On conventional piles, bored technology. How to make your own foundation on bored piles. Work plan for the formation of a pillar with widening

Bored piles are often used for a strong and functional foundation. This is a type of pile foundation, when concrete is poured into a hole made in the ground, in which a reinforcing frame is placed. On loose soils, special formwork or casing are used for strengthening. This technology is suitable for the construction of country houses and 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 connecting grillage is described in the construction rules SP 50-102-2003. Several basic techniques for constructing bored foundations:

Using a continuous auger (CSA) with simultaneous supply of concrete mixture from the bottom to the top of the well through a process valve.
Protection against destruction of the walls of a hole in the ground by creating back pressure of bentonite solution.
The use of casing pipes loaded and retrieved using vibratory hammers or a “dreiteller” (rotating loader).

According to each of the technologies, concrete is fed into the well, with reinforcement pre-installed in it, and set directly in the soil. On loose, moving, 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 permanent formwork.

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

in the city, where noise from driving can have a negative impact on surrounding residents;
on swampy, soft soils, when it is necessary to get to hard layers;
when constructing structures on sites with a steep slope;
in industrial construction.

A 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. The result is a strong strip foundation with bored piles, which can be used on difficult soils.

Classification

The bored foundation is classified depending on the manufacturing technology. On clayey and other dense soils, the NPSH (continuous hollow auger) technique 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 required depth is reached, concrete is fed into the pipe cavity under high pressure. It opens the valve, gradually filling the well as the auger rises upward. To make the bored pile stronger, a reinforcing frame is introduced into the concrete using a powerful vibrator. After pouring, the pile is left until the solution reaches the required strength.

The second technique is the installation of bored piles with a casing; this technology is used on unstable soils. The pipe protects wells from collapse when a reinforcing structure is introduced into it or excess 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, pressing, or simply installed there. After this, the drill is removed from the ground, and 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.

Features of the technology

In construction, bored foundations are becoming increasingly popular. This is explained by the advantages of this technology, which allows the construction of structures on almost any soil. Features of bored piles include:

Wide range of application, possibility of use on both dense and unstable soils (heaving or loose soils, near water bodies).
Fast construction of the foundation. Technology using bored piles allows you to complete all work faster than pouring a strip base or 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 volume of excavation work; it is enough to drill wells.
The ability to independently select the diameter and height of the supports, the type of reinforcement, depending on the properties of the soil and the design features of the building.
Increased load-bearing capacity. Such a foundation can support the weight of multi-story, industrial buildings, and massive reinforced concrete structures.

The diameter of the pile is selected in accordance with the current SNiP after geodetic surveys, taking into account climatic and geological features. Directly during 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:

Bored foundation technology has disadvantages, which include:

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

Construction of a 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 the popular strip foundation. An important feature of a bored foundation is the possibility of its independent construction using hand-held or motorized drills.

Before starting work, you need to prepare the tools and materials:

tape measure, a roll of cord, a set of pegs and a hammer for marking;
drill for wells - manual, electrically driven or with 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;
reinforcement for supports and grillage;
tools 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 (weight of walls, floor slabs, communications, furniture, etc.). Considering that the piles are made of M300 concrete, with standard reinforcement, the load-bearing capacity of one bored pile can be found in the table:

Pile diameter, mm	Support area, cm²	Load capacity, kg	Volume of concrete, m³	Number of vertical bars of reinforcement, pcs.	Reinforcement consumption, linear 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

Using portable drills, you can prepare wells with a diameter of up to 200 mm, which is why 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, swampy and mobile soils, additional research will be required, and when deepening it will be necessary to get to layers with hard rock.

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

Preparation and marking

The foundation layout begins with a diagram of the pile field, which indicates the placement 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 in the corners, the rest should be evenly distributed under the load-bearing walls. In the places where the wells will be made, pegs are driven in.

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

Installation

After the preparatory stages, you can begin installing bored piles with your own hands. Using a manual, mechanical or electric drill, we drill holes to a given depth, according to the markings.

Prefabricated reinforcement cages are lowered into the wells and casing pipes are installed. They can be made of metal, plastic, roofing felt, asbestos, reinforced concrete. In private construction, they serve as permanent formwork for future bored piles. The main condition is precise vertical installation in level.

The space between the casing pipes and the well is filled with soil, which is periodically compacted. In this case, it is necessary 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 reinforcement cage remains as the basis for tying the grillage together.

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

Pouring the grillage

To achieve maximum strength, the bored foundation is connected with a grillage - a reinforced concrete strip or frame. It distributes pressure evenly on all piles. The construction of the grillage is similar to the construction technology of a standard strip foundation. The only difference is that its lower part is suspended, without resting or going deep into the ground. The basis of the grillage is the pile heads raised above the ground to the design height.

The width of the grillage is equal to the thickness of the load-bearing walls, the height for wooden and 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 installed in the form of a box, in which holes are made for piles and future utilities;
a monolithic grillage must be reinforced according to the requirements for reinforced concrete structures, the frame is connected to the protruding reinforcement of bored supports;
a concrete mixture is poured into the formwork, which must set completely, then the formwork is dismantled;
The surface is waterproofed with a roofing felt tape folded in two layers, or with coating compounds.

Despite the fact that you can make a bored foundation yourself, during construction there are many aspects known only to experienced builders who share their experience. 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;
the grillage can be poured only after the mortar in the bored piles has completely set;
the distance between the bottom 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 durable and inexpensive foundation for both private houses, light structures, and industrial buildings on any soil. The costs of constructing such a foundation are lower than those of constructing a classic strip foundation, buried below the freezing level of the soil, by an average of 40%. Strength and durability indicators remain comparable.

TYPICAL TECHNOLOGICAL CARD (TTK)

CONSTRUCTION OF FOUNDATIONS FROM BORED PILES IN THE CONDITIONS OF EXISTING DEVELOPMENT AND RECONSTRUCTION

1 AREA OF USE

A standard technological map has been developed for the installation of foundations from bored piles in the conditions of existing development and reconstruction.

Intended for use by construction and installation organizations in the development of design estimates and work projects.

When constructing buildings on pile foundations in cramped urban conditions, dynamic loads acting on nearby buildings pose a serious problem. A solution to this problem is possible using bored pile technology.

The scope of application of bored piles is in all soils, except rocky and coarse-clastic soils, incl. waterlogged, structurally unstable without the use of inventory casing pipes or thixotropic solutions in cramped urban conditions with an approach to existing buildings up to 1 m. In this case, when carrying out engineering-geological surveys, special attention should be paid to the inspection of foundation construction sites in order to identify various types of obstacles (rock layers, boulders larger than 25 cm, etc.).

Work can be carried out on the installation of bored piles with a diameter of 400-1200 mm and a depth of up to 25 m in various soil conditions for the construction of pile foundations near existing buildings using imported equipment from Casagranda S-40 (Italy).

Driven pile technology

Drive-in piles are installed at their future location by filling the hole (cavity) with concrete mixture or sand. Currently, a large number of solutions for such piles are used. Their main advantages:

Possibility of manufacturing any length;

absence of significant dynamic impacts during the installation of piles;

applicability in cramped conditions;

applicability when strengthening existing foundations.

Driven piles are made of concrete, reinforced concrete and soil, and it is possible to install piles with a widened heel. The method of constructing piles is simple - concrete mixture or soil, mostly sandy, is fed into pre-drilled wells for filling.

The following types of cast-in-place piles are used - A.E. Strauss piles, bored, pneumatic-rammed, vibro-rammed, frequently rammed, vibro-rammed, sand and soil concrete. The length of the piles reaches 20...30 m with a diameter of 50...150 cm. Piles produced using installations from the companies Kato, Benoto, Liebherr can have a diameter of up to 3.5 m, a depth of up to 60 m, and a load-bearing capacity of up to 500 tons.

Features of piling technology in reconstruction conditions

Specifics of piling work production. When reconstructing and technically re-equipping enterprises, there is often a need to strengthen foundations or increase their load-bearing capacity. Under these conditions, various methods of installing additional piles, the “wall in soil” method, and the modified drop-well method are used.

Installation of additional piles. With this method, bored and pressed multi-sectional piles are usually used, driven into the corners of the foundation and taking the load through a reinforced concrete cage installed along its perimeter - a grillage. However, a more effective solution is to install reinforced soil piles or cast-in-place piles directly under the base of the existing foundation using "jet-jet technology". This piling technology includes the following main processes:

drilling wells with a diameter of 100...150 mm to the soil foundation through the lower stage of the foundation at its corners, and, if necessary, between the corners;

lowering a jet monitor through a drilled hole in the foundation and subsequent drilling of a small diameter well in the ground to the designed depth by destroying the soil with a high-pressure jet from the monitor;

expansion of the well to the design section by gradually raising the monitor, through the nozzle of which an erosive jet of water or a soil-strengthening solution enters, resulting in the formation of a pile of strengthened soil.

It is possible to install a reinforcement cage into the well, extending into the existing foundation, and then fill the well with a concrete mixture if the bearing capacity of the soil piles is insufficient.

When placing soil piles under foundations using jet technology, three options are possible: one-, two- and three-component, differing in the number of components, the composition of the equipment and the load-bearing capacity of the resulting soil piles.

Single component technology provides for erosion of the soil by one or two oppositely directed jets of strengthening solution. The solution can be prepared in advance (cement-sand or cement-clay), or the required composition can be obtained by separately supplying its components to the nozzles. Mixing will occur directly at the exit from the nozzle (liquid glass and hardener, cement-sand mortar and chemical additives-hardening accelerators, etc.). With single-component jet technology, the soil is eroded within a radius of 200...350 mm from the nozzle, the diameter of the soil pile column is 0.5...0.7 m.

Two-component jet technology is carried out by simultaneous supply of a stream of strengthening solution and a concentric annular stream of air. Soil erosion by a solution-air jet occurs within a radius of 1.0...1.5 m, and the diameter of the soil pile reaches 2...3 m. three-component technology Additionally, additives are added to the soil to speed up the process of pile formation.

Using jet technology, it is possible to produce piles of various sections: screw, root-shaped, with transverse diaphragm disks, etc. Due to the developed lateral surface, the load-bearing capacity of piles is 1.5...1.8 times higher than that of piles with a round cross-section.

Screw piles are installed by lifting a monitor having one or more side nozzles located one above the other with simultaneous rotation around its vertical axis. The number of helical blades on such piles corresponds to the number of nozzles on the monitor; the pitch of the helical blades is determined by the lifting speed of the monitor.

Indentation of multi-sectional piles. Multi-section piles usually consist of three or more prefabricated short section elements. These sections are sequentially joined as they are pressed into the ground by jacks or other mechanisms to a position at which the design load-bearing capacity is ensured. The jack is installed under the base of the existing foundation, under a special beam or an inventory thrust device, anchored to fixed structures and neighboring buildings. To construct multi-sectional piles, steel pipes with a diameter of 245...400 mm with a shoe or welded lower end are used. Sections of piles about 1 m long are joined by welding as they are pressed. After indentation, the pile cavity is filled with concrete mixture. Reinforced concrete sections of piles with a section of 30x30 and a length of 60, 90 and 120 cm with a pin joint of the sections are used.

The advantages of multi-sectional piles are that the indentation is carried out in the static testing mode of the piles, there are no dynamic effects when driving piles, high reliability of reinforcement of structures is ensured and constant monitoring of the load-bearing capacity of the pile during the driving process.

Modified Sinkhole Method. This method makes it possible to increase the bearing capacity of the soil mass under the existing foundation by enclosing the soil in a reinforced concrete shell, where the soil can withstand high pressures, since it is located in a closed volume of the sink well and is subject to a triaxial stress state. The modified sump well method differs from the traditional method in that the soil is developed from the outside rather than inside the sump well. After excavating the soil to the level of the lower stage of the foundation, a well shell (prefabricated or monolithic) is arranged, it is lowered with the excavation of the soil along the outer contour, and then the walls of the shell are built up. The work is carried out sequentially until the shell is immersed at the design level.

Bored piles. A characteristic feature of the installation of bored piles is the preliminary drilling of wells to specified depths.

The very first in our country, on the basis of which existing types of bored piles are used, are the piles of A.E. Strauss, which were proposed in 1899. The production of piles includes the following operations:

drilling a well;

lowering the casing pipe into the well;

extraction of crumbled soil from a well;

filling the well with concrete in separate portions;

compacting concrete with these portions;

gradual removal of the casing.

A pipe with a diameter of 25...40 cm is carefully lowered into a well drilled to the design mark (5...12 m) and then loaded with concrete mixture. After filling the well to a depth of about 1 m, the concrete mixture is compacted and the casing pipe is slowly raised up until the height of the mixture in the pipe decreases to 0.3...0.4 m. The concrete mixture is loaded again and the process is repeated. Considering that the diameter of the well is larger than the diameter of the casing pipe and the surface of the drilled soil is uneven and rough, when filling the casing pipe with concrete mixture, lifting it and compacting the mixture, the concrete will fill the entire free volume, including the gap between the walls of the well and the casing pipe. Some of the concrete and cement laitance will penetrate into the soil, increasing its strength.

The disadvantages of this method are the inability to control the density and solidity of concrete along the entire height of the pile, and the possibility of erosion of the unset concrete mixture by groundwater.

Reinforcement of piles is carried out only in the upper part, where metal rods are installed to a depth of 1.5...2.0 m in freshly laid concrete for their subsequent connection with the grillage.

Depending on the ground conditions, bored piles are installed using one of the following methods - dry method (without fastening the walls of the wells), using a clay solution (to prevent the collapse of the walls of the well) and fastening the well with a casing pipe.

Dry method applicable in stable soils (subsidence and clay soils of solid semi-solid and refractory consistency), which can support the walls of the well (Fig. 1). A well of the required diameter is drilled using rotary drilling in the soil to a given depth. After the well has been accepted in the prescribed manner, if necessary, a reinforcement cage is installed in it and concreted using the vertically moving pipe method.

Fig.1. Technological diagram for installing bored piles using the dry method:

A- well drilling; b- drilling out a widened cavity; V G- installation of a concrete pipe with a vibrating hopper; d- concreting a well using the vertically moved pipe (VPT) method; e- lifting a concrete pipe; 1 - drilling rig; 2 - drive; 3 - auger working body, 4 - well; 5 - expander, 6 - widened cavity; 7 - reinforcement frame; 8 - jib crane; 9 - conductor-pipe; 10 - vibrating hopper; 11 - concrete pipe; 12 - tub with concrete mixture; 13 - widened pile heel

Concrete cast pipes used in construction, as a rule, consist of separate sections and have joints that allow the pipes to be quickly and reliably connected. Sections of concrete pipes with a length of 2.4...6 m are fastened at the joints with bolts or locking joints; a receiving hopper is attached to the first section, through which the concrete mixture is fed into the pipe. A concrete casting pipe is lowered into the well to the very bottom, the concrete mixture is fed into the receiving funnel from a concrete mixer truck or using a special loading hopper, vibrators are attached to the same funnel, which compact the concrete mixture being laid. As the mixture is laid, the concrete pipe is removed from the well. After concreting the well is completed, the head of the pile is formed in a special inventory jig and is additionally reliably protected in winter. The dry method using the technology discussed above produces bored piles with a diameter of 400 to 1200 mm, the length of the piles reaches 30 m.

Application of clay solution. The installation of bored piles in weak water-saturated soils requires increased labor costs, which is due to the need to secure the walls of the well to protect them from collapse (Fig. 2). In such unstable soils, a saturated clay solution is used to prevent the collapse of the well walls. bentonite clays with a density of 1.15...1.3 g/cm, which exerts hydrostatic pressure on the walls, well temporarily holds together individual soils, especially waterlogged and unstable ones, while keeping well walls of wells from collapsing. This is also facilitated by the formation of a clay cake on the walls of the well due to the penetration of the solution into the soil.

Fig.2. Technological diagram for installing bored piles under clay solution:

A- well drilling; b- device of an expanded cavity; V- installation of reinforcement cage; G- installation of a vibrating hopper with a concrete pipe; d- concreting the well using the VPT method; 1 - well, 2 - drilling rig; 3 - pump; 4 - clay mixer; 5 - pit for clay solution; 6 - expander; 7 - rod; 8 - jib crane; 9 - reinforcement frame; 10 - concrete pipe; 11 - vibrating hopper

Wells are drilled using a rotary method. The clay solution is prepared at the work site and, as drilling progresses, it is fed into the well along a hollow drill rod under pressure. As drilling proceeds, the solution under hydrostatic pressure from the drilling site, encountering soil resistance, begins to rise up along the walls of the well, carrying out the soil destroyed by the drills, and coming to the surface, enters the sump settling tank, from where it is again pumped into the well for further circulation.

The clay solution, which is under pressure in the well, cements the soil of the walls, thereby preventing the penetration of water, which eliminates the use of casing pipes. After completing the drilling of the well, if necessary, a reinforcement cage is installed into it, the concrete mixture from the vibrating hopper through the concrete-cast pipe falls to the bottom of the well, rising upward, the concrete mixture displaces the clay solution. As the well is filled with concrete mixture, the concrete pipeline is raised.

Currently, a special polymer concentrate based on polyacrylamide is being successfully tested, which, during the hydration process, forms a colloidal drilling fluid that creates a protective film on the walls of the well, which, in combination with excess hydrostatic pressure, prevents their collapse. Drilling in difficult geological conditions without the use of casing pipes showed the integrity of the bored pile throughout its entire depth after pumping concrete into it and the absence of any sagging or depressions of concrete on the side surface of the pile. The use of colloidal solution can significantly increase the productivity of drilling operations, reduce their cost and labor intensity, and sharply reduce the need for casing pipes without reducing the quality of work.

Fastening wells with casing pipes. Construction of piles using this method is possible in any hydrogeological conditions; casing pipes can be left in the well or removed from it during the pile manufacturing process (Fig. 3). Casing pipes are connected to each other using specially designed locks (if these are inventory pipes) or by welding. Wells are drilled using a rotary or percussive method. The immersion of casing pipes into the ground during the drilling of a well is carried out using hydraulic jacks.

Fig.3. Technological diagram for installing bored piles using casing pipes:

A- installation of the conductor and drilling of the well; b- immersion of the casing; V- drilling a well; G- building up the next section of the casing pipe; d- cleaning the bottom of the well; e- installation of reinforcement cage; and- filling the well with concrete mixture and removing the casing; 1 - working body for drilling a well; 2 - well; 3 - conductor; 4 - drilling rig; 5 - casing pipe; 6 - reinforcement frame; 7 - concrete pipe; 8 - vibrating hopper

After cleaning the face and installing the reinforcement cage, the well is concreted using the vertically moving pipe method. As the well is filled with concrete mixture, the inventory casing pipe can also be removed. A special system of jacks mounted on the installation imparts a reciprocating movement to the pipe, due to which the concrete mixture is further compacted. Upon completion of concreting the well, the pile head is formed. Installations for the production of cast-in-place piles using casing pipes with soil extraction from the pipe using a vibratory grab are used (Fig. 4).

Fig.4. Technological scheme for the production of cast-in-place piles with soil excavation under the protection of casing pipes:

A- immersion of the casing using a vibration installation; b- extraction of soil from the casing using a vibratory grab; V- concreting the pile; G- removal of the casing using a vibrating installation; 1 - casing pipe; 2 - vibration installation; 3 - vibratory grab; 4 - reinforcement frame; 5 - tub with concrete mixture

Bored piles with a widened heel. The diameter of such piles is 0.6...2.0 m, length 14...50 m. There are three ways to install widening piles. The first way is soil bursting strengthened tamping concrete mixture in the lower part of the well, when it is impossible to assess the quality of the work, the shape (what the widening heel has become), how much the concrete has mixed with the soil and what its bearing capacity is.

In the second method, a well is drilled using a machine that has a special device on the drill column in the form of a drop-down knife. To create a widening of the well with a diameter of up to 3 m (Fig. 5), the knife is opened by a hydraulic mechanism controlled from the surface of the earth. When the rod rotates, the knives cut off the soil, which falls into a bucket located above the expander. After several operations of cutting the soil with knives and extracting it to the surface, a widened cavity is formed in the soil. A clay solution made from bentonite clays is fed into the well, which continuously circulates and ensures the stability of the well walls. When constructing expansions, the cavity is drilled out simultaneously with the supply of fresh clay solution into the well until the solution contaminated with soil is completely replaced. After completion of drilling the well to the designed depth, the drill string with the expander is removed, and a reinforcement cage is installed in the well. Concreting is carried out using the vertically moving pipe method, when concrete mixture is simultaneously fed into the pipe and raised. The concrete mixture, in contact with the viscous clay solution, does not reduce its strength, and the cement binder is not washed out of the mixture. The concrete mixture squeezes the clay solution up the pipe and through the gap between the pipe and the well. The lower end of the concrete pipe must be permanently buried in the concrete mixture to a depth of about 2 m; Concreting is carried out continuously so that there are no layers of clay solution in the concrete.

Fig.5. Drilling a cavity in the soil with an expander:

A- position of the expander during drilling of the well; b- the same, in the process of drilling out the cavity; 1 - soil collector; 2 - cutting knives; 3 - well; 4 - rod; 5 - widened cavity

Explosive method expansion devices (Fig. 6). A casing pipe is installed into the drilled well. An explosive charge of estimated mass is lowered to the bottom of the well and wires are routed from the detonator to the explosive machine located on the surface. The well is filled with concrete mixture to a depth of 1.5...2.0 m, the casing pipe is raised 0.5 m and an explosion is carried out. The energy of the explosion compacts the soil and creates a spherical cavity, which is filled with a concrete mixture from the casing. After this, in portions and with the necessary compaction, fill the casing pipe with concrete mixture to the top.

Fig.6. Technological diagram for installing piles with camouflage widening:

A- lowering the explosive charge and filling the well with concrete mixture; b- lifting of a concrete pipe and formation of a widened heel by an explosion; V- finished cast-in-place pile with camouflage widening; 1 - explosive charge; 2 - wire to the blasting machine; 3 - casing pipe; 4 - receiving funnel; 5 - concrete mixture; 6 - tub with concrete mixture; 7 - widened heel; 8 - reinforcement cage

Bored pile with shoe. The peculiarity of the method is that a casing pipe with a freely supported cast iron shoe at the end is lowered into the drilled well, which is left in the ground after the casing pipe is immersed to the required depth. By loading the concrete mixture in portions, compacting it regularly and gradually removing the pipe from the well, a finished cast-in-place concrete pile is obtained.

Pipe concrete piles. The fundamental difference of the method is that a casing pipe up to 40...50 m long has a rigidly fixed shoe at the bottom. After reaching the bottom of the well, the pipe remains there, is not removed, but is filled with concrete mixture.

Underwater concreting used to protect concrete mixtures from erosion at high levels of low-moving groundwater. The concrete mixture is fed into the casing pipe not through a tray, but under pressure through a pipeline immersed to the very bottom of the well. Thanks to the pressure, the mixture is squeezed out of the pipe, fills the space of the well from below and begins to rise upward, pushing the water in the well upward. During the process of filling a well with a concrete mixture, it is necessary to ensure that the concrete pipe rises at the same speed as the casing pipe, the bottom of the pipe is always 30...40 cm lower than the top of the laid concrete mixture. After the well is completely filled, the top layer of the concrete mixture is 10... thick... 20 cm that was in contact with water is cut off.

In flooded soils, pressure concreting of cast-in-place piles can be used, which consists of continuously pumping a concrete mixture to the entire height of the well under the influence of hydrostatic pressure created by concrete pumps. Pressure concreting eliminates mixing of the concrete mixture with water, clay solution or slag (drilling materials). The injection rate is set based on the conditions of continuity of the process of concreting the pile and unimpeded removal of the casing after filling the well with concrete before setting begins. The mobility of injected concrete mixtures should be within 18...24 cm.

Pneumorammed piles. Piles are used when constructing foundations in water-saturated soils with a high filtration coefficient. In this case, the concrete mixture is placed into the cavity of the casing at a constant increased air pressure (0.25...0.3 MPa), which is supplied from the compressor through a receiver that serves to smooth out pressure fluctuations. The concrete mixture is supplied in small portions through a special device - a lock chamber, which operates on the principle of pneumatic injection units used to transport the concrete mixture. The airlock chamber is closed with special valves. The concrete mixture is supplied into the chamber with the bottom valve closed and the top valve open; When the chamber is filled with the mixture, the upper valve closes, the lower one, on the contrary, opens, and the mixture is squeezed into the well.

Cast-in-place piles of any type should be concreted without interruption. When the piles are located less than 1.5 m from each other, they are made one after the other, so as not to damage the newly concreted ones.

The missed wells are concreted during the second penetration of the concrete installation, after the previously concreted piles have gained sufficient strength and load-bearing capacity. This sequence of work provides for the protection of both finished wells and freshly concreted piles from damage.

Bored piles have a number of disadvantages that hinder their wider use. Such disadvantages include low specific bearing capacity, high labor intensity of drilling operations, the need to anchor wells in unstable soils, the difficulty of concreting piles in water-saturated soils and the difficulty of monitoring the quality of work performed.

The installation of piles in squeezed wells is quite effective in dry soils. When installing such piles in the ground, a compacted zone is created, the strength of the soil increases and its deformability decreases. The installation of cast-in-place piles in compacted wells is carried out using punching methods without extracting soil to the surface.

This work technology is based on the formation of a well by repeatedly dropping a cast iron cone from a height, as a result of which a well is drilled. Then the well is filled in portions with concrete mixture, crushed stone or sand and compacted until a widened part is formed at the base of the pile. In the upper part, when laying the concrete mixture, it is compacted by vibration. Many modifications of this method have been developed. The formation of wells and cavities in the soil without excavation is carried out by: punching with cores and casing pipes using hammers, punching with vibratory hammers and hammers, punching with projectiles and tampers, punching with pneumatic punches, expansion with hydraulic compactors, punching with screw devices.

Found a use stamping method using a cable percussion drilling machine (Fig. 7). First, a leader well is drilled to a depth of up to 1/2 the length of the future pile, then the well is pierced with an impact projectile to the required depth. Rigid concrete mixture is loaded into the lower part of the well in a column of 1.5...2 m and, with the blows of a rammer, a widened heel is created at the base of the pile. A casing pipe is installed at the wellhead, a reinforcement cage is installed, and the upper part of the pile is concreted.

Fig.7. Technological diagram of the installation of bored piles with a stamped heel:

A- well drilling; b- installation of casing pipe into the well; V- filling the well with rigid concrete mixture; G- compacting the concrete mixture into the base; d- removal of the casing pipe and installation of the reinforcement cage; e- concreting the pile shaft with compaction using an in-depth vibrator; and- installation of formwork for the pile head; 1 - drilling machine; 2 - working mechanism with attachments for constructing a widened heel; 3 - casing pipe, 4 - tray for loading rigid concrete mixture; 5 - rammer; 6 - jib crane; 7 - reinforcement frame; 8 - tub with concrete mixture; 9 - funnel; 10 - stamped widened heel; 11 - head formwork

The method of vibroforming piles is characterized by the presence of a vibroformer. Its hollow tip has blades at the bottom and is connected through a rigid rod to a vibrating hammer. Under the influence of the latter, the tip sinks into the ground and forms a well, which, as the tip sinks, is filled with a concrete mixture from a bunker installed above the wellhead. After drilling the well, the tip is raised slightly, while its blades open, and through the cavity of the tip, the concrete mixture falls to the bottom of the well. Instead of self-opening sashes, a loose cast iron shoe can be used.

Rammed piles are used in dry cohesive soils. Using a vibratory driver mounted on an excavator, a steel casing pipe with a removable reinforced concrete shoe at the end is immersed into the drilled well to the design mark. The pipe cavity is filled to 0.8...1.0 m with concrete mixture, compacted using a special tamping rod suspended from a vibrating hammer (Fig. 8). As a result, the shoe, together with the concrete mixture, is pressed into the ground, thereby forming a widened heel. The casing pipe is filled with concrete mixture in portions with constant compaction. As the well is filled with concrete mixture, the casing pipe is lifted by an excavator while the vibrating hammer is running, which significantly reduces the adhesion of the pipe to the concrete during its removal.

Fig.8. Technological diagram for the installation of rammed piles:

A- well formation; b- laying the first portion of concrete mixture; V- compaction of the concrete mixture with a tamping rod rigidly connected to a vibrating hammer; G- laying and compacting subsequent layers of concrete mixture; d- removal of the casing pipe and installation of the reinforcement cage at the head of the pile

Frequently rammed piles arranged by driving a casing pipe into a drilled well along with a cast iron shoe put on at the end, which remains in the ground (Fig. 9). The concrete mixture is loaded into the casing pipe in portions of 2...3 steps. The pile section is formed and the casing is removed from the well using a double action hammer that transmits forces through the casing.

Fig.9. Technological diagram of the installation of frequently rammed piles:

A b- installation of reinforcement cage; V- supply of concrete mixture into the pipe cavity; G- removal of the casing with simultaneous compaction of the concrete mixture; 1 - casing pipe; 2 - pile driver; 3 - double action hammer; 4 - reinforcement frame; 5 - tub with concrete mixture; 6 - receiving funnel; 7 - cast iron shoe

The casing pipe with a cast iron shoe is immersed into the ground under the influence of hammer blows to the design mark. As the pipe plunges, it pushes the soil particles apart and compacts it. When the pipe reaches the bottom point, a reinforcement cage is lowered into its cavity (if necessary), then a rigid concrete mixture with a cone draft of 8...10 cm is fed into the cavity of the casing pipe through a funnel from a vibrating bucket.

After filling the casing to a height of 1 m, they begin to lift it, while the shoe slides under the action of the concrete mixture pressing on it, which begins to fill the well. A double-action hammer connected to the casing produces frequent paired blows directed alternately up and down. From impacts directed upwards in 1 minute, the pipe is removed from the ground by 4...5 cm, and from impacts directed downward, the pipe settles by 2...3 cm. Compaction of the concrete mixture entering the well under the influence of its own mass is carried out due to impacts from the lower edge of the casing pipe and friction of concrete against the pipe walls as a result of the vibration impact of the hammer, therefore, the entire concrete mixture is constantly in the process of vibration and ultimately turns out to be well compacted. As a result, the soil in the lower part of the well is compacted, and part of the concrete mixture is pressed into the walls of the well, increasing their strength.

This compaction of concrete in the casing pipe continues until the pipe is completely removed from the ground. If necessary, external vibrators are attached to the removed casing pipe, which allow for better compaction of the upper layers of the concrete mixture. Frequently rammed piles can be made reinforced. Reinforcement is carried out according to calculation, but in most cases, the reinforcement cage is used only in the upper part of the pile to connect with the reinforcement of a monolithic grillage. If reinforcement is provided for the entire height of the pile, then the reinforcement cage is lowered into the casing before concreting begins.

Sand cast-in-place piles- the cheapest way to compact soft soils. A steel casing pipe with a shoe is immersed in the ground using a vibratory driver (Fig. 10). Having reached the design mark, it is partially filled with sand; when lifting the casing pipe, due to the mass of sand, it is separated from the shoe, and with the help of a vibratory loader it is removed to the surface, while the soil is compacted from vibration shocks. Additional and effective compaction can be achieved by flooding the well with water. Pipes with a diameter of 32...50 cm are used; When extracting, there should always be a layer of sand 1.0...1.25 m high in the pipe. The method is applicable for wells up to 7 m deep.

Fig. 10. Scheme of installation of sand (soil) cast-in-place piles:

A- immersion of the casing; b- pipe removal; V- drop-down tip; 1 - vibrating driver; 2 - casing pipe; 3 - hinge; 4 - tip flap; 5-ring

Soil concrete piles. Soil concrete piles have found use, which are installed using drilling rigs with a hollow drill rod, which has a mixing drill at the end with special blades that cut and simultaneously mix the mixture. After drilling a well in weak sandy soils to the desired level, a water-cement suspension (mortar) is fed into the hollow rod under pressure from a mortar mixing plant. The drill rod slowly begins to rise upward during reverse rotation, the soil is saturated with cement mortar and is additionally compacted with a drill. The result is a cement-sand pile, manufactured on site without excavation.

Screw-drilled piles. Often, pits for buried structures have to be built near existing buildings. Driving piles and sheet piling can lead to their deformation due to the resulting dynamic influences. When installing bored piles, where the immersion of the casing occurs with advanced removal of soil from the pipe cavity, leakage of the soil mass from under adjacent foundations is possible, which can also lead to deformations of existing buildings. The use of "wall in soil" methods or the use of clay mortar for immersing pipes leads to an increase in the cost of the project.

Fig. 11. Scheme of a drilled screw pile:

1 - metal pipe; 2 - welding of coiling with pipe; 3 - winding from reinforcement with a diameter of 10...16 mm with a pitch of 200...400 mm; 4 - cross-shaped blind or lost tip; 5 - cross; 6 - metal disk

With these methods, the natural underground environment and its balance are disrupted, which can lead to undesirable results or a serious increase in construction costs. In cases of dense buildings, it is advisable to use the method of drilled and screwed piles. The essence of the method is that the metal pipe is not driven into the ground, but screwed in (Fig. 11). In the factory, a narrow screw made of reinforcement with a diameter of 10...16 mm is wound onto the pipe in increments of 200...500 mm. Depending on the ground conditions, the pipe can be equipped with a plug with rippers, blind or loose, allowing, if necessary, to prevent water from entering the body of the pipe. When screwing the pipe, the surrounding soil is partially compacted, about 15...25% of it is squeezed out.

If the pipe is blind at the bottom, then after screwing to the design mark, a reinforcement cage is inserted into it and it is filled with concrete mixture. For pipes with a loose tip, a reinforcing cage is inserted into it, the pipe is filled with concrete, during the process of setting the concrete, the pipe is unscrewed, leaving a shoe in the ground on which the reinforced concrete bored pile rests. For particularly dense soils, it is possible to pre-drill a well to a slightly shallower depth (up to 1 m) and the diameter of the well should be less than the diameter of the pipe. The diameter of the screwed pipes is 300...500 mm, length from 4 to 20 m. It is important that the technology allows work to be carried out near existing buildings at a height of 5 floors at a distance of about 40 cm, at a higher height - about 70 cm.

In recent years, foundations in the form of powerful deep supports with high load-bearing capacity, constructed using special machines (Fig. 12), have become widespread. Soil development is carried out using a clamshell bucket inside a lowered casing pipe. During soil development, the lower end of the pipe must be below the bottom of the well. The face is cleaned using a grab bucket. After installing the reinforcement cage in the well, concreting is carried out using the method of a vertically moved pipe; The depth of the concrete pipe into the concrete mixture must be at least 1 m.

Fig. 12. Technological diagram for installing bored piles with a diameter of 2...3.5 m:

A- installation of a drilling rig; b- drilling a well; V- face cleaning; G- installation of reinforcement cage; d- installation of concrete pipe; e- concreting the pile; 1 - drilling rig; 2 - casing pipe; 3 - grab bucket; 4 - reinforcement frame; 5 - concrete pipe

2. FEATURES OF DESIGNING BORED PILES AND PILE FOUNDATIONS

2.1. The design and installation of bored piles is carried out in accordance with the requirements of SNiP 2.02.03-85 "Pile foundations", SNiP 3.02.01-87 "Earth structures, foundations and foundations", SNiP 2.03.01-84 "Concrete and reinforced concrete structures".

2.2. Loads and impacts, their combinations, reliability factors and operating conditions are determined in accordance with the requirements of SNiP 2.01.07-85 “Loads and impacts” and industry design standards.

2.3. Bored piles using imported equipment are reinforced with welded spatial frames. Longitudinal working reinforcement must be evenly distributed along the circumference. The number of rods must be at least 6, and the diameter must be at least 18 mm. The distance between longitudinal bars must be at least 40 cm. Longitudinal reinforcement bars should preferably be used from class AIII steel.

Reinforcing cages must have fixing elements made of plastic tubes with a diameter of 90 mm and a length of 70 mm, ensuring the required thickness of the protective layer of concrete, installed on transverse stiffening rings along the length of the pile.

2.4. In addition to the basic requirements set by SNiPs, the reinforcement cage must have a rigidity sufficient to immerse it in a well filled with concrete. For this purpose, it must be made welded with solid longitudinal rods bent into a cone at the bottom. If necessary, it is recommended to weld transverse stiffening rings in height increments of 2-3 m. It is preferable to have a minimum number of rods of larger diameter.

2.5. The protective layer of concrete must be at least 70 mm and ensured by installing clamps on transverse stiffening rings welded to the reinforcement frame.
; GOST 12730.5-84.

2.7. Changes in the design of foundations made of bored piles, caused by a discrepancy between the actual geological, hydrogeological and other conditions adopted in the project, must be made by the design organization with prior agreement with the customer.

2.8. Work on the installation of bored piles must be preceded by the planning of the construction site at a given elevation with the breakdown of the axes of the structure and reliable fixation of the position of the rows of bored piles on the ground.

2.9. The layout of the axes of structures should be documented in an act, to which are attached the layout of the layout signs, data on the connection to the base line and to the high-altitude support network. The correctness of the layout should be systematically monitored during the work process, as well as in each case of displacement of the points securing the axes.

2.10. Deviations of the alignment axes of rows of bored piles from the design ones should not exceed 1 cm per 100 m of row; in the position of single bored piles - ±0.05 of the pile diameter; for row or cluster arrangement of piles - ±0.15 of the pile diameter.

Deviations of pile heads from the design vertical position are allowed in the direction of overestimating the head elevation by up to 10 cm, and in the direction of underestimating it by up to 20 cm. In all cases, the embedment of the pile head into the grillage concrete (without taking into account preparation) must be at least 10 cm.

The tangent of the angle of deviation of the vertical axis of the pile from the design position should not exceed 1/100 (the deviation of the borehole wall from the plumb line position should not exceed 10 cm for every 10 m of borehole depth).

2.11. In winter, work on installing bored piles in waterlogged soils can be carried out at outdoor temperatures down to minus 10 °C.

Work on the installation of bored piles at lower temperatures is possible if special measures are taken to ensure the normal operation of the drilling rig, equipped with an on-board system for monitoring the main parameters of the technological process, with careful protection of freshly laid concrete from freezing. These activities must be indicated in the work organization project.

2.12. The materials used to prepare concrete for bored piles must meet the requirements of GOST standards for cementitious materials.

2.13. For the production of concrete mixture the following are used:

- cement for the preparation of concrete grade of at least 300, resistant to aggressive environments with a setting period of at least 2 hours. The use of aluminous, quick-setting and hot cements is not allowed;

- sand, crushed stone, gravel of fractions with a particle size of no more than 20 mm. The strength of gravel and crushed stone must be at least 800 kgf/cm;

- lignosulfonate concentrates (LST) in accordance with the “Guidelines for the use of chemical additives in concrete”. M., Stroyizdat, 1981.

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Bored pile foundation

When building a private house, in the presence of at least one of the factors: high groundwater level, weak bearing capacity of the soil, slight slope on the building site, large depth of soil freezing, large weight of the building being erected - more than 350 tons - it becomes impossible to install a conventional strip monolithic reinforced concrete foundation. Also, if the site has very heavy soils and the installation of a strip foundation is associated with high labor intensity of excavation work, the installation of pile foundations becomes preferable. The only disadvantage of installing pile foundations for a house is the lack of a basement.

Pile foundation calculation

When designing a pile foundation, it must be calculated for the expected loads. To do this, you need to know the weight of the entire building, the soil composition of the base and its bearing capacity to a depth of at least 4 meters. If the base consists of weak soil, then it is advisable to go through it to a stronger layer of soil. If the piles do not reach the solid layer, they are called hanging piles; if they reach it, they are called rack piles. Based on the accepted diameter of the pile and its length, its load-bearing capacity in a given soil is determined.

When designing a pile foundation, a calculation for the expected loads must be performed.

Next, knowing the total load on the soil and the load-bearing capacity of one pile, you can find the number of piles for a given house. The piles are installed under the load-bearing walls in increments of at least 2 m. A reinforced concrete grillage is placed on top of the piles, which can be either shallow or completely raised above the ground.

Types of pile foundations

At the moment there is a wide variety of pile foundations. According to the method of construction, they are divided into the following main types:

driving;
screw;
bored

Driven piles can be metal, wood and reinforced concrete. They are mounted using special impact driving mechanisms and hammers. The most common piles of this type are reinforced concrete with a square or polygonal cross-section; the ends of such piles have a pointed appearance. Piles of this type are usually used in industrial construction, as well as in the construction of large buildings for cultural and domestic purposes.

Screw piles are usually steel tubes with helical blades at the end. They are coated with durable anti-corrosion protection, which ensures their durability. Such piles are used in many types of construction; they have also gained great popularity in the construction of private houses and other not very large structures. A distinctive feature of this type of piles is that they can be installed independently, without resorting to complex construction equipment.

Bored piles are the name for drilled piles, which are made by drilling holes and filling them with compacted monolithic concrete with pre-installed reinforcement cages. The attractiveness of this type of piles lies in the possibility of installing them on your own and at low cost. Modern bored piles for a private home can be installed by two workers within a few days.

Tool used for making piles

To make a bored foundation with your own hands, you will need a certain tool:

laser level;
tape measure 10 and 50 m;
TISE-F hand drill or gas drill;
mortar mixer;
deep vibrator-mace;
box for prepared concrete;
wheelbarrow;
shovels and buckets;
mason's cord;
grinder and welding machine;
knitting wire;
wooden formwork for grillage installation;
circular saw or jigsaw for formwork;
hammer, axe, crowbar, roofing felt knife.

In addition to this tool, for each specific case you may additionally need something else. Usually, when building a private house, every home craftsman has most of this set of tools.

Technology for constructing a foundation using bored piles

Almost always, work on laying the foundations of any building, including a private house, begins with transferring dimensions from the drawing to the building site. To do this, you must have certain skills in working with drawings and measuring devices. In the simplest case, if the building has a rectangular shape in plan, you must first find the corner extreme points and secure them to the ground with wooden pegs. It is very important, in addition to the dimensions of the sides in meters, which are measured with a tape measure, that all angles formed by the sides of the house on the plan are straight, i.e. 90 degrees. In geodesy this is done using a theodolite, and in the construction of a private house they use the measurement of the diagonals of our rectangle. They must be identical with high accuracy, then all angles will be 90 degrees. This is a very simple and effective way to lay out a building in plan without using a theodolite.

How to mark a pile foundation

After securing the four corners of the rectangular building to the ground, a cord is pulled between them - this can be done using thick fishing line or thin stainless wire. Then, using a tape measure, determine the location of each pile, according to the construction drawing of the pile field plan, which is included in the overall design of a private house.

Before construction begins, the design for the entire building being constructed must be in hand. After determining the points for all piles, the building axes are rigidly secured in two mutually perpendicular directions. This is done using the so-called cast-off, which is located 1.5–2 m further from the marked points for the piles. The carrying device is a U-shaped structure, two legs of which are buried in the ground, and a horizontal crossbar is attached to them. The location of the axis of the building is fixed on it with a nail or pin. This stripping is carried out on all four sides of the building opposite each alignment axis. By pulling the axial cords between the pins on the castoffs, we obtain the location on the ground of all the piles that need to be installed.

Before drilling begins, the diameter of the piles, the depth of immersion in the soil and the drilling method must be determined. In private house construction, both manual and mechanical drills are used, which are installed on specialized machines. In addition, there are also gas drills, which greatly speed up the drilling process using gasoline engines. However, the simplest option is a TISE manual drill, which makes it possible to drill a hole for a pile with a diameter of 280 mm and a length of up to 2 m. For the construction of an ordinary two-story house, this drill is quite enough. This hand drill, which was invented by a designer from Moscow, has an additional device called a plow, which allows you to make an expansion at the bottom of the pile - the heel - up to 500 mm in diameter.

Of course, the manual drilling process is quite slow, which also depends on the strength of the soil. In one shift, you can drill from 2 to 6 wells up to 2 m deep. However, this type of foundation is much easier to implement, including from an economic point of view, than a traditional deep strip foundation.

Installation of formwork

After completing the excavation work - drilling wells for all the piles - they begin to manufacture and install the formwork for the piles. Usually they use the most economical option - this is roofing material rolled into a tube and secured with tape. Such pipes are made for all wells. For sections of piles located above the ground at a height of 300–400 mm, roofing material is used, tied on the outside with knitting wire or plaster mesh, and plastic pipes of the appropriate diameter can also be used. Throughout the entire period of time from drilling wells to installing the formwork, the accuracy of the location of the piles according to the markings is strictly controlled using axes. To prevent the upper part of the pile, which is located above the ground, from moving to the side during the concreting process, two guides made of wooden blocks are used, which are secured at the ends to the cast-offs with nails and act as guides for the upper parts of the pile formwork. Before concreting, you can prepare the formwork for one row of piles. After concreting them, move on to the next row.

Pile reinforcement

All bored piles are monolithic reinforced concrete structures that are manufactured directly at the construction site. Each pile is reinforced with a frame of class AIII steel reinforcement; usually the longitudinal reinforcement has a diameter of 10 to 14 mm, and the transverse distribution reinforcement has a diameter of 5 to 6 mm. Transverse reinforcement can be made of smooth wire in the form of clamps. Frames are usually welded and manufactured in parallel with drilling wells, so that after installing the formwork, the reinforcement can be quickly installed and prepared for concreting. The frames are made in such a way that there is a release of approximately 350-400 mm of reinforcement over the concrete surface after concreting. This is necessary to connect the grillage frames and piles.

Reinforcement and formwork of foundation piles

Pouring concrete

To concrete the foundation on the site, a concrete mixture of sand, crushed stone and cement with water is prepared in a concrete mixer in proportion to obtain M300 concrete. Proportions are easy to find in reference books or on the Internet. They bring ready-made concrete to the piles with a wheelbarrow and, using a ladle or trowel, throw the concrete into the formwork, while vibrating it using an in-depth needle vibrator - this applies to the part of the pile that is located in the ground. The part of the pile above the ground is concreted without vibration. In order for the concreting process to be successful, it is best to install piles in spring, summer or autumn at positive outside temperatures.

Grillage arrangement

All pile foundations during the construction of a house are completed by installing a grillage along the top of the piles. In this case, the reinforcement frame of the grillage is connected by welding to the working reinforcement of the piles. The grillage formwork is made of wooden panels. The width and height are taken from the project. In this case, the width is 400-500 mm, so that along the upper cut of the grillage it is possible to lay brickwork for the load-bearing walls of the house. Such a foundation is more economical in terms of consumption of concrete and reinforcement than a conventional strip foundation laid below the freezing level of the soil. If the grillage is made shallow, the formwork is installed on both sides - internal and external. If the grillage according to the design should be located above the surface of the ground, then the formwork is also placed on the lower part of the grillage. After installing the formwork, the reinforcement frames are installed and tied to the pile frames. After all the work on installing the formwork and frame, the top level of concrete is beaten. After this, the M300 concrete mixture is prepared and poured with vibration. After the concrete has been cured for at least a week, the formwork is dismantled and the grillage is waterproofed with bitumen mastic. Now almost everything is ready for the construction of walls and flooring on the first floor. This is how you make a bored foundation with your own hands.

IC "Installation of Pile" is engaged in the construction of foundations on reinforced concrete piles. We are ready to equip a reliable turnkey foundation at the lowest cost in Moscow, completing all work in strict accordance with the requirements of SNiP in the shortest possible time. To cooperate with the company, fill out the “Leave a request” form located at the bottom of the site.

This article provides detailed instructions for manual installation of a foundation made of bored piles. We will consider all stages of creating a foundation - from its design and marking to pouring piles and tying them with a reinforced concrete grillage.

Independent foundation design

The first stage of arranging any pile foundation is its design, during which it is necessary to determine the load-bearing capacity of the reinforced concrete support and the total loads on the foundation, and based on them, calculate the required number of piles for building a house.

Important: the load-bearing properties of a pile are always determined “by the soil”, since the load-bearing characteristics of concrete as a material exceed those of the soil. For example, 1 sq. cm of M100 concrete can withstand a standard load of 100 kg/sq.cm, while 1 cm2 of clay soil, which is prevalent in the Moscow region, holds no more than 6 kg/cm2.

Fig 1.1

To find out the load-bearing properties of the soil, it is necessary to conduct geodetic surveys at the construction site. During their implementation, geodetic wells are drilled, from which soil samples are taken for laboratory analysis. The price of the service depends on the depth of soil development - from 2 to 3 thousand per 1 linear meter of well (the price includes the cost of laboratory work).

We offer you an average calculation of the load-bearing properties of piles based on clayey soil common in Moscow. The table shows the characteristics of piles with a diameter of 15-40 cm typical for individual construction.

Figure 1.2

To determine the number of piles in the foundation, you need to calculate the total mass of the building, which is done by multiplying the area of the structural elements of the building by the standard weight of building materials given in the following table:

Rice. 1.3

The following loads are added to the resulting mass of the building:

Useful operating load - 100 kg per sq.m. floors of the house (ground and interfloor);
Snow load on the roof (depending on the region of construction).

Rice. 1.4: Map of snow loads of the Russian Federation

The total sum of loads is multiplied by 1.2 (safety factor), after which the result is divided by the load-bearing capacity of one pile. This determines the required number of supports in the base.

The pile placement scheme is drawn up as follows:

The minimum distance between supports is 1 m, the maximum is 3 m;
It is necessary to have piles at the points where the walls join at the corners of the building and at the junctions of the internal and external walls;
The supports are deepened below the depth of soil freezing in a given region (to avoid negative loads from soil heaving).

Rice. 1.5: Map of soil freezing in Russian regions

Preparatory work

Before starting the installation of the foundation, it is necessary to purchase the required consumables - concrete, reinforcement and planed boards for installing the formwork under the grillage. The standard consumption of concrete and reinforcement for typical configurations of bored piles is shown in Figure 1.1

To build a bored foundation yourself, you will need the following tools and materials:

For marking - reinforcing bars, planed boards and bars, construction cord or twine, self-tapping screws, level, tape measure;
For the installation of reinforced concrete piles - a concrete mixer, shovels, a hand drill, buckets, rolled roofing felt, tape, a wheelbarrow for removing soil;
To create reinforced frames: welding machine, grinder, reinforcing bars (corrugated, 12-15 mm in diameter, and smooth, 8-12 mm in diameter);
For the grillage - ready-mixed concrete in the required quantity, boards for formwork, hacksaws, nails and screws, electric drill, wire, waterproofing material for the grillage to cover after pouring.

Important: Initially, it is necessary to prepare the construction site - remove surface vegetation, debris, stones and boulders that may interfere with the work. If there is a sloping terrain, the site is leveled to one level.

Do-it-yourself foundation marking

To mark the base, it is necessary to knock down stripping boards from planed boards and beams. The structure consists of two horizontal belts, the first of which is used to lay out the zero level of the piles (their height), the second - to break out the upper edge of the grillage.

Rice. 1.6

Initially, the base lines of the foundation (the contours of the walls of the building) are marked - the distance is counted from the landmark (fence or site boundary) and the cast-off of the first wall is installed, a string is pulled between the boards (the thread is fixed using a self-tapping screw screwed into the board).

An adjacent wall is marked perpendicular to the laid contour. The right angle is checked using the Egyptian triangle (a distance of 3 and 4 meters is given on intersecting laces, a mark is made with electrical tape and the length of the diagonal is measured - at the correct angle its length is 5 meters).

Rice. 1.7

Next, the two remaining walls are marked in the same way. At a distance of the thickness of the grillage, a second cord is installed on the cast-off, defining the internal contour of the walls. The positions of the piles are marked according to their design distance from each other - casting boards are installed and a plumb line is lowered from the intersection of the string, under which a reinforcing peg is driven in, which determines the installation location of the pile.

DIY installation of bored piles

After marking the foundation, the stretched twine is dismantled and only the pegs are left in the places where the piles are arranged. The technology for creating supports is implemented in the following sequence:

Using a hand drill, holes are drilled for piles. It makes sense to go through all the wells at once, so that in the future you can fill the supports with concrete in one go;
A cylinder equal to the diameter of the pile is formed from rolled roofing felt, which is fastened with tape. The cylinder in this case acts as the pile formwork, so its height should be equal to the full length of the reinforced concrete structure (if necessary, protrude from the well). Once created, the formwork is placed inside the cavity;

Rice. 1.8

Reinforcing bars in the amount of 4-8 pieces are inserted into the wells (depending on the diameter of the pile). The rods are immersed in the ground so that the soil securely fixes them. The length of the reinforcement should be 30-40 cm greater than the length of the pile, protrusions are necessary for joining with the reinforcement frame of the grillage;
A concrete mixture is poured into the prepared wells (concrete grades M200 or M300 are used). You can prepare the mixture yourself using a concrete mixer or order ready-mixed concrete in the required quantity;

Rice. 1.9

After pouring, the concrete is bayoneted with reinforcement, which is necessary to remove air cavities formed in it from the mixture.

Important: Having formed the concrete body of the piles, it is necessary to wait 20-30 days before subsequent work, during which the structures gain standard strength.

Self-installation of reinforced concrete piping

Before arranging the grillage, it is necessary to restore the base lines dismantled for installation of piles on the cast-off. In this case, the twine is stretched along the upper horizontal belt, which is responsible for the level of the grillage.

Wooden formwork is installed along the contours of the trim. Initially, you need to install U-shaped load-bearing elements made of timber between bored piles, after which the outer contour of the formwork is sheathed with boards knocked into a shield.

Rice. 2.1

After forming, the formwork walls are covered with waterproofing material and work begins on installing the reinforced frame. On the reinforcement protruding from the piles, horizontal rods are fixed, raised to a height of 5 centimeters, to which pre-prepared rectangular clamps are welded.

Rice. 2.2

The side contours of the clamps in this case perform the function of transverse reinforcement. The number of longitudinal belts is selected based on the width of the grillage; for tying a standard width of 40 cm, 4 belts are used.

Important: each side of the reinforcement cage should be placed at a distance of 5 cm from the walls of the formwork, since when the reinforcement leaves the concrete body, the frame will be subject to accelerated corrosion.

The upper contour of the longitudinal reinforcement is welded to the transverse clamps. Pay special attention to strengthening corner joints - cross-joining is not allowed here.

Rice. 2.3

Correct joining of corners is carried out according to the diagram below - L-shaped reinforcements should be used on both the lower and upper chords of the longitudinal reinforcement.

Rice. 2.4

After installing the reinforced frame into the formwork, elevation marks are made on the inner surface of its walls, which determine the level of filling of the form with concrete. To fill the frame, we recommend using ready-mixed concrete purchased in the required quantity (intermediate hardening of the layers of the grillage body is not allowed, as it leads to a decrease in the final strength of the structure).

Rice. 2.5

Upon completion of pouring, the concrete must be pierced with reinforcement (to remove air cavities from the mixture) and the formwork must be covered with oilcloth. During the hardening process, which occurs within 25-30 days, the concrete must be periodically moistened with a hose and sprayer. Removal of the formwork structure is carried out two weeks after pouring the grillage.

Do-it-yourself installation of a pile foundation - video

Video #1 -

Video No. 2 - Arrangement of bored piles with your own hands (Part 1)

Arrangement of bored piles with your own hands (Part 2)

Video #3: Do-it-yourself formwork for grillage

Video #4 - Grillage reinforcement

Video #5 -

Bored pile foundation

When building a private house, if at least one of the factors is present: a high groundwater level, weak bearing capacity of the soil, a slight slope on the building site, a large depth of soil freezing, a large weight of the building being erected - more than 350 tons - it becomes impossible to install a conventional strip monolithic reinforced concrete foundation. Also, if the site has very heavy soils and the installation of a strip foundation is associated with high labor intensity of excavation work, the installation of pile foundations becomes preferable. The only disadvantage of installing pile foundations for a house is the lack of a basement.

Pile foundation calculation

When designing a pile foundation, a calculation for the expected loads must be performed.

Types of pile foundations

At the moment there is a wide variety of pile foundations. According to the method of construction, they are divided into the following main types:

driving;
screw;
bored

Tool used for making piles

To make a bored foundation with your own hands, you will need a certain tool:

laser level;
tape measure 10 and 50 m;
TISE-F hand drill or gas drill;
mortar mixer;
deep vibrator-mace;
box for prepared concrete;
wheelbarrow;
shovels and buckets;
mason's cord;
grinder and welding machine;
knitting wire;
wooden formwork for grillage installation;
circular saw or jigsaw for formwork;
hammer, axe, crowbar, roofing felt knife.

In addition to this tool, for each specific case you may additionally need something else. Usually, when building a private house, every home craftsman has most of this set of tools.

Technology for constructing a foundation using bored piles

How to mark a pile foundation

Installation of formwork

Pile reinforcement

Reinforcement and formwork of foundation piles

Pouring concrete

Grillage arrangement

It is cost-effective to install bored piles only on clay soils with a low level of groundwater level, the occurrence of the bearing layer is not lower than 3 m. Already at 5 m, drilling wells with a diameter of 0.5 m or more becomes more expensive than manufacturing a pile-screw foundation or a floating slab.

Initially, in the literature and construction, piles were clearly distinguished by the method of their immersion:

support pile - the formwork is mounted on the bottom of the pit/pit, after stripping the concrete structure is backfilled;
pile-pillar - a composite, wooden, reinforced concrete element is installed in the well;
drilling injection - supplying concrete with fine filler under pressure into a small-diameter well;
driven - the well was made not by drilling, but by compacting the soil with a special tool, reinforced, filled with concrete;
drilling - a drilled well with reinforcement installed inside is filled with concrete;
driven - the reinforced concrete product is pressed, driven in or immersed by vibration.

Currently, the installation of bored piles in private housing construction is carried out using the drilling method, and such piles should be called boring, but among individual developers the name bored pile has taken root. Therefore, we will continue to use the established concept - bored piles, but keep in mind that from a professional point of view, this name is not correct.

Geological surveys and calculations

According to the set of building rules SP 24.13330 regarding pile foundations, drilling and probing are mandatory geological survey operations for any cottage. An exploration well is necessary to take soil samples from different depths. The type of sensing (dynamic or static) is chosen based on the specific conditions of the project.

In the presence of man-made, loose, organic, weak, subsidence soils, the exploration well must penetrate through them. Unlike expensive geological surveys (budget from 30 thousand rubles), there is a technology for trial screwing in a screw pile with your own hands. In this case, it will not be possible to determine the thickness of each layer and the composition of the soil. But it is possible to determine the depth of the formation with its bearing capacity.

If it does not exceed 3 m, pillar piles can be included in the project; when calculating, only the soil resistance under the heel of the pile is taken into account. Substitute the minimum possible coefficient into the formula for soil resistance on the lateral surface, ensuring a safety margin for the foundation.

Unlike a strip foundation, grillage technology does not allow communications to pass through it. Engineering systems are launched under the foundation, at least 0.5 m from the piles. If it is not possible to maintain the specified distance, the pipeline is laid in a cage and concreted in a trench for a length equal to three diameters of the pile in each direction.

The ground grillage technology is the simplest:

there is no lower deck;
To lay concrete, it is enough to rest the side panels on the ground, strengthening them with jibs and spacers.

However, in this case, the foundation can be destroyed by heaving forces trying to raise the grillage beams in winter. To avoid this, the fertile layer under them is removed to a depth of 10–20 cm, and the trench is filled with sand. After stripping, the sand is removed from under the grillage, the space is protected with sheet material to prevent it from being filled with earth if it accidentally falls off. This free space guarantees protection against heaving forces.

With a shallow grillage, removing sand after stripping is very inconvenient - you have to dig out the foundation from both sides. Therefore, another technology is used - a 5 cm layer of foam with a minimum density. During soil swelling, this material contracts and later partially restores its shape.

Using the above technology, a home craftsman will independently build a foundation from bored piles with a strip grillage without errors. The technology allows you to save 30–40% of the budget compared to other foundations.

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When choosing the type of foundation, be sure to take into account the characteristics of the soil at the construction site. If you need to build a building without a basement on difficult soils, then a pile foundation would be an almost ideal option. This type of foundation is also more economically profitable, since its construction requires less building materials than usual. To build reinforced concrete piles, special formwork is required. Most often, this is a permanent form made of thick cardboard or PVC.

For the construction of small buildings weighing no more than 130-150 tons, foundations on bored piles are often used. This type of foundation is chosen for construction on difficult soils - loose, oversaturated with moisture, etc.

To build piles, a well is pre-drilled, the depth of which exceeds the depth of soil freezing in a given area by at least 50 cm. After which formwork is installed in the well and the piles are concreted. The cost of bored foundations is lower than monolithic strip foundations, so this design is often used in private construction.

Features of a pile foundation

A pile is a reinforced concrete rod, which is made by pouring concrete mortar into a formwork installed in a hole or driving the finished rod into the ground. Foundations consisting of piles have many advantages, including:

No need to dig a pit;
Limited material consumption.

However, the most important advantage of such a foundation is that it can be used for the construction of buildings on difficult soils:

If the top layer of soil is weak (sand), then the use of pile foundations allows the load exerted by the building to be transferred to the lower and denser layers of soil.
If a house is being built on dense soils, then the use of this technology can reduce the amount of labor-intensive excavation work.

Types of piles

Several types of piles are used in the construction of foundations:

Drivers;
Screw;
Printed.

The first two options for piles are used in private construction quite rarely, since driving concrete pillars requires the use of special mechanisms.

The process of installing bored piles is much simpler; they are made directly in the ground. A well is drilled, then formwork is installed - cardboard or PVC. Next, the reinforcement is installed and concrete is poured.

Types of formwork used for bored piles

The simplest method for making bored piles does not involve the use of formwork. The concrete solution is poured directly into the prepared wells. However, this method of construction is not the most rational.

The fact is that in order for concrete to gain strength, it is important that the content of “cement laitance” in the mass is sufficient. When pouring concrete mortar directly into wells, the “milk” is absorbed into the soil, so the concrete cannot gain the required strength.

To eliminate such “leakage” of liquid, self-production of the simplest formwork from roofing felt is used. The material is simply rolled into a tube and inserted into the well.

Today it is possible to simplify the work of constructing bored piles. For construction, permanent formwork made of cardboard or polyvinyl chloride, or removable formwork in the form of a metal or plastic pipe is used.

Permanent formwork options

Inexpensive and sufficient for the construction of bored piles is the use of disposable cardboard formwork. This is the simplest formwork, which consists of a polymer base wrapped in a spiral with thick cardboard.

To prevent cardboard formwork from absorbing moisture, it is covered with a layer of waterproof polymer glue. Technical characteristics of cardboard formwork:

The diameter of the cast structure can vary widely from 15 cm to 1.25 meters.

Advice! Recently, cardboard formwork of not only round, but also square or rectangular sections has appeared on sale.

The wall thickness of the formwork can vary between 3-15 mm, depending on the diameter
Cardboard permanent formwork is available in lengths up to 11 meters.
The weight of formwork forms, depending on the diameter, ranges from 1.8 to 9 kilograms per linear meter.

Advice! Due to its low weight, permanent cardboard formwork can be installed without the use of lifting equipment.

Removable formwork

Removable formwork can also be used for the construction of bored piles. Such forms are represented by pipes made of steel or plastic of the appropriate diameter. The forms are installed in prepared wells, filled with concrete, and after 2-3 hours they are pulled off the cast structure.

A two to three hour soak, as a rule, is enough for the concrete to “set” a little, and in the future the piles will not change their shape and size. This construction technology has a disadvantage - the piles being built are not waterproofed from the surrounding soil.

To somewhat compensate for this disadvantage, it is recommended to make a sand layer between the surfaces of the piles and the sides of the wells. This will reduce the negative impact of freezing soil on the piles. If necessary, using removable formwork of different diameters, you can create piles with an expanded base, cone-shaped piles, etc.

How is a pile foundation built?

The construction of a foundation with the installation of drilled wells is carried out as follows:

Well preparation

Well drilling can be carried out using a hand drill or an electric drill.
The dimensions of the wells are determined by the project. It is important that the well depth is sufficient to penetrate weak soil layers. In addition, it is necessary that the depth of the well exceeds the freezing depth of the soil in the given area by at least 50 cm.
The width of the well is determined by the design diameter of the pile and the need to fill with sand.

Installation of formwork

Formwork should be installed in the prepared well. This can be cardboard or plastic formwork, which is not removable and will serve as waterproofing. Or it will be removable formwork in the form of a pipe of suitable diameter.

The formwork is installed in prepared wells, and sand is poured around the formwork. The functions of the sand layer are to protect future foundation piles from movements of freezing soil.

Performing reinforcement

To strengthen structures under construction, reinforcement is used. To create a frame, you should use 3-4 metal rods with a diameter of 6-8 mm. Along the length, the stubbles are fastened every half meter. The length of the reinforcement cage should be such that after installation in the well it protrudes 3 cm above the soil level.

The frame must be installed so that the distance between the reinforcement and the formwork walls is at least 2 cm. This will ensure the formation of a protective layer of concrete for the reinforcement, which will prevent corrosion processes.

Concreting

Concreting is carried out in layers, the height of the layers is 40-60 cm.
After laying the next layer, it is necessary to compact the concrete mixture using a vibrator or manually (bayonet).
It is important that the process of concreting the pile is continuous. If the previous layer of concrete has time to harden before the next layer is poured, the pile will not be solid.

So, different formwork options can be used to construct a pile foundation. The choice of the best one is made depending on the foundation design and the type of soil at the construction site.

A pile foundation is a fairly simple to manufacture and reliable type of foundation for a bathhouse. On suitable soils, it is good for light buildings, which are almost all bathhouses (except brick ones). This type of base is popular because it requires the least amount of materials, time and effort, and much less money. It is easy to do it yourself even without any special construction skills. But they cannot be installed on all soils. Designers are not very fond of them, because on heaving soils the effect of horizontal heaving forces on piles is poorly calculated.

If you still decide to build a foundation on piles, it is better to play it safe and take into account the worst forecasts. Take into account the most pessimistic data on soil freezing (you need to drill below the freezing depth) and loads. By drilling holes more often and making the distance between adjacent supports smaller, you will spend more money, but you will get a stable foundation. Having laid a certain margin of safety, one can hope that it will stand for a long time.

On unstable, loose, peaty and swampy soils, a pile foundation is the only possible option. It allows you to transfer the load from the house to dense layers of soil located below

Most often, pile foundations are made on soils that cannot ensure the stability of the building. These are quicksand, sand, peat bogs, and unstable loams saturated with moisture. In this case, the piles are lowered to the level of dense soil layers. The entire load from the building is transferred to these layers.

It is recommended to use this base on soils with a freezing depth of more than 1.5 meters. The construction of a strip foundation in this case is associated with large volumes of earthworks. Installing piles is much easier and cheaper.

Another option when it is convenient to use this type of base is in areas with complex terrain. Sometimes leveling the site for a house requires too much money. Then the piles also help out.

The third option for using a pile foundation is soils that are too dense and difficult to process. Digging a pit in them is very difficult and expensive. Drilling wells requires less forks and time.

Design

In places of frequent flooding, on the banks of reservoirs, they tried to raise houses above ground level. To do this, they drove in logs pointed at one end, which were located at each corner of the building, and also supported walls and partitions. This was the pile foundation. They used hard wood for the piles, which could resist water for a long time. The best wood for this is larch, because water only makes it stronger. The palaces and houses of Venice have stood on larch trunks for several centuries.

Today, wooden piles are used very rarely, although the result is the cheapest, but at the same time reliable foundation. Moreover, even where larch is not uncommon.

Types of piles

In total, builders distinguish twelve types of piles. But in low-rise construction only three are used:

Reinforced concrete columns are rarely used for the construction of a bathhouse or summer house: equipment is needed that will drive them into the ground. But the foundation turns out to be solid.

Screw iron piles are good because they can even be screwed in by hand. Their disadvantage is that steel is an excellent heat conductor. If the underground is not insulated, they take away heat, and the floor under your feet always remains cold.

If you make a pile foundation with your own hands, then in most cases the supports are made using bored materials. Although it requires the most labor, it allows you to save on materials.

Location

The supports must be placed in key places: at angles, at the junction with the walls. Intermediate piles are then installed between these nodes. The distance is selected based on the type of soil and planned loads, but it cannot be more than 2 meters. There must be supports around the perimeter of the walls, as well as under all piers.

Dimensions

The most common diameter of piles is 20 cm. It is undesirable to make them smaller, since their load-bearing capacity becomes much less. A larger diameter means a greater load-bearing capacity, but the area to which winter heaving forces will be applied also increases (on heaving soils). There are two options for determining the required pile depth:

In each area and even in each area the depth will be different. If the level of freezing is determined by region, then dense layers can be located in any way. If necessary, test drilling is carried out nearby, below the achieved level, to make sure that there are no cavities or pockets below and that the support will be reliable.

With and without grillage

In some cases, the piles are connected to each other into a single structure using wooden beams or a square steel pipe (sometimes an angle). This frame is called a grillage, and the foundation is called a pile-grillage. This strapping is needed if the walls are made of blocks, bricks or frames, and is not at all necessary if there is a log house.

How to make a foundation on bored piles

The first step is to mark the perimeter of the future building on the site. Then it is very advisable to remove the top layer of soil with vegetation over the entire area and fill it with crushed stone. Many people don’t do this; as a result, the plants under the house rot and spread “odors.” Even worse, parts of the rot can get onto the wood, and this contributes to its spread (maybe impregnation will protect, but why take the risk).

Then, using pegs and cords stretched between them, mark all the lines along which the piles will be located. In this case, you need to ensure that the marking pegs are placed vertically (usually with help). You also need to check that the laces are stretched horizontally (this is already done with help). Having arranged everything, measure the diagonals of all the rooms. Deviations should be minimal - a few millimeters, no more. This is the only way to be sure that during construction everything will be as it should be.

It all starts with ground work - removing the soil, then you need to mark the house plan with pegs and cords

Calculation of the number of piles

To lay the foundation, wells are drilled around the perimeter, into which piles are then installed (poured/driven). The number of piles for each project will be different. When building and planning with your own hands, proceed from the following rules:

The distance between piles should not be more than 2 meters.
Be sure to have supports at the corners of the building, as well as in places where partitions extend away. Next, place supports between these nodes, based on the fact that the distance between them should be less than 2 meters.

But 2 meters is for a one-story bathhouse made of light materials. If you are going to install a bathhouse on two floors, you need to install supports more often. The distance is also affected by the bearing capacity of the soil. If it is dense, you can place it less frequently; if it is loose or unreliable (peat, wooded soil), place it more often.

The depth of wells on heaving soils is calculated based on the depth of soil freezing in winter: 30-50 cm must be added to this value. When installing a pile foundation on unstable soils, the installation depth of the supports depends on the depth of the dense layer that can withstand the load. The support should fit into it at least the same 30-50 cm.

Well preparation

Wells are made at the locations of the piles. When building private small houses/dachas and bathhouses, this is done using hand drills. Their diameter is about 20-30 cm. Choose the one you see fit. The drill handle is usually composite, which is why you can use it to make holes up to 4-6 meters deep.

Bored piles come in two designs: with an expanded base (heel) and without. The “heel” located below increases the chances that the building will not move during heaving. Therefore, it is advisable to make such an extension. There are drills with a folding knife for this. When you reach the desired depth, release the wide knife by pulling the special lever.

Several buckets of crushed stone and sand are poured into the drilled wells and compacted (alternately, first crushed stone, then sand). On top of the sand layer is concrete with a gravel backfill, which will serve as a support (sole or heel - whoever says what).

Before the solution hardens, formwork is immersed in it, into which a reinforcing frame is then inserted and the whole thing is filled with concrete.

Formwork for bored piles

It is not so important what material the frame into which the concrete will be poured will be made of. The most common option is asbestos-cement pipes (diameter greater than 200 mm).

The use of asbestos-cement pipes is not necessary, but it is desirable: they do not rot, have sufficient strength, and their outer surface is smooth enough, which allows the piles not to change their position when the soil swells (i.e. your bathhouse will not tilt).

Advice:It is advisable to coat the underground part of the asbestos-cement pipe with a mineral-based (construction) lubricant. This will prevent the pipe from freezing to the ground.

Instead of an asbestos pipe, you can install a steel pipe (you never know, maybe someone has a lot of them), but they must be well primed and painted, otherwise they will quickly rust and collapse.

Some people use plastic sewer pipes of suitable diameter as formwork. The choice is not bad: they tolerate being in concrete and are not afraid of moisture. The surface is very smooth and slippery, which will not allow horizontal heaving forces to move them from their place.

There is another option for piles: make formwork from roofing felt. This material is wound in two or three layers, fastened and used as a frame. To make your work easier, you don’t have to worry about the diameter of the pipe every time, find yourself a pattern. It is more convenient to wrap the roofing material onto a large-capacity water bottle. The main thing is to find the appropriate diameter. Having rolled several layers, you fix the roofing material, and take out the “pattern” by the handle and you can make the next post.

It’s just not very convenient to fasten roofing felt. Previously, they used wire, but it is easy to pinch, and its area is small. More convenient with tape. Only he doesn’t want to stick to the sprinkles. Helping the problem is simple: use a stiff brush to clean off the crumbs in the right places (if there are any), then wipe with white spirit. After drying, the tape sticks perfectly.

Sliding formwork can be used. To do this, a pipe with a diameter of at least 20 cm is formed from a sheet of iron, plastic, thick cardboard or roofing felt. Handles are attached to the top of it. The formwork is lowered into the hole, reinforcement is inserted, the space around it is filled with coarse sand, and it is thoroughly compacted. Concrete is poured inside the formwork. Shaking the formwork, lift it up by the handles by 40 centimeters. Add sand from the outside, tamp it down, and pour the next portion of concrete. This is how the pile is prepared for its entire length. This, of course, is a very economical option, but in terms of strength and reliability it is much inferior to piles with any formwork. The fact is that without a protective layer, cement laitance can (and usually does) leak into the soil. As a result, the concrete has insufficient strength.

Reinforcement

To give the piles greater strength, three or four reinforcement bars are inserted inside. Diameter 8-10 mm (you can play it safe and take 12 mm, but this is clearly overkill). They are tied together with thinner reinforcement and knitting wire to form a frame. The distance between the longitudinal rods is chosen such that they are all at least 5 cm from the wall. (How to knit reinforcement).

Pouring concrete

This structure is installed inside the pipe. The space around the pipe is covered with soil or crushed stone with sand, compacting it thoroughly and making sure that the pipe stands vertically.

The last stage in the manufacture of a bored pile is filling the pipe with concrete. For this purpose, a cement-sand mortar is usually made. Its composition is as follows: for 1 part of cement (grade no lower than M300), take 3 parts of medium-grained sand, mix it all dry. Then water is gradually added. Its quantity is slightly less than 1 part: the solution should be like thick sour cream.

To increase the strength of concrete, it is necessary to remove air that could get into the solution. To do this, take a long pin (reinforcement rod), pierce the freshly poured solution, then rock the rod from side to side. Do this on each support several times. As a result, air escapes, the solution settles a little, it must be added to the required level.

Immediately try to make piles of the same height - there will be less work later. It is much easier to remove/add a little bit of fresh solution than to knock off/cut off the excess later. Having made them all the same, level the surface. Grinding hardened concrete is also not the greatest pleasure.

It is better to process the mortar in piles using a submersible one. In addition to increased strength, it will also become frost-resistant.

Finishing work

A cap is installed on top of the finished pile - a sheet of steel, on which roofing felt can then be laid. Actually, that's all. The pile foundation created by yourself is ready. If necessary, attach a grillage (beam 200*200 mm or larger, impregnated with antiseptics) to the finished supports. After a few days, you can begin building the walls.

If necessary, the tops of the piles are tied with a grillage. It is needed if it is to be built, block or

To make it easier to attach the grillage or the first crown of the log house, studs are inserted into the concrete before it hardens. After the solution has set, holes are drilled in the right places on the timber/log, and it is simply pushed onto these studs. There is another option - steel heads with a U-shaped plate are installed. But such fastenings are more expensive, and they do not differ in strength. Perhaps, install adjustable heads so that when certain piles settle, the difference can be corrected.

If you are planning to make the grillage out of iron, then you need to use steel pipes as formwork. In this case, it will be more convenient to install screw piles, but they are expensive, and it is also necessary to monitor the quality of their manufacture and painting. In this case, it is better to take galvanized ones - they last longer.

The distance between the finished piles is then filled with concrete or concrete/wood beams are installed and secured together. This is done to prevent wind from blowing under the floor.

Brick pillars

Piles/pillars for the foundation of a bathhouse can also be made of bricks or rubble stone, which are connected to each other using concrete mortar. Then the foundation is called columnar. The choice of location and distance between supports are similar. The manufacturing technique changes - bricks are placed on mortar.

In the corners they are placed with a square section (at least 38*38 cm), the intermediate ones are made rectangular 38*25 cm. To save on bricks (rubble stone), half the depth of the pit can be filled with coarse sand. Sand is poured into layers of 10-15 centimeters, each layer is filled with water and compacted thoroughly.

Brick piles/pillars are made 30-40 cm above the ground level. The space between them is then filled with brick (thickness - brick or half a brick). These brick walls need to be buried 25-30 cm into the ground. The piles and walls are leveled using mortar and covered with a layer of roofing felt to ensure waterproofing.

When starting construction and preparing a project for a future building, you first need to decide which foundation will best ensure the reliability and durability of the structure. One of the options for constructing the foundation of a building can be a foundation on bored piles, which combines not only high strength characteristics, but also the technological advantages of its arrangement.

An example of a foundation on bored piles

The ease of its construction and attractive price make it possible to use this type of foundation for buildings in private construction.

The main feature of this technology is reinforcement or bored piles located at the points of distribution of the total load-bearing load.
Technologically, the construction of bored foundations involves the installation of the following main elements.

Scheme of foundation construction on bored piles

Piles

For their device use:

metal or asbestos-cement pipes of various diameters;
reinforced frame using metal mesh and roofing felt.

It is advisable to drill holes for bored piles using a hand tool equipped with a special attachment that allows you to make holes of a wider diameter in the lower part of the well. The expansion of the lower part is necessary to better secure the support.

Grillage

This is the name given to the upper part of the foundation, which connects the bored supports and provides the same reinforcement as the supporting reinforcement.
The grillage can be of three types:

shallow belt;
suspended;
monolithic.

Depending on the type of future building and the area where it is located, the optimal option for constructing a connecting structure is selected.

An example of a grillage design for a bored foundation
The unity of these basic elements provides a reliable foundation for a building for any purpose.

The main advantages of foundations on bored piles

The technological construction of a foundation on bored piles has a number of undeniable advantages that make it possible to use it for almost any building and in any area. The only limitation is that it is impossible to make a bored foundation in rocky areas; in other conditions, its arrangement can be done even without the use of additional equipment.

Among the main advantages of this solution to the construction issue, the foundations of the building can be identified as follows.

These advantages make it possible to use this technology in the construction of various buildings for industrial and private purposes. The simplicity of the device and low overall cost make it especially attractive for the owner who plans to do the work with his own hands.

Calculation of the plan for a bored pile foundation

In order for the foundation on piles to be reliable and durable, it is necessary to calculate the number of supports to be installed, since they will take on the entire load-bearing load of the future building.

Drawing with dimensions and calculation plan for a bored foundation
To perform a correct calculation of a bored foundation, it is necessary to take into account and use the following data.

It should be noted that it requires maximum precision and care, since the reliability and durability of the future construction depends on this, so the best option would be to contact the appropriate specialists.

Technology of foundation construction on bored piles

Making a bored foundation with your own hands for a house, bathhouse or other outbuildings is not particularly difficult, since the technology for its construction is quite simple.
The entire construction of the foundation is divided into three main parts:

Knowing the step-by-step work plan, the time to build the foundation will take no more than 7-10 days.

Foundation marking

To mark the terrain you will need pegs and construction twine.

Starting from one corner, the pegs are sequentially installed at a given distance along the remaining corners of the future building, with the obligatory check of the equality of the diagonals of the resulting rectangle.

A marking twine is stretched over the driven stakes, which serves to mark the remaining stakes.

Based on the calculated distances along the twine line, internal points are set, which are also marked with stakes, and twine is stretched along the lines of the partition walls.

Instructions for marking the foundation

The area for the base of the building is leveled taking into account its general structure; in some cases, the top layer of turf is removed or a trench is laid for a grillage.

Installation of piles

The installation of a bored foundation is carried out in the following order.

Drilling holes for bored piles. The diameter of the hole is made 5-10 cm larger than the planned diameter of the support, and the lower part expands within 2 diameters to a height of 30-40 cm. The total depth should be at least 30 cm below the freezing point of the soil. The optimal value is considered at 50 cm.
Well preparation. It is necessary to compact well the base of the well, as well as the side surfaces, and fill the sand cushion to a height of 10-15 cm. For better contact with the cement mortar, the sand filling must be spilled with water and compacted again.
Preparation of piles.
The length of the supports should be such that their edges protrude no more than 10-15 cm above the ground level. The finished piles are placed in the prepared holes.
The production of reinforcing elements is carried out from corrugated metal rods with a diameter of 10-12 mm, while it is recommended to use 4 vertical rods with a horizontal tie of at least 30 cm for one well. The length of the vertical rods should be 10-15 cm greater than the length of the support.
The process of reinforcing foundation pillars

All elements are securely fastened together with knitting wire or welded to each other. The finished structure is installed in the center of each pile, excluding contact with its walls.
The process of placing reinforcement into holes
Filling with cement mortar is carried out simultaneously with vertical level control. After pouring the first 30 cm, the pile must be lifted and set back to better fix the base. Further filling is carried out with intermediate compaction. After the solution has set, the outer side of the supports is covered with pitch and soil and also compacted.

Further construction can be carried out no earlier than 3-4 days after pouring, when the cement mortar gains strength.
The video shows how to pour a foundation on bored piles with your own hands.

Construction of a connecting grillage

The procedure for constructing a grillage directly depends on the type of structure, but the general rules remain the same for all types. Let's consider the main technological stages on a shallow-depth strip grillage.

Preparing the trench. Along the entire perimeter of the future building, as well as along the lines of intermediate load-bearing walls, it is necessary to dig a trench 30-40 cm wide to a depth of 40-50 cm, the base and side surfaces of which are well compacted.
A sand cushion 30-40 cm high is poured along the entire length, which is spilled with water and compacted again.
Next, along the edges of the trench, it is necessary to install formwork, the height of which should be at least 20-40 cm at the highest point of its location. The material for, as a rule, is board panels fastened together.
To prevent displacement and changes in the configuration of the formwork during the pouring process, spacers are placed on the outside, and the parallel components are fixed together with bars.
An example of formwork for a foundation
When strengthening the grillage, welded or corrugated metal rods with a diameter of 8-10 mm are also used, while the edges of the horizontal rods are firmly connected to the reinforcement of the supporting elements into a single structure. The size of the vertical rods must correspond to the height of the planned foundation.
Filling with concrete should be done at once to prevent horizontal delamination. During the filling process, the solution is compacted either manually or with a special mixer.
When pouring large volumes, it is advisable to use factory-produced concrete or use a concrete mixer for its production in order to reduce the time and labor intensity of the process.
Upon completion of filling, it is necessary to check the horizontal level of the surface.
The process of pouring foundation formwork with concrete mortar

After the concrete has hardened, the pile foundation is ready for further construction, but not earlier than 7-10 days after completion of the work.
When arranging a grillage of another type, the differences will only be in the method of constructing the formwork and laying the reinforcing elements.

By following all the steps step by step, you can complete it yourself in the shortest possible time.

Thus, a foundation on bored piles is an almost ideal solution for or. Its simple technology allows you to do all the work yourself, while providing a combination of reliability and efficiency.

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