up of tree trunks. For a sound working of timber foundation there are some requirements which are to be fulfilled by these timber pile foundation. These requirements are as follows: (a) the timber should be free from bends, knots, shakes, decays and splits ;(b) the timber should be free from short or reverse of bends and from crooks greater than one-half of the diameter of the pile at the middle of the bend; (c) there should be straight line between corners of the butt and the tip within the body of the pile; (d) there should be uniform tapper from butt to tip.
- Composite pile: Composite piles are the combination of two different materials. These piles are made by driving one material above the other. Timber-concrete composite pile and steel-concrete composite pile are the two most common types of composite piles used.