Pile Foundation Details: 4 Types Details May You Don’t Know
Pile foundations are often used in building a bridge to successfully transfer the load to safe strata below.
These piles could be either cast in place or precast. These pile foundations are most of the time made up of steel piles, concrete piles, timber piles, and composite steel-concrete piles.
In this article, we will discuss various details of pile foundations like a screw and helical piles. We would also be discussing the section details of the pile foundation and relevant construction details.
Pile Foundation Details
Screw piles are one of the steels-made ground anchoring systems typically used for making steel foundations. Usually, there is a use of high-strength steel or alloys in their making.
They could have a hollow or compact cross-section of varying sizes. They are often welded to the pile shaft as per intended ground details.
Their design is usually dependent on several factors, not to mention:
- Geotechnical parameters of soil like shear strength, pore pressure.
- Environmental constraints like corrosion. It is not suitable to use these types of piles in areas that are more exposed to high pore pressures, which will in turn result in increased corrosion.
- The design of the life of the structure is also an important parameter. For a structure with longer lives, these piles would be more exposed to corrosion and hence they are not the preferred alternative.
- Lastly, the design of the screw pile would depend on the loading needs.
Their design is also governed by the local design guidelines and building standards in the area of their construction.
Helical Pile foundation systems on the other hand consist of strong galvanized steel sections with a helical lead section screwed.
The helical lead section is screwed deep into the ground until they reach stable soil. These are then attached at the top to the existing foundation.
These types of piles are not only used on new structure construction sites but can also be frequently employed to repair existing failing foundations.
One of their major use is in the areas of tight access or the situations in which the structure is undergoing renovations and additions. These types of piles are also used in improving the load-bearing capacity of the structure, make it more structurally integral, and upgrade its load-carrying capacity.
The factors, which govern the design of helical piles are more or less similar to screwed piles.
Pile Foundation Section Details
- For timber piles, the cross-section could be square or circular shaped. It is a solid cross-section usually. The dimension of the cross-section is dependent on the amount of compressive load, piles have to take.
- For Concrete piles, there is a use of reinforced concrete cross-section with steel rebars.
Usually, the cross-section is a box or circular shape.
There are two types of reinforcement in it. One is longitudinal reinforcement, which responsible to take compression and flexure loads. The other type of reinforcement is shear reinforcement, which is responsible for the encasement of the pile and shear loads.
- The dimension of the cross-section is dependent on the amount of compressive load, piles have to take.
- For steel-concrete composite piles, the cross-section is again in the shape of a square or a circle.
The concrete is infilled in the hollow steel cross-section. Sometimes the infilled concrete is also reinforced to cater to additional loading demands.
The dimension of the cross-section is dependent on the amount of compressive load, piles have to take.
- Lastly, for steel piles, there is a variety of the shape of cross-sections depending on the type of pile. They could be solid or hollow steel circular, square, or rectangular cross-sections.
There are some especially scaped cross-sections in case of screw piles or helical piles.
Pile Foundation Construction Details
In this article, we will be discussing the construction details of precast-driven piles. Their construction differs from the cast-in-place pile.
Following steps are generally followed for the pile foundation construction.
- At first, they are cast at ground level in case of concrete piles. In other cases, they come prefabricated from the factory.
- Then they are driven into the ground using a pile driver. Pile drives is a machine that can hold the pile perfectly vertical.
- Afterward, the pile is hammered into the ground step by step using the blows. Each blow is generated by hitting the pile cap with heavyweight, lifting the weight, and then hitting it off again.
During the hammering process, there is the covering of the cap on the top of the piles to avoid its disintegration.
In the case of screw piles or helical piles, the piles are driven into the ground using a pile driver. The pile drives constantly rotates the piles, while also keeping them in the vertical positions.
- The piles are hammered into the ground until the ground starts to resist their insertion or hard strata is achieved, upon which a load of structure can be safely transferred.
Reinforcement in Concrete Piles
Unlike other types of piles, in the case of concrete piles, a difficult step is to design the reinforcement. These reinforcements can take a variety of shapes and sizes.
Two factors affect the size and location of the reinforcement: the amount of axial load and the required level on the encasement.
There is a variety of software available in the market for the design of reinforcement. This software allows you to design the piles as per different building codes around the world. Rocscience provides the majority of geotechnical design software.
To conclude, screws and helical piles have identical design steps, but they both have different types of cross-sections. Both of them are the screwed piles with similar construction technology.
The cross-section of steel, concrete, composite, and timber piles was also discussed. The dimension of the cross-section is dependent on the amount of compressive load, piles have to take.
Different construction steps of precast piles like a screw and helical piles are also discussed.