Structural and geometric parameters (standard sizes) of screw piles 57, 76, 89, 108, 133, 159, 219, 325

Pile foundation
Low bearing capacity or water saturation of the soil is one of the most important problems arising during the construction of any building. Weak soils cannot support the mass of the building, as a result of which it inevitably begins to sag. If subsidence occurs unevenly, this inevitably leads to deformation and subsequent destruction of the building. The same thing can happen when the foundation is squeezed out by the forces of seasonal heaving. A pile foundation designed for the construction of buildings on subsidence soils allows you to avoid such troubles.

What is a screw pile screw pile

Screw piles are firmly fixed in the ground
Screw piles are firmly fixed in the ground Screw foundations came into civil engineering quite recently, somewhere in the middle of the last century. Initially, foundations of this type were used in military construction, as quickly installed foundations for various military structures.

Over time, the advantages of quickly installed foundations were also appreciated in civil engineering.

They are made in a factory. The structure is a metal pipe of different diameters placed in the ground. At the lower end of the rod there are blades and a point. Some types are made with an open lower end.

Calculation of screw piles for the foundation

The installation of screw piles is preceded by calculation of the required number, screwing depth and determination of the distance.

In particular, the calculation of screw piles is carried out according to SNiP 2.02.03-85.

The number of piles in the foundation and their dimensions should be determined based on the condition of maximum use of the strength of the pile material and foundation soils at the design load allowed on the pile. Therefore, in order to determine how many screw piles are needed for a house (6x6, 8x8), you should have complete information about the specified parameters. They also determine the optimal distance between screw piles during installation.

Screw support installation technology

Installation of screw piles

Installation of screw piles The technology of its installation depends on how many meters the longitudinal size of the support is.

Screw piles 2 - 3 meters long with a small diameter are screwed into the ground manually by the efforts of 2 workers. A small diameter pipe is threaded into the technological holes in the upper part of the trunk, which serves as a lever for screwing the rods into the ground.

With a large metal rod, special mechanized installations with a rotating element are used to immerse it in the ground.

Supports of this type are used in almost all types of soil except rocky foundations.

Characteristics of screw piles - types, types, sizes

Due to the fact that screw piles are manufactured according to specifications and are in demand for buildings for various purposes, on different types of soil, several varieties are presented on the market, and a generalized classification is given in the table:

Technical characteristics of each variety

According to soil characteristics:

• seasonal freezing soil (SFS). In this case, ordinary piles are used, which are screwed into the soil without preliminary drilling. Visually, such piles are distinguished by the classic type of blade and hermetically welded pile cone. The installation site of the pile is filled with cement-sand mortar;

• permafrost soil (PFSM). Screwing into the soil requires preliminary drilling of the soil. Visually, they are distinguished by fine rifling along the entire length of the barrel. The installation site of the pile is filled with sand.

By type of pile tip:

The purpose of the tip is to make the process of screwing the pile as easy as possible.

• cast tips for screw piles. They have a significant cost and are justified in the presence of very dense and/or permafrost soils. The cast tip is capable of screwing the pile into the most difficult soil without destruction without deformation;

• welded tips for screw piles. A cheaper option, however, has a weak point in the form of a weld. This type of pile is in demand by developers who screw the pile by hand. Because there is a risk of deforming the pile when twisting by machine. In this case, the pile is twisted to the stop (obstacle), and not to the calculated depth.

By number of blades:

• single-blade. Piles with one blade can only be used in dense soils, in the case where the tip of the pile will rest against a solid base;

• multi-lobed. The number of blades can be from one to six. The weaker the soil, the more blades the pile should have, this is due to the fact that multi-bladed piles are more resistant to pushing/pushing and horizontal loads.

Types of screw piles (single-blade, bi-blade and multi-blade)

By blade size:

• broad-bladed. Blades are considered wide if their diameter exceeds the diameter of the pipe by one and a half times or more. According to individual specifications, it can be in the range from 200 to 350 mm. The significant diameter of screw piles allows them to maintain a stable position in soft soils. Deviation within +/- 9 mm;

• narrow-bladed. Designed for frozen and dense soils. Due to the fact that the diameter of the screw pile blade is insignificant, it is easier to screw it into the ground.

The metal thickness for the blades varies from 9.5 to 12.5 mm.

By pipe size:

Pipe dimensions are a collective parameter, it includes:

• pipe (barrel) diameter – 159-325 mm. Among the most popular are 89, 108 and 133 mm;
• pipe length – 3-12 m.p. Deviation within +/- 50 mm;
• metal thickness – 8-12 mm. Deviation within +/- 2 mm.

Thickening the walls, in turn, increases the cost of the screw pile, but reducing the thickness reduces its performance characteristics. The international standard ICC AC358 regulates the wall thickness of the pile shaft to be 8 mm. for use in neutral soil, and 9.5 mm for chemically active soil.

Note. There are piles on the market with a wall thickness of 3-4 mm.

The use of standard sizes of screw piles depending on the purpose of the structure is presented in the table:

How to calculate the length of a pile calculate the length of a pile

For calculations, it is important to know the thickness of the dense soil layer and the freezing depth

For calculations, it is important to know the thickness of the dense soil layer and the freezing depth. The dimensions of screw piles directly affect their cost. The cost of purchasing and installing them depends on deciding how many meters the pile will be long.

When determining their length, they are guided by the following factors:

• depth of dense soil layer;
• soil freezing depth; blade immersion depth;
• distance from the top of the support to the mounting holes;
• height of the base. Let's consider each factor separately.

Depth of dense soil layer thickness of dense layer

To build a foundation, you need to know how many meters deep the rod should be immersed in order to reach the load-bearing layer of the earth.

In the regional department of architecture or a similar institution, you can get a copy of the vertical survey of the soil occurrence at the construction site. A vertical photograph will show how many meters deep dense layers of soil lie.

If this is not possible, use a hand drill to obtain soil samples.

Soil freezing depth soil freezing

For the foundation, it is important how deep the soil freezes. The amount of soil freezing determines how many meters the thickness of the soil is subject to heaving.

It should be kept in mind that not all soil types are susceptible to frost heaving.

The length of the rods should allow its lower end to be below the soil freezing level.

If the screwed-in rod is located in the zone of the freezing layer of earth, then it will be pushed upward by the frozen earth increased in volume. This can cause serious damage to the foundation of the structure.

Pile blade immersion depth

The blades must reach a dense layer of soil. The position of the upper edge of the blade depends on how many meters the pile is immersed in the load-bearing layer of soil. The upper edge of the blade should be in a dense layer of soil. Considering the distance from the blade to the lower end of the rod, the length of the pile from the ground surface to the tip of the tip can be determined. To learn how to install screw piles wisely, watch this video:

Diameter

For 10 years, the screw base has been in such wide demand. The reason for this demand is associated with a large number of advantages, which include the following: strength, durability and reliability. Today, piles are produced in a wide variety of sizes, with different diameters and for a variety of purposes. Let's look at the most basic dimensions of screw piles.

You can learn about the load-bearing capacity of screw piles 108 from this article.

Diameter 57 mm

This option has a load-bearing capacity of 800 kg. For such a product the presented load is not dangerous, even if the installation process is carried out on heaving soil. It is allowed to use such a foundation on waterlogged soil and on soil with an uneven surface.

This type of support is used when installing fencing structures and constructing buildings that are not too heavy for utility purposes. This includes gazebos and garages. The process of installing screw piles with a diameter of 57 mm can be carried out independently by hand. Due to its small size, installation work does not take much time.

What are the disadvantages of screw piles can be found in this article.

The advantages of this type include a long service life. They can serve you for 90 years. This advantage is achieved due to invulnerability to the negative effects of climate, reliability and durability.

You can read about the structure of a grillage on bored piles in this article.

Diameter 89 mm

For such a product, the load-bearing capacity can be 1.4 tons. The scope of use of screw piles of this type is the construction of houses and buildings in wetlands and peat areas. This is achieved thanks to its excellent ability to withstand high loads.

This option is allowed to be used in the construction of garages and fencing structures. People also actively began to use screw supports with a diameter of 89 mm in the construction of summer houses and baths.

You can find out how long it takes for a concrete foundation to dry from this article.

They can also be used in the construction of piers and river berths. The installation process is carried out using special equipment. Of course, you can carry out such events manually, only if you have the necessary skills.

What thickness of the foundation should be for a two-story house can be found in this article.

Diameter 108 mm

For such products, the load-bearing capacity reaches 3.5 tons. I use them in the construction of frame-panel houses or in the construction of log buildings and houses made of timber. This type of piles can also be used during the installation of hangars and heavy fences. The installation process is carried out only mechanically and using special equipment.

You can learn about what grade of concrete is needed for a strip foundation from this article.

Diameter 133 mm

These products have a load-bearing capacity of up to 6 tons. They are used on any terrain during the construction of large buildings using aerated concrete blocks or bricks, and in the construction of monolithic structures.

The installation process requires the use of special knowledge and skills, and also cannot do without special equipment. The advantages of this product include:

• efficiency;
• excellent reliability;
• long service life;
• all-season and special strength, thanks to which installation work can take place in any climatic conditions.

You can read about what brand of concrete is needed for the foundation of a house in the article.

Distance from the top of the support to the mounting holes of the pile house

Mounting holes should be located 100 mm from the top of the structure

The mounting holes should be located at a distance of 100 mm from the top of the structure. The mounting holes in the top of the pile structure are needed to pass the lever through them to rotate and screw in the support. A small diameter metal pipe is used as a lever.

How far the mounting lugs should be above ground level depends on the height of the building’s base. Typically, mounting holes are made in the pipe at a distance of 100 mm from the top of the structure.

When constructing a foundation of this type, it should be taken into account that the upper sections of pipes with mounting lugs are cut off. Then, mounting parts are welded to the tops of the pipes to secure the grillage structures.

Determining the height of the ground part of the trunk affects the formation of the total length of the foundation support.

Why don't developers trust pile foundations?

Despite the widespread use of pile foundations, some developers are cautious about their durability. The fact is that when calculating the number of support elements, as well as their parameters, the principles and formulas set out in SP 24.13330.2011 are used.

The calculation methodology described in the documentation is based on simplified models of interaction between soil and foundation. Thus, the design does not take into account the presence of stray currents, as well as the aggressiveness of the soil and groundwater. Negative factors include the heterogeneity of the soil composition on the site. The listed aspects together reduce the operational life of the foundation for decades.

Experts advise choosing a supplier of screw piles from companies with a proven reputation, since some unscrupulous manufacturers use low-quality steel and skimp on the thickness of the anti-corrosion coating.

Example of calculating the length of a screw pile

Summarize all the data obtained from the soil study. The construction site is located in the region of the Central Russian Upland, where the depth of soil freezing and the depth of dense soil are the same and amount to 1.8 m. Taking into account the height of the base (0.5 m), the distance of the installation holes from the top of the pile (0.1 m), the depth of penetration of the screw into the dense layer of soil (0.5 m) and compensation for calculation inaccuracies (0.1 m), the length of the pipe will be equal to:

1.8+0.5+0.1+0.5+0.1 = 3.0 m

The length of the pipe with the prepared head will be shorter due to the removal of part of the pile with mounting holes. This must be taken into account when making the support.

How to extend operation?

To extend the service life of a pile foundation, owners should pay special attention to the quality of structural elements, as well as carry out a number of additional measures during installation work:

1. 
   Selecting piles from high strength steel . If a geological analysis of the soil shows that the site has very aggressive soil, then it makes sense to choose pipes with a wall thickness of at least 5 mm. An increase in the indicator by even 1 mm will increase the service life of the foundation by several decades.

2. Power elements made of alloy steel . This material compares favorably with its performance characteristics compared to conventional metal. The high cost of such piles is offset by the increased period of operation of the foundation.
3. Coating with an additional layer of anti-corrosion protection. Despite the declared quality and wear resistance of supports treated with hot-dip galvanizing, this protection option does not work well in the event of destruction occurring directly in the ground. To protect the foundation from electromechanical and chemical corrosion, experts advise covering the metal with an elastic layer of material based on epoxy resins, polyurethane, etc.
4. Concreting screw piles. This is the simplest and most effective method of increasing the service life of supports. Concrete poured into the internal cavity of the pipe displaces all oxygen, eliminating the risk of oxidation and, as a result, destruction of the pile from the inside.

What to look for when purchasing

Considering the advantages of a pile-screw foundation and a reduction in the construction budget, when purchasing you need to take into account the following nuances:

• Pile body: The pipe must be seamless, new, preferably made of 30ХМА steel
• Blades: Cast, as they reduce the number of welds, the areas around which become less strong. It is necessary to choose products with two blades that increase both load-bearing capacity and stabilization in the vertical plane.

A cast tip with a blade is preferable to a welded one.

• Tip: Cast together with the blades, although there are modifications on the market with a cross-shaped peak made of three triangles of sheet steel, welded and options made from a pipe body.

For example, SHS is sold with a body cut at 45 degrees, the blades of which begin without reducing the diameter. This leads to a decrease in the bearing capacity of the foundation and increases the torque.