Pile foundations: Calculating the number of piles and load capacity

If there are difficulties with reliable support on a plot selected pile structure foundation. application alternative technologies in such situations, accompanied by a significant increase in labor and financial expenses. However, in any form requires an accurate preview payment. With the materials of this article, any person will be able to draft their own without errors. About that, what a pile foundation, the calculation of the number of piles and load capacity - read on.

The technology of screw pile foundations

The above is only one example illustrating the possible trouble:

• Problems creating permanent and seasonal high water table. If any, even a reliable piece foundation Housing is not able to ensure the preservation of a stable position.
• Similar problems must be addressed to "the weak" soils.
• With a large depth of freezing can not be ruled heave soil, therefore it is necessary to establish long piles.

Pile-helical foundation is not used during the construction of highway bridges, where excessive load. But it is well suited for wood bath and the house of enough light foam blocksFor metal racks, garage, carport.

Important! Even for a greenhouse or other structure must be relatively easy to do the calculation. It will help to clarify the number and specifications of accessories.

varieties grillages

By static probing, or by using other methods, it is possible to figure out the parameters of soil in a particular plot of land. If they are not sufficient for the anticipated loads, it is necessary to choose the right technology for the formation of the support rods. They will help to stabilize the structure.

From this scheme, the main disadvantages are clear:

• It requires the use of special equipment;
• process is complex and lengthy obtained;
• gelation solution must, however will limit work performance at low temperature.

For a correct comparison with screw products are more suitable for hanging piles in collapsible soils.

When immersed the tip compresses the soil, which helps to create the bottom of the support region. this is not always sufficient to increase the bearing loads. We have to increase the size of the entire column, do the thickening bottom. Use a variety of options for merging with the technology of bored. For example, drill hole wide. It is filled with mortar, which is immersed concrete pillars. But in this case, will have to reckon with the above mentioned challenges, which involve the use of "wet" processes.

These drawbacks are eliminated by choosing a screw pile method. There used products factory production with known technical parameters. This eliminates any errors in creating mortar.

The time limit depends significantly on the temperature of the foundation size, composition. The internal cavity eliminate vibration machines. When frost use special additives. Compound metal framework elements also require certain costs.

Quality products of this type are many. They are difficult to transport, move, driven into the ground. Not difficult to understand that to work need the help of experts, a powerful technique.

If necessary - the technology used in the winter.

Such support can be used in wetlands and other difficult areas. The main thing is that the part with the blades after installation was below the maximum level for the area of ​​freezing. This will help prevent squeezing design buckling forces.

To study was objective, it should be noted not only the advantages but also disadvantages, especially the selection, installation and operation of screw foundations:

• The metal is exposed to the ravages of corrosive processes. Their intensity is increased by a certain composition of the soil. Negative influence stray currents. They form strong electromagnetic fields present near the transmission line, transformer substations, microwave towers and cellular communication.
• Manually screwed piles near the walls is impossible, since at the same time efforts should be attached on both sides. In this case, can not do without specialized equipment.
• Modern products of this class will perform their functions in full for 50 years and more. But these figures are provided not only in the correct position. Useful high-quality corrosion protection of surfaces, the absence of welds. All this adds to the cost.
• The ability of metal piles hold the load is not large compared with reinforced concrete pillars. But for the solution of many problems of domestic construction it is enough.
• The use of this technology makes it difficult, or even makes it impossible to create a ground floor, basements.

Important! Metal rod mounted to a sufficient depth - the typical way of grounding installation. If this connect the corresponding electrical circuit to a screw pile, an error is made. This connection accelerates corrosion.

Plate-pile construction with screw pillars erected rare, due to limitations on loads. Most often uses the following technologies:

• After studying geology and calculations selects the appropriate technical parameters of the product.
• They are screwed to a depth determined by calculation. Applying screw portions simplifies the process. They are additional supports to provide a secure hold in the soft ground. Their presence prevents squeezing pillars heave forces with frost.
• Projecting portion of the ground using an appropriate power cut to the required level.
• For hardening the cavity is filled with a cement-sand mixture. Reinforcement inside not create.
• To the top edge via welding machine attached rectangular area. Embedded metal is also used to connect the various parts of the building, embedded in the concrete when pouring.

type grillage	Picture	Features of the process	typical applications
Metal girder (double-tee)		To strengthen the base tube cavity is filled concrete. Beam welded to the mortgage. Also mono applied screw connection, set top rectangular pad under the support grillage.	This fits well with the foundation prefabricated (sandwich panels). It provides high speed assembly operations, quality connections.
metal channel		compound node is created with the use of technology described in the previous embodiment.	This foundation is able to withstand considerable loads. In addition to frame structures, they set brick and wooden buildings. In any case, you need good protection of metal parts from corrosion.
Wooden timber		The end parts of the beams make the holes. To support site helical piles welded metal pin. This node is going fast. With it, quickly creates a sturdy connection.	This raft foundation is light, so it does not create extra load on the foundation. But we must remember that such a solution is designed for small loads. Its use in the construction of arbors, bathhouses, extensionsand other light buildings.
in situ concrete		The construct is poured like a normal foundation suitable type. Use removable or fixed formwork, reinforcement. Pre-installed in the vehicle mortgage pile cavity.	This solution is used for the construction of heavy structures. Instead, the monolith can be used pile-tape design, install, concrete slabs.

Screw piles and the calculation of the allowable loads

For right choice products should be familiar with the current range of manufacturers. must calculate the loadThat they are able to survive and to compare these data with the actual conditions of future operation. Be sure to take into account the planned service life. After comprehensive analysis of these factors can make accurate conclusions.

Screw piles: sizes

To buy component parts for a specific project without errors, it requires a precise calculation. But first you need to study the range of modern shops. This information will help to clarify the personal requirements.

The following table summarizes the characteristics of the production line "SAF". These products are created with the use of welded joints.

Note! The table shows the value of the standard sizes. With increasing length, each additional 10 cm evaluated from 25 to 30 rubles., Depending on the diameter.

You should also pay attention to the nuances of the following:

• Quality production is distinguished by strict organization, using standards (SNIP, TU). Conformity of the product is confirmed by official certificates.
• Control: deviation from the vertical piles, defects welds, pipes form blanks.
• Manufacturers indicate the allowable effort that should not be exceeded in the process of screwing.
• To reinforce the structure of the blades and the thickness of the tip make more as compared with the tube walls.
• Increased corrosion resistance with phosphating, applying the paint (film thickness of 150 microns or more). Some manufacturers recommend the use of tape from a polymeric material which is wound pipe at the transition from ground to air (width 20-30 cm).

Separately it is necessary to examine that part of the pile design. That she is experiencing the greatest load in the process of screwing, when passing through the dense layers of the soil. She is subjected to considerable mechanical stress during operation. Headroom can be repaired should the need arise. If it gets off the blade - the repair is difficult, and the corresponding section of the foundation may collapse.

Molded lugs higher than the examples above about 25% -35%. But their application allows you to create a more robust design. The absence of welds provides greater resistance to corrosion processes. Such a foundation is able to carry out their functions 80 years or more. Therefore it is possible to obtain good economic results. But in any case, high-quality technology assembly operations should be applied to take into account the chemical composition of the soil, the presence of stray currents.

When you select should give preference to products responsible producer. These relatively simple products are produced not only reputable companies, but also numerous workshops. Application handicraft methods can not provide a perfect quality of metal, to create reliable connections. There are cases when welding lugs after special grinding surface and coloring issued for more expensive alloy modification.

Help prevent problems scrutiny. The store should be to find out the origin of the product, see the accompanying documentation confirming certificates.

The following solutions are used to address specific engineering tasks:

1. This option is designed for the construction of buildings in the Far North, or when working in extreme cold. Notched tip, lighter than the standard, it is immersed in the frozen ground. The width of the blades is reduced to the values ​​shown in the figure. a wall thickness increase of up to 16 mm.
2. This design is suitable for the installation of pier foundation in flooded soils.
3. So that when the big frost heaving forces pushed the pile, the diameter of the blades is increased to 800-850 mm.

Related article:

The foundation on screw piles with their hands. This technology is used to accelerate the construction is not too heavy buildings and other architectural structures. In this article you will find a step by step construction of structures and useful advice from professionals.

Permissible loads on the screw piles

Design of the foundation starts with the calculation of bearing capacity of the pile. This result will help to find out what the structure will be set to the appropriate support. It should not be forgotten that is essential not only structural strength, but also a certain geological characteristics of the ground land.

For calculations use simple formula NA = RNS / KWhere:

• NA - the unknown quantity, load-bearing capacity of one product;
• RNS - the estimated carrying capacity of the reference pile, which is calculated based on the "ideal" size, the strength of the soil;
• TO - correction factor which takes into account possible changes in relevant parameters.

The calculated value is not difficult to figure out the formula PHC = P * SGWhere:

• P - is the area of ​​the helical part of the pile (take appropriate dimensions node vertical projection together with the central part);
• SG - the value of soil resistance on the land (the table with some values ​​listed below).

Note! During the research it is necessary to consider that are important characteristics of the ground, which is located on the same level as the blades installed pile.

For the calculations should take into account soil characteristics limit state, so you need high precision survey work. If you order a comprehensive analysis of the specialized company, the required data will be received.

Samples of lot is checked using professional techniques. This option is more expensive, but the data could be used with a minimum correction coefficient K (1.1 to 1.2) in the formula for calculating the bearing capacity.

Less accurate values ​​obtained during test drilling with the instrumental measurement of force, which has to be applied to the end walls. There will also need to attract relevant specialists. This method is cheaper and faster than the previous version. The correction factor can be set from 1.2 to 1.25.

Despite increased the complexity of the process, it is difficult without professional skills to ensure the accuracy of the results. When selecting this technology experts recommend to use when calculating the correction factor of at least 1.4.

Note! A horizontal load calculations do not apply above.

Calculator for screw pile bearing capacity

The SCAD 21, on a dedicated construction forum Forumhouse, in Lira - will not be difficult to find the corresponding blocks. Some tools can be used online.

The Scud or in our simplified program in standard algorithms need to perform the following steps:

• Indicate the size of the product.
• Note what kind of soil prevails on the estimated depth of the installation of the blades of the support structure.
• In a separate column make a mark on the method that was used to test the load capacity of the soil. This is required for automatic determination of the correction factor.

In the example given is not the cost of calculation. It is made after the updates, which are discussed below.

Calculation of pile foundation

To find out exactly how much you need to screw piles for the foundation, it is possible only after the summation of the future loads. Below is a detailed guide. But you should know that it is necessary to take into account not only the basic building construction, but also finishing materials. Possess significant weight door and window units, engineering Communication. It is necessary to add the weight of furniture, major appliances, boiler and other equipment.

Note! The next section shows the manual. It can help you learn how to calculate the correct number of piles for the foundation. You need to add the weight of the permanent residents and guests. Handy small supply of loads, even when careful consideration of the smallest details. He will prevent the occurrence of dangerous and emergency situations in the course of operation.

A calculator for calculating the total load exerted on the screw-pile foundation

The following are notes to the calculation program:

• Area partitions and external walls can be counted in person. For this purpose, the existing drawings. More accurate data are obtained by subtracting the area of ​​door and window units. If this is not done, the strength of the foundation will be created with a margin. At this stage in the corresponding column is selected calculator base material constructions.
• Information about the area floors will be useful to calculate the mass of overlapping. It also indicates the material based on reinforcement and other important details of the opening in the corresponding list item. It is necessary to subtract the empty areas for mounting staircases.
• Next selected type roofing. If there is no specific option, note the materials that are close by weight. For example, a roofing material coating is approximately equal by weight of a soft bituminous roof with the same number of layers. Weight roof system is added automatically by the program based on the selection.
• In the cold season a considerable weight can create snow load. For accuracy it is necessary to note the angle of slope relative to the horizontal.

• (In kg per sq. M. Load) are entered into the calculator is not necessary flight data in Fig. It is enough to specify the area in which the property is built.
• Weight grillage of wood insignificant, so it is considered when calculating the increasing dimensions of the corresponding walls. If Strapping pile foundation used a metal channel, other heavy materials, a separate calculation.

After checking the data, press a virtual key confirmation. The calculation is performed quickly, without additional intervention from the user. To determine whether enough strength supports, the obtained value is divided by the load-bearing capacity of the unit part (HC) that is calculated in advance.

Suppose that for frame house Get the number of piles equal to 17. This is not the final result. With reference to the drawing of the building with walls and contour operate distribution of control points. They are placed at the interface of protecting designs in the corners. On the straight sections of building structures installed piles in increments of no more than 300 cm.

The above calculation is used for the design of permanent structures. Small outbuildings, fences and other light structures can be built on less solid ground. But we must remember that some support will be needed for heavy process equipment. A similar additional strengthening is set under the column, retaining a large weight, other important components of the power frame.

If difficult terrain and on steep slopes height difference may be too large. In some cases, the need piles of different lengths. They are screwed so that the remaining stocks of the estimated height of 30 cm to 60 cm. Excess marked with leveling, cut to the same level. Further fixed end walls, grillage adjusted according to a selected embodiment.