Bored piles with grillage - technology. Bored piles
The durability and strength of the building depend on the quality of the foundation. It is necessary to choose the material and type of the base construction, taking into account the degree of load that the house will have on the foundation. It is important to pay attention to the depth of soil freezing, as well as soil characteristics. Monolithic tape designs are used in suburban housing construction quite often. However, sometimes preference is given to foundations on bored piles. These designs have many advantages.
The device base on bored piles
The device of the bored base is quite simple. In the wells that are drilled in the ground, it is necessary to install piles, where a monolithic grillage will be created. He will perform the basis for the house. The depth of the wells is determined based on the indicators of soil freezing in a particular area. Thus, the supports are located 1.5 m below the freezing line.This eliminates the extrusion of piles under the influence of low temperature.
The diameter of the supports depends on the degree of load, and more precisely, on the type of building material that is used in the construction of the building. It is necessary to draw conclusions with an eye on the density and composition of the soil. The device of bored piles may provide for the formation of a hanging grillage. It is relevant when the base is located on uneven terrain. Between the grillage and the soil at the same time there will be space. Bored piles with a grillage, the construction technology of which is described in the article, may have different height parameters, which allows you to create a horizontal basis for building a house.
This kind of foundation eliminates the impact on the grillage of the forces arising from the swelling of the soil. Only professionals can create a formwork of this type. Rostverk can be deepened even in the soil. To avoid deformation during heaving of the soil allows the created sand pad. Its thickness should not be less than one meter. The device of bored piles necessarily provides for the presence of holes in the grillage, sewer pipes are used for this.
When building the foundation on bored piles, several methods can be used, among them:
- with removable formwork;
- with waterproofing;
- with permanent formwork.
If on the construction site the soil is sufficiently dense, then covers are inserted into the completed wells. They are made of polyethylene film. The walls of the wells can also be laid with roofing felt. Concrete is poured inside. Impressive soil density maintains the position of the supports. But the presence of a waterproofing layer will prevent the penetration of water and violation of the structure of concrete.
When bored piles with a monolithic grillage are installed, removable formwork can be used to create supports. Fences are made of metal or plastic. 2 hours after pouring, the strength of the concrete becomes high enough so that the structure retains the desired shape. The formwork is removed in the next step.
Bored piles with a grillage, the construction technology of which should be known to you, have some drawbacks. Among them is the lack of protection of supports from exposure to water.But the technology allows you to create a sand pillow, which reduces the impact of the frozen layer. If there is a need to form the formwork of different shapes and diameters, then the pile can be given a tapered shape. When the soil is exposed to the side walls, they will be pressed in rather than pushed out.
If you decide to build a foundation with a grillage, then you can use another technology that involves the use of fixed formwork method. The latter remains in the ground and performs the role of waterproofing. For this, metal pipes, special cardboard or asbestos cement are usually used.
This approach allows you to reliably protect the supports and eliminates height differences, creating a layer of sand between the piles and walls of the well. If the groundwater is too close to the surface, the wells will fill up quickly. Therefore, before installing the supports water is pumped out by the pump. In this case, the lower part of the pipe, which serves as a formwork, is filled with waterproofing concrete per meter of height.
Bored piles with a grillage, the construction technology of which is not so complicated, can be strengthened.Reinforcement is used for this. It is also necessary in the presence of the risk of extreme loads, as well as increased shear forces. For this purpose, a framework of metal rods is used, the diameter of the latter can vary from 1 to 1.2 cm. However, triangular structures can also be used. An additional advantage of reinforcement is the formation of a solid foundation of the supports and grillage. In this case, the design acquires increased reliability and durability.
More about the method
Before starting construction of the foundation, calculations should be made and markup should be made. This determines the future boundaries of the house and the location of the main nodes. The distance between the piles will depend on the type of construction. This parameter can vary from 1.5 to 2.5 m.
To build a house on bored piles with a grillage, you should prepare:
- formwork for piles;
- concrete mixer;
- ribbed metal rods for reinforcement.
Formwork is inserted into the drilled wells. Today, cardboard pipes are available for sale. Metal formwork before installation is protected from rust with reinforced adhesive tape or bitumen.If the work is carried out on loose soil, then before installing the formwork it is necessary to form a cushion of sand and gravel, the thickness of which will be 15 cm.
Once the pipe is in the well, you need to drive reinforcing rods, between them should be maintained a distance of 7 mm. Drive them to the ground by 30 cm. To fasten the rods, you must strapping. Armature and piles should protrude above the ground. This part will be the link between the grillage and the supports.
The solution is poured into the pipe. The step between the formwork and the edges of the well can be poured with a solution or filled with sand. When a bored foundation with a grillage is built, in the next stage, you can perform formwork for the latter. It must be airy, it uses pipes for sewage.
Work with concrete
A solution is poured into the prepared formwork. After completion of the stage of hardening of concrete, you can start building a house. If we are talking about a brick or frame building, as well as the construction of the foam block or timber, then the described construction will be an excellent option. It will save money and time, and also eliminate the need to use special equipment.
The use of the natural landscape in the construction opens up possibilities for creating the original design of the site, while the buildings and plantings can be preserved. Formwork should be placed on top of piles. Inside there is an armature. There is poured concrete. The technology in this case is similar to the method for manufacturing strip foundations.
The height of the grillage should ideally be 30 cm or more, whereas the width of the structure exceeds the thickness of the walls of the building and is approximately 40 cm. Such a foundation requires a greater amount of earthwork, costs and time. If you want to build a house on this basis, you will get a reliable and high-quality foundation.
Calculation of bored piles with grillage should be carried out necessarily. In order to make the foundation strong and durable, it is necessary to determine the permissible load of one pile. Its value will depend on the size of the supports. If the support is 30 cm thick, it will withstand a load of 1.7 tons. Increasing the first parameter to 50 cm, you can exert a load of up to 5 tons.
Even a slight difference in size will affect the carrying capacity.Permissible load also depends on the material of the manufacture of supports. For example, if the piles are made of concrete grade M100, they will be able to withstand pressures up to 100 kg per square centimeter. This indicates that a square support with a side of 0.2 m must withstand pressures of up to 40 tons.
When calculating the number of piles, you should consider the bearing capacity of each support, as well as the strength of the underlying soil layer. Carrying out the calculation of the foundation on bored piles with a grillage, you must determine the allowable load bearing, which will be under the influence of compressive longitudinal load. This parameter is calculated by the formula: P = k * R * F + U * N * Fn * L. Here, the indicator of soil homogeneity is k. The resistance of the soil to the pressure of the support is R, while the size of the bottom of the pile is F.
The perimeter of the pile bottom is U. The standard soil pressure on the side supports is Fn, while the factor that determines the operating factors is N. The soil layer that will press on the side surface of the piles is L. When determining the distance between the supports, it should be noted that the maximum step is 2 m. Between the supports there should not be less than three double diameters of the supports.
Information on diameter and additional parameters of supports
The diameter of the bored piles is selected taking into account the bearing capacity of the products. For example, if this parameter is 15 cm, then the carrying capacity will be equal to 1062 kg. The support area should be 177 cm.2. The volume of concrete will be equal to 0.0354 m3. The price of such a pile is 172.05 rubles. If the diameter increases to 25 cm, then the carrying capacity will be equal to 2946 kg. The area of support will be 491 cm2, but the cost of one support is equivalent to 335.3 rubles.
Waterproofing of bored piles with a grillage may involve the use of rolled materials. Sometimes plastic or asbestos pipes are used. If you decide to use soft, fragile material, then you should additionally take care to strengthen the aboveground part. To do this, prepare a wooden casing or steel mesh.
Before you start building the described foundation for your future home, you need to consider some negative points. Among them should be highlighted the complexity of the construction of the cap. The presence of a monolithic grillage above the ground creates additional difficulties, because the space between the piles should not remain empty.You should not choose bored piles with a grillage, the construction technology of which was described above, if you plan to build a house on subsiding or swelling soils.