To organize a pile foundation, it is necessary to perform work on pressing reinforced concrete supports into the ground. After that, a monolithic slab or tape is erected, which will distribute the load. Such a structure is called a grillage. But first, builders build a pile field on which beams or slabs are installed. It is the quality of the calculation and markup that determines the technical parameters of the object under construction.
General information
Pile field - a special structure that is being built so that the concrete foundation of the building is strong. If a foundation of a screw, reinforced concrete or bored type is organized, then in any case, such an installation will initially have to be built. The structure is used as a foundation for the construction of residential or industrial buildings after the grillage has been erected.
If there is a problem soil at the construction site, then most often steel supports are built under the house - elements that distribute the load of the structure on the soil layer where the underground part of the structure will be located. To comply with product specificationsstructures should be driven to a depth of 3 to 15 meters, since only in this case they will be in a stable and deep layer.
You should know: the construction of the walls begins after the construction of the grillage, the bearing surface for which is the pile mesh.
Location of supports in the foundation
The load of the supporting structures of the structure and the shape of the grillage are factors that determine how metal, reinforced concrete or wooden rods will be placed in the foundation pile field. There are such ways of arranging supports:
- Pile bush - a method in which piles are combined into one compact structure. In this case, the grillage is performed in such a way that the ratio of its sides does not exceed 1:5. If you need to build columns, racks, chimneys and other tall objects, then it is recommended to use this method.
- Pile strip is a support technology used to build foundations for extended structures (for example, for embankments or concrete fences).
- Pile field - it is recommended to build supports for the house using this method if you plan to build a monolithic grillage.
Design device
The finished pile field will be located at the construction site, where the supports were previously driven in accordance with the project documentation. Steel or reinforced concrete products in the structure are located in this way:
- in a checkerboard pattern - to organize a large foundation;
- rows - for driving a small number of supports.
The extreme axial lines of the rods when constructing a pile field should be set so that they are located in relation to the outer edge of the grillage being built at a distance equal to the diameter of the supports in the plan.
Creating a project
Before you make a pile field, you need to draw up a drawing, a work plan and check the soil at the construction site. It is necessary to examine the soil for the following data:
- density;
- deep freezing of the earth;
- bearing capacity;
- soil water saturation;
- groundwater depth;
- stratification of different types of land on a construction site.
The bearing capacity of one rod is simply unrealistic to calculate, knowing only what material the product is made of, since the soil resistance force is usually less than the load-bearing index of the pile. Therefore, it is necessary to carry out geodetic work in order to calculate the technical properties of the supports, taking into account the characteristics of the land in which they will be installed.
Counting technique
The initial stage of work is the calculation of the pile field. The purpose of this procedure is to analyze the distribution of rods on the site and find out how many supports need to be installed. To do this, you need to follow several steps:
- Calculate the total load that will act on the concrete base during the operation of the building.
- Determine the bearing capacity of each pile,taking into account the parameters of the building material from which the support is made.
- Divide the final load by the calculated bearing characteristic of the bar to determine the number of supports.
- Create a project that will indicate the location of the piles along the perimeter and walls of the object under construction.
To determine the total load, it is necessary to calculate the mass of the room, taking into account the specific gravity of the building materials involved and the area of the structural parts of the building.
The next step is to calculate the load using approved GOSTs and developed projects. The documents indicate that for residential buildings this figure is approximately 150 kg/m2 overlap, and for industrial facilities - 200 kg/m2. If the building is planned to be built with two or more tiers, then the mentioned technical parameter should be calculated taking into account all floors.
After that, it is required to calculate the temporary snow load, the value of which directly depends on the region where the building is being constructed. To do this, it is necessary to multiply the area of the roof of the room by the average weight of the snow layer pressing on 1 m2 of the floor surface. Next, the amount received must be multiplied by the reliability factor, which is 1, 2.
The next step is to calculate the bearing capacity of the piles, taking into account information about the characteristics of the soil on the site. When all the indicators are known, the final calculation should be made. To do this, it is necessary to divide the total mass of loads by the load-bearing capacity of the product. The result will be a number indicatingthe required number of supports on which the pile-grillage foundation should be erected.
All calculated indicators must be indicated in the project documentation.
Pile type selection
For the construction of the foundation, solid reinforced concrete products are most often used, the cross section of which is 300 x 300 mm. Such supports are used for the construction of structures of the following types:
- High and low-rise buildings.
- Industrial type facilities.
In addition, the mentioned supports are acquired when it is necessary to strengthen the pile foundation. But for the construction of massive buildings, products with a section of 400 x 400 mm are sometimes used as rods. If the floor on the pile foundation will be made of lumber, it is recommended to use piles with dimensions of 250 x 250 mm.
Square rods are most often used in the construction process of buildings placed on these types of soil:
- heaving (ground expanding in winter, so it puts a lot of pressure on the foundation in the cold season);
- peat bogs;
- boggy and silty soils;
- in areas where the ground is subject to shifts in the horizontal direction.
Sometimes builders organize a pile field from composite products, if the site has low-density and moist soil over 10 cm thick. In this case, the length of solid rods to build a reliable foundation is simply not enough. Masters even make connected supports that are immersed in the soil to a depth of 20 meters.
Performing markup
This is an important step that builders carry out before starting the installation of piles. To make markup technically correct, you need to perform the following tasks:
- Mark the baselines or contours of the foundation of the pile field on the construction site - a design diagram will come in handy for this.
- Apply markings in places where the supports will be installed. Keep in mind: each individual element will have its own drive point.
- Determine the zero mark, with which you can align the piles after installation in the ground.
Markup should be done using cast-off. This is a temporary wooden structure, with the help of which the center axles are attached. The drawing should define the points where the piles should be installed. With the help of equipment - an electronic total station - a specialist will determine the location of the supports on the construction site, and then mark these points with the help of reinforcement. Sometimes masters use a regular tape measure to perform these jobs.
The main thing is to securely install each reinforcement so that the product does not move from a given area, otherwise you will have to call the surveyor again.
Building the structure
After markup is completed, activities should begin, which include the following technological processes:
- delivery of necessary equipment;
- acquisition, transportation and unloading of piles;
- digging a pit.
The next stage is the deepening of the supports into the soil using a special constructionmachine, which is called a pile driver. The specified wizard process is performed in the following order:
- The pile driver is installed in the area where the installation points of the supports were marked, and the piles are moved using a winch installed on the machine.
- Workers help sling the support.
- The pile is lifted vertically at the point of penetration.
- The product is being fixed on the mast of the pile driver and connected to the pile driver. The next step is driving the support into the ground to a depth, the required size of which is indicated in the project documentation.
- After installation of all piles, it is necessary to align them to the set zero mark. As a rule, such work is carried out using jackhammers.
The main thing is that a design drawing be prepared in advance, since this document contains instructions with which all construction work is carried out.
Pile field acceptance
The following information is presented for acceptance of the design:
- information about the geodetic verification of clogged supports in height and in plan;
- number of hammer blows per pile.
The engineer must record the data obtained in a special journal. And if we compare the information and test results (static and dynamic), then when drawing up the project, you should set:
- the need to remove the upper parts of the piles to the specified marks;
- suitability of the installed supports and their compliance with the load-bearing capacity of the total building loads;
- needinstallation of additional piles.
Floor device
On the pile field, you can equip the flooring when the construction of the grillage is completed. In this case, the main thing is to use wooden slats to form gaps, with the help of which the structure will be protected from condensation.
For flooring, you should purchase an edged board with a thickness of more than 28 mm, but the craftsmen advise using at least 36 mm products. In addition, you need to purchase high-quality elements for fastening lumber.
The next step is laying OSB boards, since this material is the easiest way to level the floor surface. Insulation of the flooring is an important process, which should be taken care of after the completion of the arrangement of the supporting structure. Therefore, it is recommended to use mineral wool with a thickness of 20 cm or more.
Conclusion
Responsibility and care are the basic requirements that must be observed during construction. The process of erecting a residential building, the foundation of which will be built on an established pile field, is especially important, so the technique for performing these works is discussed in the article.
