The service life of screw piles under the foundation

Screw piles are now increasingly used forthe construction of the foundations of private houses and the construction of larger industrial facilities. Supports of this type are experiencing huge loads and after the completion of construction, buildings continue to be subjected to the ravages of environmental factors. That is why many are now wondering if it makes sense to use screw piles or is the service life of these widely available building elements too short?

A bit of history

Screw-type piles appeared about 200 years ago.All this time they were widely used in the construction of bridges, wharves, towers, power lines and many other serious objects. There is considerable evidence that the service life of screw piles can be up to 150 years. For example, the wharf, which has been in seawater on similar supports for more than a century and a half, has not yet collapsed.

There are entire museums where visitors can personallyConsider the tips of the very first screw piles. However, this does not mean that metal structures will last forever. Negative reviews about the life span of screw piles are quite justified, since the supports made by the artisanal method really quickly collapse. Manufacturing technology of building structures is characterized by a mass of nuances and features. If production standards were violated, then ready-made piles will not last even a third of the stated period. Therefore, it is very important to pay attention to these subtleties when choosing structures for the foundation.

Service life in accordance with GOST

According to state regulations, the service life of screw piles is from 60 to 120 years. The following data is also indicated in GOST:

• Electromechanical corrosion of metal in the soil develops at a rate of from 0.02 to 0.05 mm per year.
• The thickness of the screw walls and the support itself is not less than 5-6 mm.
• The walls of the pipes fade at a speed of 5 mm / 0.5 = 100 years.

In addition, the piles are covered with specialpolymeric compounds of the two-component type, which retain their properties for 7-15 years. This allows you to increase the life of screw piles under the foundation. If these conditions were violated during the manufacture of the supports, the products will be less reliable and durable.

Is there a difference between cast screw and welded pile tips?

There are no significant differences between such products.Cast tips are made of standard steel labeled 35L. The main difference between these elements of the supports is that the helixes are not welded to the pile cones, but are immediately cast with them. However, few people know that in fact cast tips are welded to the pipe. This means that when using them it will not be possible to avoid welds.

Если говорить о недостатках литых наконечников, then during their production it is necessary to control the quality level of the shower. In addition, their production 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 the service life of screw piles.

Welded tips can be checked independently, because even with a visual inspection it becomes possible to assess the quality of the production of products. Cast line piles cost almost 25% less.

Is there a difference between painted and galvanized pile tips?

The main difference is the resistance tocorrosion. According to numerous reviews, the service life of screw piles treated with paintwork material is much lower due to the influence of aggressive environment. The protective coating lasts a maximum of 15 years, after which metal products begin to quickly become covered with rust.

Сваи, прошедшие процедуру горячего цинкования, не exposed to corrosion for 40-50 years. However, it all depends on the aggressiveness of the soil. Thanks to the hot-dip galvanizing method, a layer with a thickness of 0.2 mm is formed on the surface of the pile, which does not abrade over a long period of time. In addition, a protective layer of zinc will not be erased in the process of screwing the support.

Also pay attention to the cost of products. Hot dip galvanized supports will be 25% more expensive than products treated with paintwork material.

What affects the reduction of durability

The life of the foundation on screw piles can be significantly reduced due to the following factors:

• Impact of mobile soil.Under normal conditions, the soil has a minimal effect on screw piles. However, if we are talking about extreme conditions and increased mobility of the soil, then this may affect the performance characteristics of the supports.
• Thermal exposure.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 defrosting cycles is enough for up to 120 years, this does not happen.
• Chemical corrosion. If the level of acidity is exceeded in the soil, the rust on the piles will spread much faster.
• Electromechanical corrosion.Such damage occurs during strong oxidation of piles due to stray currents, which may be part of the soil. Most often, supports that are located near underground cables or various industrial facilities suffer from electromechanical corrosion.

How to increase the life of screw piles

There are several ways to help extend the “life” of a foundation installed on supports of this type:

1. Use piles with thickened walls. Every millimeter of metal increases the service life by approximately 15 years.
2. Use supports made of alloy steel only. Piles should be treated with special compounds that prevent chemical corrosion.
3. If the products are not protected from rust, it is necessary to self-coat them with anti-corrosion compounds.
4. Concreting the inner barrel. Thanks to this procedure, it is possible to protect the structure from moisture and increase the bearing capacity of the support.

В процессе монтажа свай не рекомендуется use impact equipment. 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.

The benefits of screw piles

Despite the problems that may arisewhen operating supports of this type, 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:

• The base of medium size can be built in the shortest possible time (no more than 1-2 days).
• The cost of the foundation is almost halved, making the construction of the entire structure much cheaper.
• Screw piles are best suited for use on unstable soils.

Summing up

Knowing the truth about the life of screw piles, you canto build a durable, reliable and durable foundation in a short period of time. The main condition is compliance with the technological process of manufacturing supports and the correct installation of products.