How to make a bored foundation with your own hands. Do-it-yourself bored foundation. Application of bored technology in private construction

Bored piles- variety pile foundation, which involves constructing piles by drilling holes in the ground, followed by their reinforcement and concreting. The result is a strong monolithic foundation capable of absorbing heavy loads not only from the erected building, but also from lateral soils.

There are several classifications of bored supports, which are described in detail in SNiP 2.02.01-83 and SP 50-102-2003. The documents indicate the types of piles, requirements for them, and construction technologies. For private construction, two types of bored supports are used:

Cylindrical. They have the same diameter throughout the support body.
With a widened support sole - the heel. The installation of heel piles is a complex process that is impossible without special equipment - drill columns with cutters. In dense soils, an explosive method is used to create widening.

When building cottages with your own hands without hiring a contractor, supports with a widened heel are not used. Primitive widening can be arranged if casing pipes are used, but it has nothing to do with the calculated heel, which is carried out during the construction of multi-story buildings in accordance with SNiP.

Foundations on bored piles are used in multi-storey and private construction in the following cases:

In densely built-up conditions, when it is impossible to dig a foundation pit for a different type of foundation.
On swampy, weak soils, when dense soil is located at a depth of more than 1 m.
In areas with difficult terrain.
When constructing houses using heavy building materials (granite, ceramic bricks).
If there is a threat of flooding of the site, near water bodies, with high groundwater levels.
In the absence of data on hydrogeological surveys on the site.

Pros and cons of a bored foundation

A bored-type foundation has both advantages and disadvantages inherent in all pile foundations. Among benefits note:

versatility, suitable for soils with any characteristics;
high load-bearing capacity;
simple calculations and diagrams, you don’t have to order a project;
service life of at least 100 years;
installation can be done with your own hands, without the help of contractors;
no need to dig a pit;
minimal loads on the soil of neighboring areas;
the possibility of preserving the improvement of the territory;
low cost compared to other types of foundations.

TO shortcomings designs include:

relatively large volume concrete works;
the need to strengthen wells in loose soils;
labor-intensive installation process;
impossibility of installing a basement in the house.

Bored or screw piles: which is better?

Having decided to build a foundation on pile supports, owners of building plots do not know which piles are better to use: screw or bored piles. Let's compare both options:

Evaluation criterion	Bored piles	Screw piles
Load-bearing capacity of a pile with a diameter of 50 cm	Can withstand 4 tons	Withstand 1.5 tons
Resistance to corrosion and aggressive environments	High	Low
Range and sizes	Unlimited	Limited to existing sizes
Use in soils	In all soils except rocky ones	Not used in rocky, swampy, alkali soils
Labor intensity of installation	Medium: drilling, reinforcement, concreting required	Low: piles are screwed into the ground
Installation time	Depends on concrete work	In any season
Life time	At least 100 years	From 25 to 50 years

Price screw piles depends on the size, the metal used to produce them and the processing method. The price of bored supports is determined as the sum of the cost of casing pipes, reinforcement and concrete.

As can be seen from the comparison table, bored supports are more durable and cheaper. However, their installation requires significantly more effort than the installation of screw piles.

Calculation and layout of bored piles

To carry out the calculation of a bored foundation, it is first necessary to collect the following initial data:

Study of soil characteristics on the site. If hydrogeological surveys have been carried out, then data about them can be found in the project. If there is no information about the survey, it is necessary to carry out pitting. A pit is a vertical exploratory excavation 1.5-3 m high, used to study layers and their characteristics. The purpose of pitting is to determine the depth of load-bearing soils. You can do the boring yourself using a regular garden drill.

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Sergey Fedorov

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Exploratory drilling is necessary not only to detect load-bearing soils, but also to determine their thickness.

The characteristics of soils that are determined during pitting can be found in SNiP 2.03.01-84, 2.05.03-84 or 2.06.06-85.

Collection of loads on the base. They are defined as the sum of all structural elements of the house (from the roof to the foundation) and temporary loads. To calculate loads, a design and estimate for materials is required. It is best to calculate loads using special programs, for example, Foundation, Base 6.2, etc. When building a small lightweight building, you can use a calculator like “Weight-Houses-Online v.1.0”. Load calculations can also be made independently, based on SNiP 2.01.07-85.

Knowing the characteristics of the soil and the total load that will be exerted on the pile foundation, you can begin to calculate it using the following algorithm:

Calculation of bearing capacity. To simplify the task and not make complex calculations, we suggest using a table that shows the bearing capacity of bored supports of different diameters depending on the type of soil:

The table shows load-bearing capacity data calculated based on the use of class B22.5 concrete for bored piles. If you plan to use concrete whose class is lower, the load-bearing capacity of the pile will decrease. For example, a 30 cm support made of B22.5 concrete in hard sand will bear 3179 kg, and the same pile made of B17.5 concrete is 30% less, i.e. 2225 kg.

Selecting a section (diameter). When choosing the optimal diameter, it is necessary to take into account that piles of large cross-section will require not only a lot of concrete mixture, but wider wells and casing pipes. Too narrow supports are easy to install, but their number will be greater. For 6x6 houses, it is recommended to choose a diameter of 15-25 cm. For cottages made of light materials - 30-40 cm, for those made of heavy materials - 40-50 cm.
Number of bored piles. To calculate the number of pile supports, it is necessary to divide the total load by the bearing capacity of a pile of the selected diameter.
Distance between piles. The distance can be calculated using the formula:

l is the distance between the bored supports;
P is the load-bearing capacity of the pile;

Without using the formula, the pitch of pile supports can be determined as follows: the distance between the elements should not be more than 3 of their diameters. It is worth remembering that the higher the mass of the structure, the smaller the pitch of the piles. The minimum distance can be 50 cm.

Depth or length of piles. Determined based on the depth at which the load-bearing soils are located. The depth of driving piles should be below the freezing level, even if the bearing layers are located higher. Information about the freezing depth for your area can be found on the Internet.

Calculation example: The construction of a cottage takes place in the Moscow region on medium-density sand. The size of the house is 10 x 10 m, the total load is 60 tons. To construct the foundation, we select piles with a cross-section of 30 cm. Based on the table, we find that the load-bearing capacity of the pile will be 2473 kg. The number of supports will be 60/2.4 = 24 pcs. The distance between the piles will be 60-90 cm. The length of the piles, taking into account the freezing level for the Moscow region and the depth of the supporting layers, is 2.2 m.

To draw up a diagram of the location of pile supports, it is necessary to take into account that the piles should be located at each corner of the house, along the load-bearing walls with the selected pitch, as well as under the entrance group and heavy structures.

Construction of a bored foundation with your own hands

Unlike other types of piles, bored supports are not regulated by GOST. The technology for their installation is prescribed by SNiP 2.05.03-84. The document specifies the following installation methods:

concreting wells with or without casing;
immersion of formwork filled with concrete;
continuous concreting with camouflage heel;
immersion of a monolithic core into the well.

Not long ago, CFA technology appeared, which consists of concreting piles using a hollow drill with a drill through which concrete is supplied. Due to the fact that most owners of suburban areas do not have complex tools for drilling and concreting, we will consider the simplest method of installing bored piles - concreting with or without a casing.

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Sergey Fedorov

Professional builder. 18 years of experience

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IN winter period work on the installation of a bored foundation must be carried out at an air temperature of at least -10 C.

The installation of pile supports can begin after marking the future foundation. Marking is carried out using poles and twine. For a future shallow-type strip or monolithic foundation, a trench or foundation pit 0.5 m deep is dug. Holes are made in the places where wells are drilled.

Step-by-step instructions for installing a bored foundation:

Drilling wells and installing casing pipes

Drilling is carried out with a manual auger or a gas drill. The size of the auger nozzle depends on the diameter of the well. A 10-20 cm cushion of coarse sand is poured onto the bottom of the well. Is it necessary to install a bored foundation using casing pipes? According to technology, casing pipes can be permanent (remain in the well) or removable. It is also possible to install the base without casing pipes. The advantages of using casing strings include:

preventing the well wall from collapsing;
waterproofing concrete piles;
simplified installation of reinforced frame;
more simple fill concrete.

The use of casing pipes also has disadvantages:

increase in the volume of work;
rise in price of the foundation.

The cost of casing pipes depends on the material and size. It is best to use plastic or asbestos cement pipes, which are immune to corrosion. The length of the pipes should be 30-50 cm greater than the calculated length of the piles. Installation of pipes is required in loose, viscous, swampy soils. In clayey and dense loamy soils, casing pipes can be dispensed with. In this case, the walls of the well are lined with waterproofing or roofing felt to create waterproofing.

When using casing pipes, the products are immersed into the well by pressing or driving in with a sledge hammer. The pipe must be installed strictly vertically inside the well. Position is controlled building level. The permissible deviation for a 2 m pipe is no more than 1 cm to the side. The gap between the well wall and the casing pipe is filled with soil.

Reinforcement of bored piles

Reinforcement is necessary to withstand compressive loads acting on the pile from all sides. The reinforcement for bored piles is tied into a spatial reinforcement frame. The number of longitudinal reinforcement bars is 4 or 6. Vertical bars are installed every 30-40 cm. The diameter of the A3 class reinforcing bars used is 15-20 mm. The length of the rods should be 0.5 m longer than the length of the casing pipes. The reinforcement used for the reinforced frame must comply with GOST 5781.

Knitting of reinforcement cages is carried out using annealed wire with a cross-section of 1-5 mm. For fixing the rods, clamps or 90 mm plastic tubes are best suited. The frame is made using an arm bender or a knitting gun as follows:

the reinforcement is cut to the required length
holders for longitudinal rods are mounted;
4 or 6 rods are positioned in space using a holder;
Vertical rods are mounted with the selected pitch using wire and clamps.

Expert opinion

Sergey Fedorov

Professional builder. 18 years of experience

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Reinforcing waste, as well as rusty and dirty reinforcement, should not be used to reinforce bored piles.

The finished reinforcement cage is lowered into the well and installed there in such a way that the reinforcement does not come into contact with the walls of the casing pipes.

Concreting of bored piles

Class B22.5 concrete is used for concreting. For light buildings, the use of concrete mixture of class B15...17.5 is allowed. Concrete in composition and physical and mechanical properties must comply with GOST 19804.2-79, 10060.0-95, 10060.4-95 and 12730.0-78. At self-production concrete mixture must be strictly followed.

The best option is to order ready-made concrete with delivery. In this case, it is advisable to order an ABS with a hose of the required length, through which the mixture will be supplied to the wells. Also note that concreting each pile takes 10-20 minutes, and the free ABS parking time is 1 hour. For the time that the mixer spends on your site in excess of this norm, you will have to pay extra separately.

Pouring is done by supplying concrete to the wellhead through a funnel lowered down. Concrete is fed into the well in portions: when a layer of 30-50 cm is formed, it is necessary to stop pouring and perform vibratory compaction. Then the next portion is poured and compacted. The pile head is formed by pouring casing to the top edge. Concrete hardens within 7-10 days.

The structure of the heel is the base of the bored support.

Heel is a widening of the base of the pile, which allows you to increase the load-bearing load by 5-10%. When arranging a pile foundation with your own hands, you can make a widening in one of two ways:

expansion of the soil at the wellhead using reinforced compaction followed by pouring the concrete mixture;
use of casing pipe with widening at the bottom.

In the first method, it is impossible to assess the quality of the resulting heel, and in the second, labor intensity increases significantly due to drilling a wider well. In most cases, when building a private house, even of a large mass, it is not advisable to widen it.

Trimming casing pipes and fittings

Pruning is done with a grinder. The reinforcement bars should protrude from the pile head, but be equal in height. Using protruding reinforcement, the connection will be made pile foundation with the ground part.

Construction of the ground part of the foundation

There are several options for foundations supported by a bored foundation:

Pile-monolithic. Combined type of base, in which on top pile field a monolithic slab is poured. It is used mainly on dense soils and for buildings with a large mass. Advantages: highest load-bearing capacity. Disadvantages: large volume of concrete work and high cost.
Pile-tape. Strip foundation on piles - best option For country house. A monolithic foundation strip, poured using formwork, rests on bored piles, transferring up to 40% of the weight of the house to the supports. Advantages: ease of implementation, low cost, reliability. Disadvantages: on swampy soils, it is necessary to install a hanging strip foundation, which is almost impossible to calculate and implement independently.
Pile-grillage. The design resembles a pile- strip base, but instead monolithic tape The load from the structure is taken by the grillage. A foundation with a grillage is perfect for small country houses, bathhouses, and outbuildings. Advantages: simple installation, the ability to independently arrange a metal hanging grillage. Disadvantages: relatively low load-bearing capacity.

Posted By: 09/20/2016

In we told how we made the reinforcement frame of the piles. Today we will continue to make bored piles with our own hands and answer common questions based on our personal experience:

— Which permanent cast-off for piles should I choose to save my budget?

— How much cheaper is it to make a roofing felt jacket for piles than to use asbestos-cement ones?

— How much does it cost to rent a drill machine in Moscow Region and how long does it take to drill holes for piles?

— How to insert a roofing material jacket into a hole for piles so that it does not curl up?

— How to carefully pour concrete into piles without a concrete pump?

— How much does it cost to rent a deep concrete vibrator?

— How much does it cost to fill piles, what is the price of renting a mixer in Moscow Region?

— What concrete should I use when pouring?

— How much does one self-made bored pile cost?

We continue our construction, namely we make bored piles for our foundation with a grillage.

In the first part we talked about how we prepared for our future bored piles. In this part we will pay attention to the jacket for the reinforcement frame made of roofing felt, drilling holes for the piles, and talk about the sand cushion and concreting the piles.

So, the first thing was to decide on permanent formwork for the piles. We chose the simplest and most economical option - shirts made of roofing felt. You may often see recommendations to use asbestos-cement cost about 3000 rub. per piece for our pile diameter of 30 cm. But this would have a rather strong impact on the budget, which we are trying not to spread too thin.

As a result, looking ahead a little, I will say that we did not regret it at all, choosing a simple and economical option. We needed to prepare roofing felt jackets for 36 piles 3 meters long, on which our small strip grillage will be located. During the work we used Roofing felt RKP-350, 1 m wide and 15 m long. Thus, 1 sheet of roofing felt went to 5 piles of 3 meters each. The price of such material in one of the well-known hypermarkets at that time was 285 rubles. per roll. For permanent casting of the piles, 8 rolls were purchased for the amount of 2280; the remnants also found their logical use, but more on that later.

The next step was to drill holes for our piles. All these places were marked with pegs. All the markings were taken from ours, which is how we build our house with our own hands.

The drill machine started its activity successfully, but in the process we encountered bricks and floor slabs in the soil, which we did not expect at all. I even had to change the nozzle because... the machine could not cope with the task. Another unpleasant moment was the spring that we stumbled upon while drilling. Why did we decide that this was a spring, and not groundwater? Because it was only in one pile hole, and groundwater would usually become noticeable in many. We were lucky, the spring was at a depth of 3 meters, so we simply covered it with clay and sand. As a result, we drilled 36 holes for piles in 7 hours with minimal interruptions. The price of all this pleasure is 13,000 rubles. for a 7 hour shift. This is the average price today for renting a drilling machine in the Moscow region (in this case, the city of Lobnya).

As soon as the holes were made, we immediately took measurements and then filled the sand cushion. The drill machine made holes for us about 3.3 meters deep. We poured about 30 cm of sand into the bottom of the holes for the piles, occasionally spilling it with water. The cost of 1 cubic meter of sand according to Moscow Region was 600 rubles, we ordered 5 cubic meters, the price was 3,000 rubles, about half was left. We plan to use the remains for a sand cushion for the foundation.

Now we had a very important task ahead of us - to insert the reinforcement cage and roofing felt jackets into the holes for the piles. We have already heard that for many people the roofing material curls up and it is difficult to straighten it, but, to be honest, we did not encounter any particular difficulties. Although, having tried to tie our 3-meter shirt with tape, as many people advise, we did not get particularly pleasant results. The tape did not stick well to the roofing felt and was completely unable to hold our colossus. In general, we simply carefully rolled our prepared roofing felt into rolls that very much resembled rolled carpets, and then inserted them into the holes for the piles. After which they began to straighten our shirts in a slightly suspended state. As a result, our shirts simply hung thanks to the long self-tapping screws inserted into the ground from the inside, which held them in place. To give rigidity to our structure, we wrapped the upper part of the shirt with the remains of roofing felt. It turned out, in our opinion, very well... The next step is to insert the prepared reinforcement cage from our future 36 piles.

Now we are ready to pour the concrete. But before calling a mixer (or in other words, a concrete mixer), we built the following structures in order to carefully pour concrete into the piles without using a concrete pump, which would significantly increase the cost of our pouring. By the way, renting a concrete pump costs about 15,000 rubles. per shift.

Thanks to these homemade tricks, we saved more than RUB 10,000. for our family budget, which is very nice, isn’t it? =)

On a certain day, a mixer with a 4-meter tray arrived to us. We placed our homemade device No. 2 in the concrete mixer tray, and structure No. 1 in the hole for the piles. The homemade container was inserted inside the roofing felt. Now we were completely ready to pour the concrete.

Just before we start pouring, let’s tell you a little more about the 3-meter deep concrete vibrator, which we rented for 700 rubles. per day. It is used at the time of pouring and immediately after it. The better you vibrate the concrete, the denser it will be, and therefore stronger. So don’t save your energy, call help when pouring, and you will definitely be satisfied with the result.

So let's continue. A concrete mixer came to us and, with the help of our homemade devices and a construction vibrator, we safely poured all 36 piles. By the way, to fill the piles we needed about 7 cubes of concrete, 1 cube was used to fill the entrance, but we will talk about this in one of the following articles. 1 cubic meter of concrete in Moscow region with delivery cost us 3,960 rubles. Accordingly, the price of the entire fill, excluding the entrance, is 27,720 rubles. During the work, we used concrete grade 350. Although we recommend concrete for the foundation not lower than M250, we still decided to go with M350. Such concrete has high strength, frost resistance and a high thickening rate, so it is recommended to be used when pouring foundations, floor slabs and load-bearing supports.

After the piles were poured, all we had to do was put them in order, namely, remove excess concrete using a crowbar. After adjustment, the tops of the piles began to look great, we were pleased with the result!

At the finish, we covered the tops of the piles with black bitumen mastic, waterproofing for the foundation (price 233 rubles). It is still a controversial issue whether this should have been done or not. To be honest, we still haven’t found the exact answer...

And now the most important thing! After calculating all the costs, it became clear that the cost of making 36 bored piles with your own hands is approximately 70,000 rubles. taking into account the rental of machines, tools, purchase of materials and prepared reinforcement frame. Thus, the cost of one 3-meter pile for the foundation is about 2,000 rubles, respectively, plus/minus...

To summarize, I will say this, we are satisfied with the result, it really pleased us. And, of course, if you want to watch a video on how to make bored piles with your own hands, then watch it right now on our YouTube channel, do not forget to like, comment and subscribe to the channel.

And now, bye, bye and successful construction.

Best wishes,

Yana and Zhenya Shigorev

During the construction of a house, problems may arise due to the presence of various communications near the building. In this case, it will be impossible to use a traditional strip foundation, so a bored foundation should be built.

It is a powerful structure, but when performing it, it is important to adhere to the permissible vibration so as not to adversely affect the foundation of the neighboring building. To prevent destruction of objects, it is necessary to use a foundation made of piles.

Properties of the structure

Such a foundation is suitable for large buildings that place large loads on the foundation

This foundation allows the construction of buildings that will be subject to high loads. A positive property of such a base is its noiselessness.

To equip a strip foundation with bored piles, you first need to make recesses into which they will then be immersed different designs made of metal.

After this, the wells are filled with cement mortar. For high-quality drilling, you must have casing pipes. They must be up to three meters long. This pipe must have a cutting tip located in the first section on the flanges from the bottom. The process with such a pipe is carried out thanks to constant rotational movements.

What the foundation of the house will be like depends on the condition and properties of the soil on which the construction is planned.

Positive characteristics

The advantages of a foundation made on bored piles include:

buildings nearby will be completely safe;
low level of vibration shocks;
there is no need to get rid of excess soil when constructing a foundation from bored piles;
ease of installation;
Suitable for constructing houses or other buildings on various types of soil.

The structure is united by a grillage

In the bored method, the foundation is made at minimal cost.

Where it is not possible to dig down to compacted soil, it is necessary to use special pillars.

In order to combine everything into a monolithic structure, a grillage should be used.

This is a special base tape that connects the tops of the piles.

Types of piles

The difference between piles and other devices used to make foundations lies in the properties of interaction with the soil.

Due to the frictional forces occurring between the soil and the wall, the load from the pile is transmitted in several ways through the lower end and side surface.

Considering which structural part is included in the work, bored piles are divided into two categories:

racks;
hanging.

When using posts, install them so that they rest on firm soil. The second option involves a hanging structure that receives load from pressure from nearby soil.

For a country house that is being built in unfavorable conditions, a monolithic slab on bored piles is required.

It is impossible to carry out a bored foundation without classification and correct various calculations. All of them are contained in SNiP - these are established standards. They contain important data and all the necessary parameters.

The procedure for performing preparatory work

You can pour concrete without formwork if the soil is dense

It is possible to build a strip foundation on bored piles all year round, which is a big advantage. To successfully complete all work, it is important to monitor the accuracy of all measurements and must adhere to established rules. There is a construction technology for this.

First, calculate the width of the future base, which depends on the thickness of the walls of the house or bathhouse. A frame structure does not require a solid foundation, since the walls are thin and light. To build from timber, you should use a bored foundation. Make it 30 - 40 cm wider so that the load is uniform.
Mark the area where the piles will be located. Their placement can be completely different.
Drilling a well should be done using drilling machines, which will greatly simplify the process.
Production of formwork. This should be done if the soil is loose. But when good conditions You can skip it by pouring the solution directly into the well. This greatly simplifies the process.
Pile selection. Select durable and high-quality parts. Thanks to such piles, the amount of excavation work will be reduced. Piles should not be installed too often. You can make them yourself without leaving the construction site. The construction of a bored foundation is often used, the base of which is expanded by 50 cm.
Piles have the ability to withstand loads of up to 5 tons. On such a foundation it is possible to erect a structure with all the additional architectural delights.

The material for making piles can be different, it all depends on the soil located on the site.

Installation of a bored foundation

After completing all calculations and marking the site, it is necessary to carry out operations for the construction of piles and their subsequent combination. Let's look at this sequence using the example of making a pile; to do this, you must perform the following steps. For more information about installing a bored foundation on difficult soils, watch this video:

Recently, pile foundations with the use of insulation have become widespread. Expanded polystyrene is used for this, since its properties can interact with the soil, which significantly simplifies the construction technology.

A bored foundation is a type of pile foundation. Piles as a foundation for the construction of a building are used where the construction of a conventional buried foundation is problematic: on peat bogs, in areas with very high level groundwater, or on weak mobile soils with very deep layers of strong soil. The bored foundation got its name due to its implementation technology: piles are made by pouring concrete into holes drilled in the ground.

Advantages and scope

The advantages of bored foundations include:

Possibility of construction in areas with weak and highly heaving soils;
Low cost of work;
Short deadlines for completing the foundation;
Low labor intensity and the ability to make a bored foundation with your own hands without the use of special equipment.

The disadvantages include the impossibility of arranging a basement and insufficient thermal insulation of the lower part of the building.

The scope of application of bored foundations is private low-rise lightweight construction: frame and wooden houses, bathhouses, gazebos and garages, country houses from light materials. A bored foundation with a floor beam (grillage) can withstand more severe loads. It is also advisable to choose this type of foundation for construction in areas with large elevation differences.

Design

The design of a bored foundation is extremely simple: using a drill, holes are made in the soil with a depth of at least 1.5 meters. The diameter of the wells is determined by calculation and is in the range of 15-40 cm. If necessary, the walls of the wells are reinforced with formwork, reinforcement is installed to prevent vertical deformation, and filled with concrete. Depending on the type of structure, grillages are laid on top of the piles or walls are erected immediately.

Execution technology

They carry out a project containing calculations of the number, depth and diameter of piles. They mark the site: determine the axes of the future building, select the first corner and hammer a metal rod into it. A string is tied to the rod, and using a protractor, two adjacent walls are laid out perpendicularly. Having measured the outer distance, mark the second and third corners, and using string and a protractor, determine and mark the fourth corner. Along the trajectory of the walls at the calculated distance, the places for drilling wells are marked.

Using special equipment or a hand drill, wells are made; their depth and diameter are determined by calculation. In this case, to make a more durable foundation, a drill is used, which has a plow at the end and allows the base of the wells to be expanded to form an expansion of the support. When drilling manually, use a level attached to the drill - check the position of the drill after each revolution and, if necessary, level it.

If the soil crumbles during drilling, formwork is performed. The simplest method, which also provides waterproofing, is roofing material rolled along the diameter of the well. The formwork can also be made from narrow boards or cement pipes.

The piles are reinforced using vertical bars of the design cross-section. The rods must be connected at some distance from each other using transverse rods, tying them with wire. If it is planned to lay grillages, the reinforcement is brought to the height of the grillage for better connection of the structures.

The prepared well with formwork and reinforcement is filled with concrete grade no lower than 200, look for it on the website. To remove voids, the reinforcement is lifted several times inside the well. If a technology with expansion of the base of the piles is used, then the formwork after pouring the first portion of concrete must be raised by 20-30 cm, which will allow the concrete to fill the base of the pile.

Further construction with this foundation technology can begin in a few days. Piles must be waterproofed with roofing felt or bitumen mastics to avoid destruction of the foundation.

Advantages

Economical. Requires less materials, namely concrete and reinforcement, compared to strip and slab foundations.
Does not require the manufacture of removable formwork. Permanent formwork is used, the production of which takes a small amount of time.
A foundation made from bored piles can easily be made independently without the use of special equipment or hired labor.

Flaws

Unlike a strip one, it is not possible to make a cellar and a basement floor.
A more detailed design is required in contrast to strip and slab.

Average service life columnar foundation from bored piles: 150 years.

Design of a columnar foundation made of bored piles

Calculated total weight future home.
We carry out soil examination (test drilling). We find out the bearing capacity of the soil, the groundwater level (GWL) and the depth of soil freezing (GFD).
We calculate the number of pillars of our foundation and their location around the perimeter of the house. The calculation will depend on 2 factors:

The poles must carry the full load of the house. The calculation takes into account the bearing capacity of the soil. In order to increase the area of the surface resting on the ground, a widening is used at the bottom of the post (the average heel diameter is 400-600 mm).
The distance between the pillars should be within 1-3m (average value 1.5-2m).

Drilling of the wells

We drill wells for piles. In this example, we will make the diameter of the holes 25 cm to a depth below the freezing depth for the given area. Let’s assume that our freezing depth is 1.5 m, therefore, we will drill to a depth of about 1.7 m.

To calculate the depth of soil freezing, you can use our calculator: Calculation of the depth of soil freezing. © www.site

For drilling, you can use a TISE drill with a diameter of 25 cm, a garden drill with a diameter of 25 cm, or automated equipment.

Another important point. You can drill all the wells at once. But in some cases, it is advisable to drill one well at a time and immediately pour the concrete mixture (concrete). This is due to weather conditions in the form of rain or high groundwater levels. Water will wash away the soil of the well walls, as a result of which it will crumble, and we do not need this at all.

We make widening at the bottom of the wells

What is it for. By widening the well, a heel of the pillar will be formed, which will perform 2 tasks: increasing the bearing capacity of the pillar and preventing the pile from being pulled out by tangential forces during the freezing of heaving soils.

Work plan. For this task, you can use a TISE drill specially designed for this purpose. It will allow you to make a widening with a diameter of 40-60 cm. But it is worth noting that in dense soil it is very difficult to work with this device. Therefore, it is advisable to check everything during test drilling during the design of a columnar foundation.

There is an alternative and inexpensive way to make the widening using a modernized bayonet shovel. To do this, it is necessary to trim the edges of the shovel blade so that the working area is within 10 cm. Well, lengthen the handle of the shovel if necessary. In order to lift the soil from such a widening, you can use some kind of device, or simply drill deeper and shovel all the soil from our widening into this depression. The main thing is not to forget to compact our “burial” later.

Creation of permanent formwork from roofing felt

1. In this example, we will use the most economical option, namely roofing felt, as formwork for a bored foundation.

We prepare a piece of roofing felt of the length we need. In our example, we need a piece 2 m long (1.7 m underground – 0.3 m widening without roofing felt + 0.3 m above the ground + 0.3 m margin for level trimming). We twist the roofing felt of the diameter we need (25cm) into a pipe. For this task, it is better to use a certain template onto which we will wind the roofing material. In our example we have a metal pipe. You can make the template yourself, showing ingenuity. There are many options.

After the roofing felt has been rolled up (2 layers thick), it is necessary to secure the resulting roofing felt shirt from unwinding. Wide packing tape will help us here. We will fasten it in 4 places (more is possible, the main thing is to secure it). If you have roofing felt with a dusty coating, then the tape will not stick to it. There is an option to wrap the roofing felt sleeve first with stretch film and then with tape. This will also give more rigidity to your formwork.

2. Attach a garbage bag to the bottom of the roofing felt formwork. What is it for. If you have high groundwater or simply standing water from rain, then pouring concrete into water is not recommended. The package will also act as a kind of barrier between the soil environment and concrete. According to TISE technology, the package is not used. Cement laitance enters directly into the ground forming soil concrete, which is an additional reinforcement for support (according to Yakovlev, the author of the TISE technology).

Do not confuse a garbage bag for a garbage can with a 120 liter garbage bag, which is used to collect garbage during cleanup days. It is large and quite dense. This is what we will use. We attach it to the bottom of our formwork with tape. Our roofing felt formwork is movable, so try to use tape so that it really firmly fixes the package (tightly wrap the edge of the package to the roofing felt shirt with tape). © www.site

3. The part of the package that will be used for widening can be carefully hidden in the formwork pipe.
Important! Consider the placement of the package so that when filling the concrete, folds do not form, which could make our widening not a solid structure.

We create reinforcement cages for our piles

For this task we will use reinforcement with a diameter of 10 mm. The reinforcement frame can be manufactured in 2 versions: with reinforcement for the pillar widening and without reinforcement for the widening. How much reinforcement is needed to widen a pillar is a controversial issue and can only be resolved as a result of accurate design calculations, taking into account all technical characteristics materials, loads and taking into account all possible factors. Therefore, in this article we will take the difficult path and consider a more reliable option for reinforcing the heel of the pillar.

Work plan. We prepare 4 rods about 2.4 m long (1.65 m in the ground + 0.3 m above the ground + 0.3 for connection with the grillage + 0.1 m for the heel of the pillar). To reinforce the widening of the pillar, we will bend the ends of the reinforcement so that it looks like the letter L. The length of the bend will depend on the diameter of the heel in the place where its reinforcement will take place (3-5 cm from the bottom of the widening). In our case, the length of the bend is somewhere around 10-13cm. After we have the rods ready, we sew them into a reinforcement frame. Welding, of course, is not suitable here, so we will tie it together using binding wire. At the same time, we make the connection not very strong, so that it is possible to rotate the reinforcement along its axis. It is advisable to make notches at the ends of the top of the reinforcement so that there is a guideline for how much to twist the reinforcement so that it is placed in our widening at the desired angle.

If you decide to make a reinforcement frame without widening reinforcement, then in this case we do everything the same as above, only we make the connection of the reinforcement rigid (by welding or knitting wire).

Work plan for the formation of a pillar with widening

1. We lower our formwork into the well until the end.

2. We will fill the pillar with concrete in two steps.
First, we pour a mixture of concrete to create the heel of the bored pile. It is not worth pouring a lot at once, since it will be difficult to lift the formwork and the load on the package will be too great. Adjust the fill to your liking.
To calculate the composition of concrete, we suggest using our service: Calculator for calculating the composition of concrete.

3. Raise our roofing felt glass up to the height of the widening. As a result, the poured concrete fills the package and forms the heel of our pillar. Then we press the formwork down a little.

4. We insert the reinforcement cage into the formwork and push it into the concrete solution to the depth we need.

5. We unfold the reinforcement bars along the axis to reinforce the heel of the post. How to do this and how the heel reinforcement will look, see the pictures below.

6. We bring the pillars to one level. When the concrete has set a little and the formwork has already been fixed, we mark the general level of all bored piles using a laser level or hydraulic level. As a mark on roofing felt formwork, you can use a self-tapping screw or a nail inserted into the formwork at the marked level. It is up to this mark that we will pour concrete into our piles.

7. We pour concrete to the level marks with the obligatory compaction of the solution using vibration or bayonet. For bayoneting, you can use conventional reinforcement D10-D12. In order not to damage the above-ground part of the formwork during concrete pouring, you can build a kind of removable rigid frame. A piece is suitable for this role metal pipe, close to our formwork in diameter. You can simply build formwork from boards, which we will transfer from one pillar to another during pouring.

After pouring, the concrete must mature. To prevent it from drying out in the first days, you can pour wet sawdust on the top of the post and cover it with a bag.

8. We cut our formwork to the marked level.

Conclusion

As we can see, creating a columnar foundation with your own hands is feasible even for one person. This is one of its main advantages, for those who like to do everything with their own hands without hiring hired force and special equipment. Well, we must not forget that there is a significant saving in materials, unlike strip foundation and especially a monolithic slab.