For the construction of baths in Russia, a columnar or strip type of foundations is often used. But a more modern option is a bored base, which is due to a number of its advantages. This option can be called ideal for sites that are on slopes or have problem soil. If the development on the territory is rather dense, then the described construction allows the construction of a two-story bathhouse without consequences for the soil and adjacent buildings.
Device features
Bored piles do not clog with force into the soil and do not damage the layers - they grow out of the ground. The work involves drilling wells where a pipe or a removable formwork is placed. The interior space is filled with mortar.
If we are talking about soft soil, then a bored foundation with grillage may be the only possible option. One of the main tasks of pillars and piles is the support on a solid layer of soil, which is not compressible and is located below the freezing line and groundwater. Such soil in some regions lies deep enough. Bored piles are able to reach such a line, holding a fairly large bath on themselves.
Piles can be installed together with a heater. The result is a more expensive but reliable design. For this, polystyrene foam is used, which has a rigid structure. It is fixed for waterproofing and covered with soil. Expanded polystyrene is an excellent shock absorber for soil heaving forces . Even the tape base on bored piles does not violate the communications established on the site earlier. True, there will be no basement in such a building, but this is not a problem for a bathhouse. Another advantage of such a foundation is a long service life - the design is ready to last more than 100 years.
Calculation
Calculation of bored piles is carried out at the first stage. For example, the width can be determined taking into account the thickness of future walls. For frame construction, there is no need to deepen the base too much, because the walls will be thin and light. If you plan to build a real Russian steam room from a bar, then the foundation will need to be done more by 40 mm to ensure even distribution of the load.
For example, the area of the support will depend on the diameter of the pile. If the last parameter is 15 cm, then the first is 177 cm 2 . With a bearing capacity of 1,062 kg, concrete is needed, the volume of which is 0.0354 m 3 . For reinforcement, you will need to prepare 3 bars, while the consumption of reinforcement per linear meter will be 7 pieces. With an increase in the diameter of the pile to 40 cm, you will need to make a support with an area of 1 256 cm 2 . In this case, the bearing capacity will be equal to 7 536 kg, and the volume of concrete used - 0.251 m 3 . Vertical bars should be used 8 pieces, per linear meter they will need 18.
As an example, consider the option of building a foundation for a house, whose weight is 60 tons. The diameter of the piles will be 20 cm. One stand will be able to support a weight of not more than 1,884 kg. If you divide 60,000 kg by this value, you get 31.84 pieces. This amount should be rounded up to an integer, which will allow you to get 33 piles. If the filling will be carried out without casing pipes, then you will have to buy reinforcement and concrete, the total cost of which will be 13,717 rubles. In order to get this value, 32 need to be multiplied by 428.68 rubles.
Marking, drilling and formwork
If you decide to build a foundation on bored piles, then for a start you will need to mark the site. Supports in the territory can be located in the form of a solid wall or in a checkerboard pattern. Sometimes they are installed under certain sections of the building. Then you can do well drilling. One will take several hours.
The most productive in Russia today are Yamoburs of Japanese and Korean production. Using them, you can build bored foundations in a short time. The installation of bored piles involves the manufacture of formwork, which is what you will do in the next step. It is necessary in order to exclude soil shedding. Under normal geological conditions, you can do without formwork, in this case concrete is poured into the created well, which facilitates the process. You will need to make formwork on the surface of the earth. As a formwork, roofing material will appear here, which folds in the form of a pipe.
Recommendations on how to choose products
You can choose the diameter of the bored pile, taking into account the above calculations. The supports must be durable and strong so that their bearing capacity is high enough. But do not be too zealous, establishing supports on every square meter.
Piles you can do with your own hands. They are made on the spot, so there is no need to worry about the need for an area for storage. Supports are quite common today, the bases of which are expanded to 50 cm, which is facilitated by technological methods. They allow you to increase the bearing capacity of products up to 5 tons. On such a foundation, you can build a building of brick.
Pillow work and reinforcement
Pillow for the foundation - required. It is made of crushed stone, sand or concrete mix. The substrate is compacted, and after the well is filled with basic material. In order to ensure the strength of piles, it is possible to use reinforcement, which, with the help of a grillage, fits into a single structure.
In order to make the piles strong, reinforcing cages are made for them. To do this, you need 12 mm rods that are connected to each other. You can also apply ready-made triangular frames, which are purchased for floor beams.
Piling
Bored piles are installed in the next step. It is necessary to deepen the products by 1.5 m more in relation to the freezing line of the soil. You can determine the freezing depth in a certain area on the geological map. The prepared well with formwork and reinforcement is poured with M-200 brand concrete.
To eliminate voids, the reinforcement is raised several times inside the well. If you use technology with expansion of the base, then the formwork must be raised by 30 cm after pouring the first portion of the mortar, which will allow the concrete to fill the base. Further construction with this technology can only begin in a few days. Supports should be waterproofed with bituminous mastic or roofing material to prevent destruction.
Features of waterproofing
Bored piles are waterproofed to prevent the absorption of cement milk. The walls of the wells are covered with a durable plastic film or roofing material. The latter option is preferable. If you plan to use the film, you should weld it and make a cover out of it, which will act as an excellent barrier to the foundation. This method is suitable for strong soil. In other cases, cardboard, metal or asbestos-cement pipes can be used.
More about fill features
If you plan to use the technology described in the article, bored piles are best made by pouring concrete from a mixer. So in a day you can deal with large volumes. The foundation is poured with quick-hardening cement, which should be diluted in small portions. You need to do this as soon as you start tamping the previous layer.
Wells can be filled with concrete mixed with stone, limestone, cobblestone or sandstone. Such a filler must have high strength. This refers to rubble stone. In order to ensure better compaction of the mortar during the installation of bored piles, a special drill should be used, which creates mechanical vibration. During construction, this will eliminate even the smallest voids in concrete. To improve the result, it is better to use high-quality hydraulic concrete, which is fed into the mold by a hydraulic machine that provides the desired pressure level.
Frames for piles: what you need to know
Frames of bored piles can have a length of up to 12 m. The diameter of the longitudinally located reinforcement varies from 8 to 42 mm. The production frame has a diameter that is equal to the limit of 250 to 800 mm. The working whips of the reinforcement inside the frame are used in an amount of 4 pieces. The core is winding reinforcement, the diameter of which varies from 12 to 14 mm. The winding pitch can vary from 100 to 300 mm.
Finally
Starting work on a bored foundation using hand tools and pits, you should be prepared for the fact that these devices have limitations in diameter. For example, without any problems you can drill a hole up to 40 cm. Most manufacturers of drilling tools have this tooling.
But if you plan to use augers and cutters, then their diameter can be 50 cm, but they are produced by only a few manufacturers, whose goods you can find on store shelves. If the well has a larger diameter, then you will have to dig a pit manually. The formwork is installed inside, and after the formwork it will be necessary to control the quality of the fill and carry out external waterproofing.