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How to choose type of pile foundation?
The types of pile along with their advantages and disadvantages and applications can be used to guide designer to choose the most appropriate type of pile for the given condition:- Driven pile
- Driven and cast in place pile
- Bored and cast in place pile
Fig.1: Selection of types of pile foundations
Driven Pile
To be able to select driven pile for any project, the applications, advantages, and disadvantages that such type of pile may offer should be known. The most outstanding advantages of driven piles involves considerably long piles can be installed and it can be carried out specifically in marine structures. Moreover, it has sufficient stability in squeeze ground, it is not affected by ground heave while neighboring piles are placed, the pile material can be examined and inspected before it is forced into the ground, and ground water does not influence the construction of driven piles. As far as disadvantages of driven piles are concerned, strong driven might cause unobserved damages and possible severe deterioration that not only extend construction schedule but also increase construction cost. Furthermore, driven piles cannot be installed in low headroom condition, end enlargement are not always beneficial, and vibrations and noises due to driving process could lead to damages. Lastly, it is not cost effective when the amount of material in the pile is controlled by driving stress instead to permanent load stresses.
Fig.2: Driven Pile Foundation
Driven and Cast-in-Place Pile
Similar to driven piles, it is necessary to outline and explain pros and cons of driven cast in place pile along with its applications. The advantages of this type of pile involves construction of enlarged base form in certain types of driven and cast in place pile, the effect of ground water can be avoided due to a closed end tube that driven into the ground, and noises and vibrations of certain types of driven and cast in place pile could be reduced. Another advantage is that the length of this type of pile can be changed according to the level of bearing stratum and driven or handling stress would not affect materials in the pile. Regarding disadvantages of driven and cast in place pile, the length of the pile cannot be varied, and it might suffer waisting and necking in squeezing ground except if special considerations are practiced during concreting. Moreover, structures at the vicinity of construction area are possible to experience damages and deterioration due to vibrations and noises that generated during construction. Furthermore, it is neither suitable for substantially low head room condition nor it can be considered in the marine structure or in river unless special adaptation is considered. Finally, ground displacement due to driven of pile could lead to adjacent green concrete damages, and it is not possible to examine concrete after the completion of construction process.
Fig.3: Construction of driven and cast in situ pile
Bored and Cast-in-Place Pile
This type of pile foundation offers several advantages for instance considerably long pile can be installed, it can be driven in low head room situation, and large diameter piles can be utilized. Moreover, soil that taken out from borings during construction can be inspected, sampled, or tested. Not only does the length of bored and cast in place pile can be changed to accommodate ground conditions but also it can be installed without generating much vibration and noise. Regarding disadvantages of bored and cast in place pile, it is prone to necking in squeezing land, poured concrete can be examined, and enlarged end piles cannot be constructed unless special approached are employed. Finally, washing out of cement due to water which is under artesian pressure, sinking piles in cohesionless soil could cause the settlement of neighboring buildings, and sandy soil and gravelly soil may be loosen and consequently the base of the pile should be grouted to stabilize the base of the pile.
Fig.4: Bored and cast in place pile
How to choose type of pile in the same pile category?
After the type of pile has been determined, it is necessary choose suitable type of pile (timber, steel, concrete) in that pile category that has been selected. There are various types and forms of piles in each three major piles. Guideline for the selection of pile type in each category are discussed.- Driven pile
- Driven and cast in place pile
- Bored and cast in place pile
Selection of Driven Pile
Driven piles can be constructed from timber, concrete, or steel. Table-1 can be used as a guideline to choose an appropriate type of driven pile. Table-1: Selection of driven pile type based on their advantages and disadvantages and construction conditions| Types of driven pile | Suitable condition | Unsuitable condition |
| Timber driven pile | Suitable option for temporary works or when the load is small | Cannot be used when loads are large. It may suffer decaying if water level fluctuates, and it is not suitable for heavy driven since it may experience unseen splitting. |
| Concrete driven pile | Extra reinforcement ration is needed to make the pile withstand driven force, it needs time after casting to obtain necessary strength and hence there is a gap between casting and driven, and it may suffer from unseen damage due to driven forces. | Suitable for all loading conditions, it can withstand corrosive soils |
| Steel driven pile | It is suitable for all loading condition, it does not suffer damages due to driven forces, it can be extended and cut down. Considerable long driven pile can be used by welding on additional length. | It is subjected to corrosion in marine condition above soil level and subsequently it needs protection, And long piles may go off the line during driving |
Selection of Driven and Cast-in-Place Pile
Table-2 can be used to help in the selection of suitable type of driven and cast in situ pile Table-2: Selection of driven and cast in place pile types based on their advantages, disadvantages, and construction condition| Types of driven and cast in place pile | Suitable condition | Unsuitable condition |
| Withdrawable tube driven and cast in place pile | It is cheaper compare with the other type | It is not good option to use in water bearing sand and squeezing soil |
| Un-withdrawable tube driven and cast in place pile | It is suitable option for squeezing soil, water bearing sand, and when the pile needs driven after ground heave. | It is more expensive compare with the other type of pile |
