Steel piles are precast piles or are pieces that are cast in order to be driven. In the case of precast or fully made piles, there are two classifications, which are small displacement hollow piles and solid piles. Small displacement hollow piles refer to steel tubes and are used when such a steel pile foundation is recommended. When solid piles are required, the precast steel piles are used in their entirety.
Classification of steel piles
In the case of driven piles, mainly steel tubes and precast concrete piles can be classified. In the case of steel piles, closed end tubes and open ended tubes are used. Generally, steel piles are classified as follows.
- Screw piles
- On disc piles
- Piles in H
- On tubular steel piles
Most used steel piles
The steel piles that are most used are rolled steel H-piles and pipe piles, pipe piles are characterized by having open or in other cases closed externalities and in this way are introduced into the ground. (I) or wide flange section piles can also be used as a pile foundation.
The sections that are manufactured in the shape of (H) are used and preferred more than those that have the shape of (l), this is because the section in (H) has the same thickness in the flange and the band. In the case of the (l) -shaped section, its thickness on the band is less compared to the thickness of its flange.
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If Q is the structural capacity that is allowed, then A is the cross-sectional area of the steel and the stress that the steel has is given by f s , then
If Q is the allowable structural capacity, A is the cross-sectional area of the steel and the stress in the steel is given by f s , then
Q all = A xf s
It should be noted at the time of geotechnical investigation that the design force is determined as design Q and this must be within Q all .
How are the steel piles connected?
Next, we will present in figure number 1 how an (H) shaped pile is spliced using the rivets and welding, as the requirement stipulates, the steel piles can be riveted or welded at the time they need to be spliced.
Figure number 1: in this you can see the joint of a pile at (H) using (1) Welding (2) bolts and rivets.
The piles at their ends, as mentioned above, can have a conical or flat bottom as can be seen in the following figure 2. In this the connections are welded.
Figure number 2: in this you can see the steel piles with conical and flat bottom.
The piles have driving points or slippers in order to facilitate their movement on soils that are characterized by being hard like dense gravel. Shale and soft rocks. The previous figure shows two types of footings that can be incorporated into the piles.
Types of steel piles
There are different types of steel piles among these are tubular steel piles, screw piles, disc piles, H-shaped piles. Next, we will explain each one of them.
Tubular steel piles
Pipe piles are used as friction or support piles. These piles are tubes that do not have a seam and are made of steel that is formed by welding. The conduction of this type of pile can be done with the help of its bottom, either closed or open. For this reason, there are:
- The closed piles;
- And the open end piles.
Closed end tubular piles
This type of tubular pile, similar to a conical element, can be made of steel or cast iron, its open bottom is joined using welding. This is known as the tapered shoe. Once the pile is driven into the ground, the pipe is filled using the required amount of concrete.
Open end tubular piles
Open-ended tubular piles are often used to penetrate hard or rocky strata. These piles are driven into the ground and the soil material that remains inside the pipe is extracted using compressed air or by injection of water. After it is free of the material inside and is in the depth that is needed, it is filled with concrete.
Diameter of tubular piles
The tubular piles have diameters ranging from 0.25m to 1.2m. its thickness also varies from 8 to 12 mm. For pile bases that are longer than 30 inches, this type of pile has optimal performance.
Screw or helical piles
This type of pile is made of cast iron or steel. They are characterized by being a long shaft that at its end has a screw base or has a helix shape. The axis with which this type of pile has can be solid or hollow.
The helical piles have a base that in turn has a diameter that ranges between 0.45 and 1.5 m. The end of the pile is driven into the ground using a specialized electric motor that assists in the penetration process.
In which cases are screw piles used?
Screw piles are widely used in soils that are characterized by being loose or clayey. These piles are responsible for increasing the support area that the soil has.
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This pile has an arrangement very similar to that of helical piles, this is due to the fact that they have a cast iron disc attached to their bottom. These piles are often used in sandy or soft soil types, they are very suitable because they allow the sinking of the disc piles during the water injection process.
Disc piles are used very frequently in marine construction projects, since these areas require a higher penetration compared to other types of projects.
Piles in H
Rolled steel H-beams made like bearing stacks are one of the latest and most innovative technologies developed by the foundation industry. The hard driving of the pile in the soil strata results in a large amount of stresses and impact forces. H-shaped piles are characterized by high stress support. These are frequently used in order to penetrate areas that have rock or any other type of hard layer.
For its installation, no other additional process such as injection or extraction is needed than if it is used for the installation of other types of steel piles. Thanks to the fact that the H-piles have a small cross section, it is easier to move them on the ground.
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Advantages of H piles
H piles have several advantages that you can take advantage of in your projects, we are going to tell you about these below.
- The H-shaped piles need less space to move them
- They are easy to handle
- Its penetration can be made closer to an existing structure
- The unusual amount of displacement that is caused in the near area during H pile penetration is very small
- It is very easy to carry out the process of splicing the piles in H
- The maximum depth to which they can be driven is 100 m
- They perform compaction and friction functions
- Its main application is in trestles, cofferdams, bridges and retaining walls
Corrosion of steel piles
Steel tubes, regardless of the type of material used to make them, have a great chance of corrosion. To avoid this situation, the piles are coated with coal tar or a specialized coating to protect them from corrosion. Sometimes chemicals or materials are encased in concrete to prevent corrosion.