For the construction of baths in Russia, a columnar or tape type of foundation 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 areas that are on slopes or have problematic soil. If the development on the territory is quite dense, then the described design allows the construction of a two-story bath without consequences for the soil and nearby buildings.
Device Features
Bored piles do not drive into the soil with force and do not damage the layers - they grow out of the soil. The work involves drilling wells, where a pipe or removable formwork is placed. The interior space is filled with mortar.
If we are talking about soft ground, then a bored foundation with a grillage may be the only possible option. One of the main tasks of pillars and piles is to support a solid layer of soil that is not compressible and is located below the freezing line andground water. Such soil in some regions lies quite deep. Bored piles are able to reach such a line by holding a sufficiently large bath on themselves.
Piles can be installed together with insulation. As a result, it is possible to obtain a more expensive, but reliable design. For this, polystyrene foam is used, which has a rigid structure. It is fixed on waterproofing and covered with soil. Styrofoam is an excellent shock absorber for soil heaving forces. Even a tape base on bored piles does not violate the communications installed on the site earlier. In such a building, however, there will be no basement, but for a bath this is not a problem. Another advantage of such a foundation is its long service life - the structure is ready to serve for 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 made 40 mm larger to ensure even load distribution.
For example, the area of support will depend on the diameter of the pile. If the last parameter is 15 cm, then the first is 177 cm2. With a bearing capacity of 1,062 kg, concrete will be needed, the volume of which is 0.0354 m3. For reinforcement, you will need to prepare 3bar, while the consumption of reinforcement per linear meter will be equal to 7 pieces. With an increase in the pile diameter to 40 cm, you will need to support an area of 1,256 cm2. In this case, the bearing capacity will be equal to 7,536 kg, and the volume of concrete used will be 0.251 m3. Vertical bars should be used 8 pieces, per linear meter they will need 18.
As an example, consider building a foundation for a house weighing 60 tons. The diameter of the piles will be 20 cm. One rack will be able to withstand a weight of no more than 1,884 kg. If you divide 60,000 kg by this value, then you get 31.84 pieces. This number should be rounded up to a whole number, which will give 33 piles. If the pouring is 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 must be multiplied by 428, 68 rubles.
Marking, drilling and formwork
If you decide to build a foundation on bored piles, then first you will need to mark the site. Supports on 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. Next, you can start drilling wells. One will take several hours.
The most productive in Russia today are yamoburs of Japanese and Korean production. With the help of them, you can build bored foundations in a short time. The installation of bored piles involves the manufacture of formwork, which you will do in the next step. It is necessary in order to prevent shedding of the soil. Under normal geological conditions, you can do without formwork, in which 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 act here, which is rolled up 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 don't be too zealous, installing supports on every square meter.
You can make piles with your own hands. They are made on site, so there is no need to worry about the need for storage space. 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 out of bricks.
Cushion work and reinforcement
Cushion for the foundation - required. It is made of crushed stone, sand or concrete mix. The substrate is compacted, and then the well is filled with the base material. In order to ensure the strength of the piles, you can use reinforcement, which is knitted into a single structure with the help of a grillage.
To pileturned out to be strong, reinforcing cages are made for them. For this, you need to use 12 mm rods that are connected to each other. You can also use ready-made triangular frames, which are purchased for floor beams.
Installation of piles
The bored piles are installed in the next step. It is necessary to deepen the products by 1.5 m more in relation to the soil freezing line. You can determine the depth of freezing in a certain area on a geological map. The prepared well with formwork and reinforcement is poured with M-200 concrete.
To eliminate voids, the reinforcement is lifted inside the well several times. If you use technology with base expansion, then the formwork must be raised by 30 cm after pouring the first portion of the solution, which will allow the concrete to fill the base. Further construction with this technology can be started only after a few days. Supports should be waterproofed with bituminous mastic or roofing material to prevent destruction.
Waterproofing features
Bored piles are waterproofed to prevent the absorption of cement laitance. The walls of the wells are covered with a durable polyethylene film or roofing material. The latter option is preferable. If you plan to use a film, then 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 solid ground. In other cases, cardboard, metal or asbestos-cement pipes can be used.
Additionally about fill features
If you plan to use the technology described in the article, it is better to make bored piles by pouring concrete from a mixer. So in a day you can handle large volumes. The foundation is poured with fast-hardening cement, which should be diluted in small portions. This must be done as soon as you start ramming the previous layer.
You can fill wells with concrete mixed with stone, limestone, cobblestone or sandstone. Such a filler should have high strength. This applies to rubble stone. In order to ensure better compaction of the solution when installing bored piles, a special drill should be used, which creates mechanical vibration. During construction, this will eliminate even the slightest voids in the 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 level of pressure.
Pile frames: what you need to know
Carcasses of bored piles can have a length of up to 12 m. The diameter of the longitudinally arranged reinforcement varies from 8 to 42 mm. The production frame has a diameter that is equal to the limit from 250 to 800 mm. Working whips of reinforcement inside the frame are used in the amount of 4 pieces. It is based on coiled reinforcement, the diameter of which varies from 12 to 14 mm. The winding pitch can vary from 100 to 300 mm.
In conclusion
When starting work on a bored foundation using hand tools and hole drills, you should be prepared for the fact that these devices have diameter limitations. For example, without any problems, you can drill a hole up to 40 cm. Most manufacturers of drilling tools have such equipment.
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 products you can find on store shelves. If the well will have a larger diameter, then you will have to dig the hole manually. The formwork is installed inside, and after stripping it will be necessary to control the quality of the pouring and carry out external waterproofing.
