Types of pile foundation || Classification of pile foundation || Classify pile foundation

 Pile foundation can be classified into the following ways as shown in figure :-

• Classification according to Material :-

Concrete Pile :-

Concrete piles may be divided into two basic categories (a) precast piles and (b) cast-in-situ piles. Precast piles can be prepared by using ordinary reinforcement, and they can be square or octagonal in cross section. Reinforcement is provided to enable the pile to resist the bending moment developed during pickup and transportation, the vertical load, and the bending moment caused by a lateral load. The piles are cast to desired lengths and cured before being transported to the work sites.

Some general facts about concrete piles are as follows :-

• Usual length: 10 m to 15 m
• Usual load: 300 kN to 3000 kN 

 Advantages :- 

• Can be subjected to hard driving 
• Corrosion resistant 
• Can be easily combined with a concrete superstructure

Disadvantages :-

• Difficult to achieve proper cut off
• Difficult to transport

Timber Piles :-

Timber piles are tree trunks that have had their branches and bark carefully trimmed off. These are generally circular in shape and diameter varies from 20cm to 50cm. The maximum length of most timber piles is 10 to 20 m. To qualify for use as a pile, the timber should be straight, sound, and without any defects. The bottom is sharpened. There is an iron shoe at bottom and at he top their is a cap.

Advantages :-

• Timber being a resilient material, timber piles are suitable for impact absorption.
• Timber piles are easy to install.
• If necessary, it is easy to uninstall a timber pile.

Disadvantages :-

• These are uneonomical now-a-days.
• They decay due to fungi and insects

Steel Pile :-

Steel piles generally are either pipe piles or rolled steel H-section piles. Pipe piles can be driven into the ground with their ends open or closed. Wide-flange and I-section steel beams can also be used as piles. However, H-section piles are usually preferred because their web and flange thicknesses are equal. In many cases, the pipe piles are filled with concrete after they have been driven. The soil within the pipe is driven out with by compressed air. Then, those pipe are filled with concrete.

Following are some general facts about steel piles :-

• Usual length: 15 m to 60 m 
• Usual load: 300 kN to 1200 kN 

Advantages :-

• Easy to handle with respect to cut off and extension to the desired length. 
• Can stand high driving stresses.
• Can penetrate hard layers such as dense gravel and soft rock d. High load-carrying capacity.

Disadvantages :-

• Relatively costly 
• High level of noise during pile driving 
• Subject to corrosion 
• H-piles may be damaged or deflected from the vertical during driving through hard layers or past major obstructions

Composite Piles :-

The upper and lower portions of composite piles are made of different materials. For example, composite piles may be made of steel and concrete or timber and concrete. Steel-and-concrete piles consist of a lower portion of steel and an upper portion of cast-in-place concrete. This type of pile is used when the length of the pile required for adequate bearing exceeds the capacity of simple cast-in-place concrete piles. Timber-and concrete piles usually consist of a lower portion of timber pile below the permanent water table and an upper portion of concrete. In any case, forming proper joints between two dissimilar materials is difficult, and for that reason, composite piles are not widely used.

Advantages :-

• Their ability to carry relatively high working loads.
• Ability to tend above groundwater level without inherent deterioration.
• suitability in marine installations.

Disadvantages :-

• Difficultly in forming proper joint between two dissimilar materials.

Classification according to Function :-

Bearing Pile :-

These pile are driven upto the hard stratum. They transfer the load of the superstructure to the hard stratum below. These plie virtually act as columns. These pile used to bear vertical loads on their ends.

Friction Pile :-

When the soil is very loose or soft to a considerable depth, friction piles are used. The friction is developed along the surface of the pile by the surrounding soil. The load of the structure is balanced by the friction developed. It is not necessary to drive such pile upto hard bed. Surface of the pile is made rough to increase the skin friction.