In the civil engineering works piles are used as supporting structure or foundation and as a contrast in slope reinforcement works.
The foundation pile is a type of deep foundation, also known as indirect foundation that differs from the direct one for its capacity of transmitting a part of the vertical load, along the lateral surface, by friction.
This type of foundation has the advantage of reducing the long-term subsidences, in order to take advantage of resistance (either for support or friction) of deep and load-bearing soil layers (surpassing in depth soft and unsuitable grounds and cavities).
Area of application
Foundation piles are requested when it is not possible to use ordinary shallow foundations; the use of peak piles allows to reach a substrate of suitable carrier capacity.
Foundation piles are used when:
- Defect of bearing capacity of the surfacing ground;
- it is technologically impossible to perform surface foundations (offshore structures, mixed ground subjected to high filtration gradients, etc)
- in case of incompatibility of absolute or differential subsidences with type of structure to be founded
- it is necessary to isolate the foundations of the surface soil, when it is subjected to erosion or other physical phenomena that periodically or occasionally change the physical features.
We can find the following types of foundation piles, depending on implementation process:
BORED PILES
The category includes all the in-situ posts in plain or reinforced concrete; through these posts, the tube (with no shoe) descends into the ground by means of special augers or percussion probes.
The bucket falls from above by its own weight, hits hard on the ground and penetrates thanks to the cutting edge on the end.
After removing the waste material deposited in the body of the probe, the casing tube is inserted into the ground.
The pile can be reinforced with a metal cage, composed of longitudinal rods connected with a spiral able to support the static load.
The cage is inserted into the tube before the jet.
Pile-driving inserted by percussion (recoverable formwork).
Plain or reinforced concrete piles belong to this category. They are obtained by pouring and strongly compacting fresh concrete in a metal formwork driven into the ground. The removal of material is not necessary because the formwork is closed at the end by a metal pile shoe (recoverable or lose) or by concrete plug.
The formwork is gradually extracted and recovered.