Screw piles are increasingly used today for the construction of the fundamental foundations of private houses and in the construction of larger industrial facilities. Supports of this type experience enormous loads and, after the construction of the building is completed, continue to be exposed to the destructive effects of environmental factors. That is why many are now wondering if it makes sense to use screw piles or the service life of these widely available building elements is too short?
A bit of history
Screw-type piles appeared about 200 years ago. All this time they have been widely used in the construction of bridges, moorings, towers, power lines and many other serious objects. There is a lot of evidence that screw piles can last up to 150 years. For example, so far notthe pier that has been standing in sea water on similar supports for more than a century and a half has collapsed.
There are entire museums where visitors can see for themselves the tips of the very first screw piles. However, this does not mean that metal structures will last forever. Negative reviews about the service life of screw piles are fully justified, since the supports made by the handicraft method really collapse quite quickly. The technology of manufacturing building structures is distinguished by a mass of nuances and features. If the production standards have been violated, then the finished piles will not last even a third of the declared period. Therefore, it is very important to pay attention to these subtleties when choosing structures for the foundation.
Service life according to GOST
According to government regulations, screw piles have a service life of 60 to 120 years. Also, the following data is indicated in GOST:
- Electromechanical corrosion of metal in the ground develops at a rate of 0.02 to 0.05 mm per year.
- The wall thickness of the screw and the support itself is at least 5-6 mm.
- Pipe walls decay at a rate of 5mm/0.5=100 years.
In addition, the piles are covered with special two-component type polymer compounds that retain their properties for 7-15 years. This allows you to increase the service life of screw piles under the foundation. If these conditions were violated during the manufacture of supports, then the products will be less reliable and durable.
Is there any difference between cast screw andwelded pile tips
There are no significant differences between such products. Cast tips are made of standard steel marked 35L. The main difference between these support elements is that the helical lines are not welded to the pile cones, but are immediately cast together with them. However, few people know that cast tips are actually welded to the pipe. This means that when using them, it will not be possible to avoid welds.
If we talk about the disadvantages of cast tips, then in their production it is necessary to control the level of quality of casting. In addition, their manufacture is impossible without the use of ultrasonic equipment. The fact is that in the material from which the product is made, small cracks, pores and voids can appear, which will significantly reduce the strength characteristics and service life of screw piles.
Weld tips can be checked by yourself, since even with a visual inspection it becomes possible to assess the quality of the production of products. Piles with cast lines are almost 25% cheaper.
Is there a difference between painted and galvanized pile tips
The main difference is the resistance to corrosion. According to numerous reviews, the service life of screw piles treated with paintwork material is much lower due to the influence of an aggressive environment. The protective coating lasts for a maximum of 15 years, after which metal products begin to rust rather quickly.
Piles that have passed the procedurehot-dip galvanized, do not corrode for 40-50 years. However, it all depends on the aggressiveness of the soil. Thanks to the hot-dip galvanizing method, a 0.2 mm thick layer is formed on the surface of the piles, which does not wear out over a long period of time. In addition, the protective layer of zinc will not be erased during the process of screwing the support.
It is also worth paying attention to the cost of products. Hot-dip galvanized poles cost 25% more than prepainted poles.
What affects durability reduction
The service life of foundations on screw piles can be significantly reduced due to the following factors:
- The impact of moving soils. Under normal conditions, soil has minimal effect on screw piles. However, when it comes to extreme conditions and increased soil mobility, this may affect the performance of the supports.
- Thermal effect. Due to seasonal temperature fluctuations, the metal constantly narrows and expands, its structure is disturbed. The bearing capacity of the supports is significantly reduced, as cracks and pores appear in the material. When using high-quality piles, the number of freezing and thawing cycles of which is enough for up to 120 years, this does not happen.
- Chemical corrosion. If the soil is too acidic, then the rust on the piles will spread much faster.
- Electromechanical corrosion. Similar damage occurs with strong oxidationpiles due to stray currents that may be part of the soil. Most often, poles located near underground cables or various industrial facilities suffer from electromechanical corrosion.
How to increase the service life of screw piles
There are several ways to help extend the "life" of the foundation installed on supports of this type:
- Use piles with thickened walls. Each millimeter of metal increases the service life by approximately 15 years.
- Use supports made of alloy steel only. Piles must be treated with special compounds that prevent chemical corrosion.
- If the products are not protected from rust, you must cover them with anti-corrosion compounds yourself.
- Concrete the inner shaft. Thanks to this procedure, it is possible to protect the structure from moisture ingress and increase the bearing capacity of the support.
It is not recommended to use impact equipment during the installation of piles. This will preserve the structure of products and increase their service life. If the installation of piles was carried out in accordance with the regulations, then the supports will last up to 100 years.
Advantages of screw piles
Despite the problems that may arise during the operation of this type of support, they are still very often used for the construction of foundations and the construction of other structures. This is due to the following advantages of screw piles:
- A medium-sized base can be erected in the shortest possible time (no more than 1-2 days).
- The cost of the foundation is reduced by almost half, making the construction of the entire structure much cheaper.
- Screw piles are ideal for use in unstable ground.
Summing up
Knowing the truth about the service life of screw piles, you can build a durable, reliable and strong foundation in a short time. The main condition is the observance of the technological process for the manufacture of supports and the correct installation of products.
