How to fill bored piles. Bored piles

For a strong and functional foundation, bored piles are often used. This is a type of pile foundations, when concrete is poured into a well made in the ground, in which a reinforcing frame is placed. On loose soils, special formwork or a casing pipe are used for strengthening. This technology is suitable for building country houses, industrial facilities. It is used for work in urban areas, where vibration is contraindicated for surrounding buildings.

Description and application

The technology of a bored foundation made of piles with a binding grillage is described in the building rules SP 50-102-2003. Several basic methods for arranging bored foundations:

Use of a continuous auger (CSA) with simultaneous supply of concrete mixture from bottom to top of the well through a process valve.
Protection against destruction of the walls of the hole in the ground by creating a counterpressure of the bentonite mortar.
The use of casing pipes immersed and retrieved by vibratory hammers or "dreiteller" (rotary plunger).

According to each of the technologies, concrete is fed into the well, with reinforcement pre-installed in it, and seizes directly in the ground. On loose, mobile, wet soils, in private construction, casing pipes are required to hold the concrete in the well. After the concrete mixture has hardened, the pipes are carefully removed or left as fixed formwork.

Bored piles are used when it is difficult to use other types of pile foundations:

in a city where the noise during driving can have a negative impact on the surrounding residents;
on swampy, weak soils, the code is required to get to the hard layers;
when erecting structures on sites with a steep slope;
in industrial construction.

The bored foundation must be made with a grillage, which is a frame made of reinforced concrete monolith connecting the pile heads. This is done to evenly distribute pressure on each element of the base. It turns out a solid strip foundation with bored piles, which can be used on difficult soils.

Classification

The bored foundation is classified depending on the manufacturing technology. On clay and other dense soils, the CPS technique (continuous hollow auger) is used. The auger is a hollow pipe closed with a check valve that prevents the excavated soil from entering it. A strong spiral is attached to the pipe, lifting the soil to the surface like a classic drill. When the desired depth is reached, it is fed into the pipe cavity under high pressure concrete. It opens the valve, gradually filling the well as the auger rises up. To make the bored pile stronger, a reinforcing frame is introduced into the concrete with a powerful vibrator. After pouring, the pile is left until the solution gains the desired strength.

The second technique is the installation of bored piles with a casing, this technology is used on unsteady soils. The pipe protects wells from collapse when a reinforcing structure is introduced into it or excessive pressure is applied to the poured solution. To do this, a well is drilled along the diameter of the pipe, which is placed into it by rotation, indentation, or simply installed there. After that, the drill is removed from the ground, reinforcement is installed in the well so that a protective layer of concrete of about 60 mm is formed. Then the solution is poured with simultaneous compaction, and the casing is gradually removed from the well.

Technology features

In the construction of a bored foundation is becoming increasingly popular. This is due to the advantages of this technology, which makes it possible to erect structures on almost any soil. The features of bored piles include:

A wide range of applications, the ability to use both on dense and unsteady soils (heaving or loose soils, near water bodies).
Quick foundation. Technology using bored piles allows you to do all the work faster than pouring a strip base or a Swedish slab.
Built in compliance with all standards, the foundation on bored piles will last at least 150 years.
Simplicity of design due to the relatively small amount of earthworks, it is enough to drill wells.
Possibility self-selection diameter and height of supports, type of reinforcement, depending on the properties of the soil and design features building.
Increased bearing capacity. Such a foundation can withstand the weight of multi-storey, industrial buildings, massive reinforced concrete structures.

The pile diameter is selected in accordance with the current SNiP after geodetic surveys, taking into account climatic and geological features. Directly during the design, the mass of the building, the number of supports are calculated and the type of soil is determined. Information on the bearing capacity of bored piles on different soils can be found in the table:

The technology of the bored foundation has disadvantages, which include:

the use of heavy equipment for drilling, installation of casing pipes, reinforcement at large construction sites;
relative complexity of technological processes;
the need for calculations.

The device of the bored foundation

This type of foundation is used not only in industrial, but also in private construction. Building a foundation on bored piles requires special equipment, but it is faster and cheaper than pouring a popular strip foundation. Important feature bored foundation - the possibility of its independent device using hand or power drills.

Before starting work, it is necessary to prepare tools and materials:

a tape measure, a coil of cord, a set of pegs and a marking hammer;
drill for wells - manual, with an electric drive or on an internal combustion engine;
formwork made of roofing felt, plastic, reinforced concrete or asbestos cement so that they can be left in the well; for industrial construction, removable casing pipes will be needed;
fittings for supports and grillage;
tool for preparing concrete mortar, cement, crushed stone, sand.

Necessary calculations

In order to correctly calculate the number of bored piles, it is necessary to determine the total mass of the building (the weight of the walls, floor slabs, communications, furniture, etc.). Given that the piles are made of M300 concrete, with standard reinforcement, the bearing capacity of one bored pile can be found from the table:

Pile diameter, mm	Support area, cm²	Bearing capacity, kg	Volume of concrete, m³	Number of vertical reinforcement bars, pcs	Consumption of fittings, rm. m
150	177	1062	0,0354	3	7
200	314	1884	0,0628	4	9
250	491	2946	0,0982	4	10
300	707	4242	0,1414	6	14
400	1256	7536	0,2512	8	18

With the help of portable drills, wells with a diameter of up to 200 mm can be prepared, so they are most often used in private construction.

To calculate the depth of the support, you need to find out the depth of soil freezing in the area and add 20 centimeters. For example, if freezing reaches 1.3 m, then bored piles are immersed to a depth of 1.5 m. On heaving, loose, marshy and moving soils, additional studies will be required, and when deepened, it will be necessary to get to layers with hard rock.

To calculate the number of piles, it will be necessary to divide the mass of the building by the bearing capacity of one support, and multiply the result by an error factor of 1.2. It takes into account possible inaccuracies in determining the mass of the grillage, furniture, snow load.

Preparation and marking

The layout of the foundation begins with a scheme of the pile field, which indicates the arrangement of bored supports. To do this, at the corners of the site, to make sure that it is rectangular, you need to measure the diagonals, they must be equal.

The first four bored piles are installed at the corners, the rest should be evenly distributed under the bearing walls. In places where wells will be made, pegs are hammered.

The distance between bored piles with a grillage according to technology should not exceed 2 m, but not less than 3 pile diameters, so as not to disturb the soil structure.

Mounting

After preparatory stages you can start installing bored piles with your own hands. With a manual, mechanical or electric drill, we make wells to a given depth, according to the markup.

Prefabricated reinforcing cages are lowered into the wells, casing pipes are installed. They can be made of metal, plastic, roofing material, asbestos, reinforced concrete. In private construction, they serve as a fixed formwork for future bored piles. The main condition is the exact vertical installation in terms of level.

The space between the casing pipes and the well is filled with soil, which is periodically compacted. In this case, it is required to control the verticality of the pipe. The height of the piles is checked with a hydraulic or laser level so that the piping is horizontal. If the pipes are higher, they are cut off, the reinforcing cage remains as the basis for tying the grillage.

M300 concrete mortar is poured into the prepared formwork, which is compacted with a manual rammer or vibrator. The poured bored piles are left until the cement has completely set for 2-3 weeks.

Filling the grillage

To achieve maximum strength, the bored foundation is connected with a grillage - a reinforced concrete tape or frame. It evenly distributes pressure on all piles. The grillage device is similar to the construction technology of a standard strip foundation. The only difference is that its lower part is on weight, not resting and not going deep into the ground. The basis of the grillage are pile heads raised above the ground to the design height.

The width of the grillage is equal to the thickness of the bearing walls, the height - for wooden, foam concrete walls is equal to the width. For stone and brick buildings - 50% more width. The grillage is poured in several stages:

formwork is mounted in the form of a box, in which holes are made for piles and future utilities;
monolithic grillage must be reinforced according to the requirements for reinforced concrete structures, the frame is connected with the protruding reinforcement of the bored supports;
concrete mixture is poured into the formwork, which must completely set, then the formwork is dismantled;
the surface is waterproofed with a tape of roofing material, folded in two layers, or with coating compositions.

Despite the fact that the bored foundation can be made independently, during the construction there are many points known only experienced builders who share their experiences. To avoid mistakes during construction, pay attention to the following points:

carefully study the type of soil, for which it is better to perform geodetic reconnaissance, taking into account the information received when selecting the diameter and depth of installation of piles;
for private construction, do not use supports with a diameter of more than 200 mm, since their installation will require special equipment, which will make the foundation more expensive;
when pouring casing pipes, part of the reinforcement should protrude to the height of the future grillage to give it additional strength;
pouring the grillage can only be done after the solution has completely set in bored piles;
the distance between the lower part of the grillage and the ground surface should not be less than 150 mm so that it does not deform during swelling.

The construction of foundations from bored piles is a technology that is gaining popularity. It allows you to create a solid and inexpensive foundation for both private houses, light structures, and industrial buildings on any soil. The cost of constructing such a foundation is lower than for the construction of a classic strip foundation, buried below the level of soil freezing, by an average of 40%. At the same time, indicators of strength and durability remain comparable.

A bored foundation is one of the foundation options that is perfect for difficult terrain with sharp elevation changes and difficult soil, in the presence of dense buildings in the settlement, in places with a risk of damage to neighboring buildings and communications.

When it is not possible to install a traditional one, it can easily be replaced by a bored foundation, which has correct installation sufficient bearing properties.
In addition to those already listed above, an important advantage of the bored foundation is that the technology of its construction allows you to work at any time of the year, low noise production, ease of installation.
The very technology of erecting a bored foundation saves you from the need to purchase and deliver piles and other structural elements to the construction site.

Design features for a house with a grillage

The construction of this type of foundation, as a bored foundation, is the drilling of post holes in the soil, into which it is immersed metal carcass, and notice all this is poured with a concrete mixture or a solution of cement with sand.

The bored foundation is mounted directly on the building site. When starting, it is necessary to take into account the nature of the soil (the level of its freezing) and the weight of the future structure. As a rule, the width of the future foundation should be 30-40 cm more than the expected width of the external and load-bearing walls of the house.

Stages of installation of a bored foundation

Stage 1. Calculation of the foundation for piles

The first step is to calculate the building site. Don't worry for frame house, do not need a powerful zero level. AT frame houses light, but if you are building a massive house, then the piles will have to be made 30-40 mm thicker so that the load on the foundation is commensurate. The calculation table will help you.

Stage 2. We mark the site

You can choose the location of the piles in different ways, usually this is done under the main carrying houses, but you can also stagger the bored piles.

Stage 3. Drilling wells for the foundation of the house

Mark the building site, dig a trench, determine the location of the pillars and align the line with a fishing line and level.

We provide drilling and insulation. Then, with the help of a motor drill or a special drilling machine, wells of a given diameter are drilled in the marked places.

Stage 4. Production of wooden formwork

Formwork is necessary where there is the possibility of shedding, for piles, formwork wrapped in a tube can play a role. For strip foundations, we produce wooden formwork.

Stage 5. Pile strength

In order for the piles to serve for a long time, choose piles of better quality, bored piles can be placed at a distance of a couple of meters from each other, depending on your home. If your piles are 50 cm in diameter, each pile can withstand up to 5 tons, which gives you the opportunity to build even from high reliability.

Stage 6. sand cushion

At the bottom of the well, a pillow of sand or gravel is arranged, which is manually compacted. After that, the prepared construction quick-hardening cement mixture (concrete) is poured into the pit, sometimes it is combined with stones. A prerequisite is the filing concrete composition at a certain level of vibration and in small portions. This will eliminate the formation of air voids and provide the foundation with strength and durability.

Stage 7. Rebar knitting

It is better to use fittings with a diameter of 10-12 mm. They will provide sufficient structural strength.

At the next stage, we knit a reinforcing cage, the lower edge of which should remain immersed in concrete mix and do not touch the bottom of the pit. Otherwise, the metal will be susceptible to corrosion, and the bored foundation will lose its strength.

Stage 8. We waterproof wells

To ensure the strength of the future bored foundation, wells are drilled using a layer or two of roofing material. On soils with high humidity casing pipes are used for protection.

Stage 9. Pouring the foundation with concrete

The reinforcement is installed in the formwork in the form of a grid, however, not in contact with it. For this, the reinforcing cage is connected to the pile frame. Then the formwork is poured with mortar, after it hardens, the bored foundation is considered ready.

At the final stage, installation takes place, which combines the parts of the bored foundation protruding above the ground. The most durable is considered monolithic of reinforced concrete. To install it, you will need reinforced concrete mortar, reinforcement and wooden structures under formwork. After that, you need to let the foundation dry for up to one month.

Bored piles are a type of pile foundation, which involves the construction of piles by drilling holes in the ground, followed by their reinforcement and concreting. The result is a solid monolithic base, capable of absorbing heavy loads not only from the erected building, but also from side 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, device technology. For private construction, two types of bored supports are used:

Cylindrical. They have the same diameter throughout the body of the support.
With a broadened supporting sole - the fifth. The device of piles with a fifth - difficult process, which is impossible without special equipment - drill strings with cutters. In dense soils, an explosive method is used to develop a widening.

When building cottages with your own hands without hiring a contractor, supports with a wide heel are not used. Primitive widening can be arranged if casing is used, but it has nothing to do with the calculated heel that is performed during construction multi-storey buildings in accordance with SNiP.

The foundation on bored piles is used in multi-storey and private construction in the following cases:

In dense building 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 building houses using heavy building materials (granite, ceramic bricks).
If there is a threat of flooding of the site, near water bodies, with a high occurrence of groundwater.
In the absence of data on hydrogeological surveys on the site.

Pros and cons of a bored foundation

The foundation of the bored type has both advantages and disadvantages inherent in all pile foundations. Among benefits note:

versatility, suitable for soils with any characteristics;
high bearing capacity;
simple calculations and diagrams, you can not order a project;
service life of at least 100 years;
installation can be done by hand, without resorting to the help of contractors;
no need to dig a pit;
minimum loads on the soil of neighboring areas;
the possibility of preserving the improvement of the territory;
low cost in comparison with other types of foundations.

To shortcomings structures can include:

relatively large amount of concrete work;
the need to strengthen wells in loose soils;
time-consuming installation process;
the impossibility of building a basement in the house.

Bored or screw piles: which is better?

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

Evaluation criterion	Bored piles	Screw piles
Bearing capacity of a pile with a diameter of 50 cm	Withstand 4 tons	Withstand 1.5 tons
Resistance to corrosion and aggressive environments	High	Low
Assortment and dimensions	Not limited	Limited by existing sizes
Use in soils	In all soils except rocky	Not used in rocky, swampy, alkalized soils
Installation labor intensity	Medium: requires drilling, reinforcement, concreting	Low: piles are screwed into the ground
Installation time	Depends on concrete work	In any season
Life time	At least 100 years old	25 to 50 years old

The cost of screw piles depends on the size of the metal used for their production 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 device requires much more effort than the installation of screw piles.

Calculation and layout of bored piles

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

Studying the characteristics of the soil on the site. If hydrogeological surveys have been carried out, then data on them can be found in the project. In the absence of information about the surveys, it is necessary to carry out pitting. A pit is a vertical exploratory excavation of soil 1.5-3 m high, which serves to study the layers and their characteristics. The purpose of pitting is to determine the depth of bearing soils. Drilling can be done independently using a regular garden drill.

Expert opinion

Sergei Fedorov

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Conduct exploration drilling necessary not only before the detection of bearing soils, but also to determine their thickness.

The characteristics of the soils, which are determined during the 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 the loads, a project and an estimate for materials are required. It is best to calculate loads using special programs, for example, Foundation, Base 6.2, etc. When building a small, light building, you can use a calculator like "Weight-House-Online v.1.0". Also, load calculations can 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 proceed to its calculation according to the following algorithm:

Calculation of the bearing capacity. To simplify the task and not to make complex calculations, we suggest using the table, which indicates the bearing capacity of bored supports different diameter depending on the type of soil:

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

Selection of section (diameter). When choosing the optimal diameter, it must be taken into account that large-section piles will require not only a lot of concrete mix, 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 heavy ones - 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 the 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 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 should be remembered that the higher the mass of the structure, the less step piles. The minimum distance can be 50 cm.

Depth of occurrence or length of piles. It is determined based on the depth at which the bearing soils are located. The depth of pile driving should be below the freezing level, even if the bearing layers are located higher. Information about the depth of freezing for your area can be found on the Web.

Calculation example: The construction of a cottage takes place in the Moscow region on sands of medium density. The size of the house is 10 x 10 m, the total load is 60 tons. For the foundation, we select piles with a cross section of 30 cm. Based on the table, we find that the 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 base layers, is 2.2 m.

To draw up a layout of pile supports, it must be taken into account that piles must be located at each corner of the house, along load-bearing walls with a selected pitch, as well as under the entrance group and heavy structures.

Do-it-yourself bored foundation device

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 mounting methods:

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

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

Expert opinion

Sergei Fedorov

Professional builder. Experience 18 years

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

The installation of pile supports can be started after marking the future foundation. Marking is carried out using poles and twine. For a future tape or monolithic base of a shallow type, a trench or a 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:

Well drilling and casing installation

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

prevention of shedding of the well wall;
waterproofing of concrete piles;
simplified installation of the armoframe;
easier concrete pouring.

The use of casing pipes also has disadvantages:

increase in the scope of work;
foundation cost.

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 more than the calculated length of the piles. Installation of pipes is mandatory 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 indentation or driving with a sledgehammer. The pipe must be installed inside the well strictly vertically. Position controlled building level. Tolerance for a pipe of 2 m is no more than 1 cm to the side. The gap between the wall of the well 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. Reinforcement for bored piles is connected into a spatial reinforcement cage. The number of longitudinal reinforcement bars is 4 or 6. Vertical bars are installed every 30-40 cm. The diameter of the used reinforcing bars of class A3 is 15-20 mm. The length of the rods should be 0.5 m longer than the length of the casing. The reinforcement used for the reinforcement cage must comply with GOST 5781.

Knitting of reinforcing 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 armogib or a knitting gun as follows:

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

Expert opinion

Sergei Fedorov

Professional builder. Experience 18 years

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For reinforcement of bored piles, reinforcing waste, as well as rusty and dirty reinforcement, must not be used.

The finished reinforcing 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

Concrete of class B22.5 is used for concreting. For light buildings, it is allowed to use a concrete mixture of class B15 ... 17.5. 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-manufacturing concrete mixture must be strictly adhered to the recipe.

The best option is to order ready-made concrete with delivery. In this case, it is advisable to order ABS with a hose of the required length, through which the mixture will be supplied to the wells. Also note that it takes 10-20 minutes to concrete each pile, and the ABS free parking time is 1 hour. For the time that the mixer will spend on your site in excess of this rate, 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 vibrate ramming. Then the next portion is poured and compacted. The pile head is formed by pouring the casing up to the top edge. Concrete hardens within 7-10 days.

The device of the heel - the base of the bored support.

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

soil bursting at the wellhead with a reinforced rammer, followed by pouring the concrete mixture;
use of a casing pipe with broadening from below.

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 a large mass, it is not advisable to widen it.

Cutting casing pipes and fittings

Pruning is done by a grinder. Reinforcing bars should protrude from the pile head, but be equal in height. With the help of the protruding reinforcement, the pile foundation will be connected to the ground part.

The device of the ground part of the foundation

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

Pile-monolithic. A combined type of foundation, in which a monolithic slab is poured over the pile field. It is used mainly on dense soils and for buildings with a large mass. Advantages: the highest 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 tape, poured with 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, a hanging strip base is required, which is almost impossible to independently calculate and perform.
Pile-grillage. By design, it resembles a pile-tape base, but instead of a monolithic tape, the load from the structure is perceived by the grillage. Foundation with grillage is great for small country houses, baths, outbuildings. Pros: easy installation, possibility self-arrangement metal hanging grillage. Disadvantages: relatively low bearing capacity.

When choosing a ground part for a bored foundation, it is necessary to take into account the characteristics of the future house (mass, area), soil types on the site and financial capabilities. When calculating the cost of a combined foundation, do not forget to include in the estimate the work and materials for insulation, waterproofing, and finishing.

Bored piles are vertical pillars that are poured directly on the construction site. To install them, a well is drilled in the soil, which is then poured with concrete. They have already received wide use and actively displace foundation supports.

Applications

The presented equipment is used in the following cases:

for the construction of tall and bulky industrial and office buildings;
during the construction of facilities on swampy terrain or other weakened soils;
for the construction of houses on difficult terrain;
when hard rocks that can withstand the load of the building lie quite deep.

Bored piles, unlike driven and screw piles, have more reliable design and do not corrode. The requirements for foundations are described in the Code of Rules SP 24.13330.2011, in accordance with which the work must be carried out.

Kinds

By design, the equipment is of the following types:

Cylindrical. Made in the form of a cylinder, inside which there is a longitudinal section, the same along the entire length of the structure.
With base sole. The lower part of such piles has a large diameter.

Divided by size:

short;
long.

According to the material of manufacture:

wooden;
concrete, reinforced concrete;
soil-concrete;
combined.

Installation technology:

According to the manufacturing method:

According to the method of construction, piles are divided into the following types:

The following methods are now widely used to install piles:

Piles with casing

The equipment is presented in the form of a metal or plastic cylindrical structure, which is installed inside the well. The pipe is designed to prevent shedding of soil from its walls. Used on watery and unstable soils.

There are several options for immersing the pipe in the soil:

In production, two methods of installation of the presented equipment are used:

The first way is to install bored piles in dry soil. Initially, workers using a drilling rig dig a well of a certain depth and section. Further, an expander is lowered to its bottom and a camouflage heel is made. Then it is necessary to remove the soil and install the reinforcing cage. Next, you need to lower the concrete casing pipe there, concrete the inner surface of the pipes and process the heads of the pile supports with a special conductor. When installing bored piles with a casing using this technology, their diameter can vary from 500 to 1200 mm.
Installation of piles on soil with a high content of groundwater. To install a pile, it is necessary to dig a well, make a heel, insert a reinforcing cage and install a casing pipe. A clay solution is poured into the resulting well through the drilling rig, which is absorbed, forming a crust on the walls. It prevents the collapse of the soil. Next, a frame and a pipe are placed in the well. When the concrete supply process begins, it is slowly pulled out.

The choice of pile installation method directly depends on the characteristics of the soil. Basically, casing pipes do not remain inside wells, but according to regulatory documents, people have the right to leave them in case of landslides on slopes or when groundwater moves at a rate of more than 200 m per day.

Piles with grillage

Grillage - the upper part of a pile or column foundation, the main task of which is to distribute the load from the load-bearing structural elements. Basically it is a reinforced concrete frame, which is located under bearing walls buildings.

The frame happens:

low - completely goes into the soil, its top is at ground level or below;
elevated - the lower part of the frame is at ground level;
high - the frame is located above the ground.

To install the grillage, the frame rods that emerge from the concrete remain in the pile heads. Reinforcing bars are screwed to them and a two-tier frame is made. Next, formwork is made and installed. This is an auxiliary wooden, metal or plastic structure that gives shape to concrete products. The width of the frame should be equal to the thickness of the wall of the building. Then the formwork is poured with concrete and compacted.

The foundations from the presented equipment have a number of the following advantages:

It is possible to install piles without casing pipes only on stable soils. Piles with casing pipes can be erected on any type of soil.

The use of bored piles allows you to reduce the cost of building materials, reduce the time of foundation construction. They are able to withstand heavier structures, so choosing this type of foundation will increase the area of \u200b\u200bthe building being built by increasing the number of floors. The construction process will not seem so difficult, and the house will be commissioned ahead of schedule, which will undoubtedly bring a good profit to the developer.

Advantages

Economical. Requires less materials, namely concrete and reinforcement, in comparison with the strip and slab foundation.
Does not require the manufacture of removable formwork. A fixed formwork is used, the manufacture of which takes a small amount of time.
The foundation of bored piles can easily be made independently without the involvement of special equipment and hired labor.

disadvantages

Unlike tape, there is no way to make a cellar and a basement.
A more detailed design is required, in contrast to the tape and slab.

The average service life of a columnar foundation made of bored piles is 150 years.

Designing a columnar foundation from bored piles

The total weight of the future house is calculated.
We do an examination of the soil (test drilling). We find out the bearing capacity of the soil, the groundwater level (GWL) and the depth of soil freezing (GPG).
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 bear the full load of the house. The bearing capacity of the soil is taken into account in the calculation. In order to increase the area of the surface supported on the ground, a broadening is used at the bottom of the column (the average value of the heel diameter is 400-600 mm).
The distance between the posts should be within 1-3m (average value 1.5-2m).

Drilling of the wells

We drill wells for piles. AT this example we will make the diameter of the pits 25 cm to a depth below the freezing depth for a given area. Suppose we have a freezing depth of 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.

More important point. All wells can be drilled 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. Water will wash away the soil of the walls of the well, as a result of which it will crumble, and we do not need this at all.

We make widenings at the bottom of the wells

What is it for. By widening in the well, a heel of the column will be formed, which will perform 2 tasks: increasing the bearing capacity of the column 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 broadening with a diameter of 40-60 cm. But it is worth noting that it is very difficult to work with this device in dense soil. Therefore, it is advisable to check everything during test drilling during the design of a columnar foundation.

There is an alternative and budgetary way to widen using a modernized bayonet shovel. To do this, it is necessary to cut 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 raise the soil from such a widening, you can use some kind of device, or simply drill deeper and rake all the soil from our widening into this recess. The main thing is not to forget to tamp our "burial" afterwards.

Creation of fixed formwork from roofing material

1. As a formwork for a bored foundation, in this example we will use the most economical option, namely ruberoid.

We prepare a piece of roofing material of the length we need. In our example, we need a piece 2m long (1.7m underground - 0.3m widening without tar paper + 0.3m above ground + 0.3m margin for trimming by level). We twist the roofing material of the diameter we need (25 cm) in the form of a pipe. For this task, it is better to use a certain template on which we will wind the roofing material. For example, we have a metal pipe. The template can be made independently, being smart. There are many options.

After the roofing material has been wound up (thickness is 2 layers), it is necessary to fix the resulting shirt from roofing material from unwinding. Here we will be helped by a wide packing tape. Fasten in 4 places (more is possible, the main thing is to be reliable). If you have a roofing material with powdered dressing, then the adhesive tape will not stick to it. There is an option to wrap the roofing material sleeve first with stretch film and then with tape. This will also give more rigidity to your formwork.

2. We fasten the garbage bag to the bottom of the roofing material formwork. What is it for. If you have high ground water or just standing water from the rain, then pouring concrete into the water is not recommended. Also, the package will be a kind of barrier between the soil environment and concrete. According to TISE technology, the package is not used. Cement milk enters directly into the soil, forming soil concrete, which is an additional reinforcement for the support (according to Yakovlev, the author of the TISE technology).

Do not confuse a garbage bag for a garbage can with a garbage bag 120l, in which garbage is collected on subbotniks. It is large and quite thick. Here we will use it. We fix it to the bottom of our formwork with tape. Our roofing material formwork is movable, so try to use adhesive tape so that it really fixes the package tightly (strongly wrap the edge of the package to the roofing material shirt with adhesive tape). © www.site

3. The part of the package that we will use for widening can be carefully hidden in the formwork pipe.
Important! Consider the placement of the package so that during the filling of the concrete there are no wrinkles that can make our extension not a solid structure.

We create reinforcing cages for our piles

For this task, we will use reinforcement with a diameter of 10mm. Reinforcing cage can be made in 2 versions: with reinforcement of the column broadening and without reinforcement of the broadening. How much reinforcement is needed to widen the column is a moot point and can only be resolved as a result of accurate design calculations, taking into account all specifications materials, loads and taking into account all possible factors. Therefore, in this article we will take a difficult path and consider a more reliable option for reinforcing the heel of the column.

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 broadening of the column, 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 it will be reinforced (3-5 cm from the bottom of the widening). In our case, the length of the bend is somewhere around 10-13cm. After the bars are ready, we sew them into a reinforcing cage. Welding here, of course, is not suitable, so we will tie it with a knitting wire. At the same time, we make the connection not very strong, so that it is possible to scroll 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 fits in our widening at the right angle.

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

Work plan for the formation of a column with broadening

1. We lower our formwork into the well to 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 raise the formwork and there will be too much load on the package. 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. We raise our glass of roofing felt up to the height of the broadening. As a result, the poured concrete fills the package and forms the heel of our post. 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. Expand the reinforcement bars along the axis to reinforce the heel of the column. How to do this and how the heel reinforcement will look, look at the pictures below.

6. We display the pillars in one level. When the concrete sets a little and the formwork is already fixed, we mark the general level of all bored piles using a laser level or a hydraulic level. In the form of a mark on the roofing felt formwork, you can use a self-tapping screw or a nail stuck 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 by vibrating or bayoneting. For bayoneting, you can use conventional fittings D10-D12. In order not to damage the above-ground part of the formwork during concrete pouring, it is possible to build some kind of removable rigid frame. For this role, a piece metal pipe close to our formwork diameter. You can simply build a formwork from boards, which we will transfer from one pillar to another during pouring.

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

8. We cut our formwork at the marked level.

Conclusion

As you can see, the creation of 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 the involvement of hired forces and special equipment. Well, we must not forget that there is a significant savings in materials, in contrast to the strip foundation, and even more so a monolithic slab.

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