What is a pile foundation grillage. Pile-grillage foundation. Purpose and functions

Due to the high cost and complexity of installation on slopes, new type foundation - pile-grillage. Its peculiarity is that it is a combination of strip and column type foundations and it is used in the construction of buildings on slopes. For mountainous areas, this type of foundation is considered a priority, although it is quite expensive due to its design and design complexity.

What is the type of foundation

A grillage is a slab or beam that connects piles directly on the surface of the earth. This is actually the main bearing reinforced concrete belt, on which bearing walls the building itself. As a rule, when designing and calculating a grillage, detailed drawings of all elements are used, because the main load falls directly on the slabs themselves.

Accordingly, in any scheme of such a design, calculations of the allowable loads for each pile separately, as well as for the base slabs, are already provided. It should also be noted that the width strip base much larger than the walls. This is done in order to distribute the mass of the supporting structures of the building over the entire plane of the slabs and ensure good stability even with direct movements of a single support.

Where is grillage used?

During the construction of baths, technical buildings with a small mass of load-bearing structures;
During the construction of residential buildings on slopes with a large angle of inclination;
If it is necessary to make a garage or basement built into the depths;
When stratification is found during geodetic studies of the soil, especially when combining clay and sandy soil;
During the restoration of stone and concrete foundations buildings of an old construction, if subsidence of individual corners is found. Then special supports are brought under the base, then the platform is poured and only then the supporting grillage is carried along the outer part.

The choice of piles for the future foundation

As a rule, it is relatively difficult to make a pile-grillage foundation with your own hands, but it is technically possible. To do this, the type of piles is first selected, and they are reinforced concrete, concrete, metal and even wooden.

Today, it is possible to fill a pile grillage even with ready-made piles that are driven into the soil with pneumatic hammers, but this technology is expensive and is more often used in the construction of large industrial, administrative and residential buildings.

There are also so-called injection piles with a diameter of up to 120 mm and a single reinforcing bar, but they are used exclusively to strengthen and repair existing foundations.

The location of the piles in the grillage

Single pile - here each pile is located under its support, and all supports are connected into a single whole by reinforcement;
Ribbon connection. Uniform distribution of all piles is provided and their distance is indicated in the drawing;
The strip arrangement of piles is used in the construction of massive and large buildings;
The location of the bushes. A whole bunch of piles is installed in one place and takes on increased loads;
Field location. This is the case when a monolithic slab is poured over the piles, and all the piles are installed in a checkerboard pattern according to the scheme with clear calculations of the length of each unit.

Construction of a pile-grillage foundation

Determining the type of soil and its structure. Here it is desirable to obtain a geodetic section of the soil with detailed data for each soil layer. After all, piles are often driven to a depth of up to two meters;
Preparation of a pit or trench. It is desirable to do it on flat surfaces, on slopes it does not give any effectiveness. The optimal solution is the preparation of small depressions in which a sand cushion is made;
Formwork installation. It may or may not be done. If a private trader is ready to make a foundation with his own hands fixed formwork, then such a foundation will have excellent waterproofing characteristics;
Now you can carry out the process of deepening finished piles or pouring rebar concrete mix . Holes for piles are drilled with special equipment, then outer contours covered with ruberoid. Asbestos pipes are installed inside the wells, which are additionally reinforced to increase the strength of the supporting structure. After the full installation of the piles, the procedure for pouring the piles with concrete and creating an intermediate backfill begins;
After the piles have gained the specified strength, reinforcement of the frame is carried out along the entire horizontal perimeter. Reinforcement must be poured with concrete.

Errors in the design and installation of reinforced concrete grillage

The absence of a clear project with a detailed calculation of all the locations of the piles, their thickness, length, as well as a geodetic map of the territory.
There is no clear rigid connection between the pile columns and the bearing slab. If the soil begins to freeze in winter, then it expands. As a result, under the lower part of the insulated floor, the soil cools more slowly and a multidirectional force arises. This force tends to overturn the column, the frozen earth presses on the upper layers of the column, and the lower one takes the load on itself. As a result, the column begins to tilt, and if they are not fixed rigidly from above, then they will definitely be torn out of the grooves of the filled grillage.
An air cushion is not provided in the lower part of the grillage. If the bedding under the grillage is not removed, then through seasonal changes temperature, a significant force will act on it. Over time, it will lead to a rupture of the supporting platforms, damage to the grillage tape. To prevent this from happening, during pouring, polystyrene foam plates are laid at the bottom of the pit, which play the role of a shock absorber and protect the soil from freezing.
Incorrect calculation of the allowable depth of piling. If they are not clogged deep enough, then in this place the building will give a drawdown, there will be a distortion of the supporting structure and a collapse of one corner. Over time, the slab itself collapses through excessive loads and the basement of the building. Also, through incorrect calculations or the design of the grillage design, a sharp rise of one or more piles is possible, and this inevitably entails the destruction of the ceilings with the further destruction of the building itself.
Incorrect calculation of the bearing capacity of the foundation. This mistake can often be found in novice designers without work experience and practice. Here the problem lies in the wrong choice of soil type, because the whole calculation is based on this. Rocks and stony soils have the greatest bearing capacity, fine-grained sandy soils have the smallest. If you make a mistake in the calculations, there is a risk that the future building will constantly sink into the ground over time, and this process will be very difficult to stop. Therefore, a full-fledged layout, length and diameter of each pile is needed here.

A grillage is a structure that tape-tie piles during the construction of a pile-grillage foundation. It consists of slabs or beams laid on piles at a short distance from the soil surface. The foundation grillage can be made of logs, a metal profile: an I-beam, a channel or a corner, concrete beams or monolithic concrete. The foundation, the top of which is not made as a strip, but in the form of a common slab, can be the basis of an entire building. If during use there is a need to make a foundation for a local increased load, for example, for a massive column, then a pile arrangement of piles is used. On such a bush, the foundation is made in the form of a common slab for the bush, and not as a strip. This foundation is convenient on slopes, with variable terrain, on swampy and other moving soils.

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Simplified foundation calculation

It is important to correctly determine the number of posts required for a particular weight of the building and their location in the plan. The initial data will be the bearing capacity of the soil and the weight of the building. The bearing capacity of the soil is expressed in kg/cm² of soil. The weight of the building depends on the material used and the snow and wind load. From dividing the weight of the building by the bearing capacity of the soil, we get. To avoid miscalculations, we increase the resulting value by 30%, creating a margin of safety. To determine the number of pillars, divide the resulting foundation area by the area of \u200b\u200bthe support of one pillar.

Then follows the arrangement of the pillars in the plan. There are three principles to consider here:

pillars must be located in the corners of the building;
they should also be located at the intersection or junction of walls;
the distance between the pillars is planned from 2.5 to 3.5 m. If the distance is less than 2.5 m, costs will increase, if more than 3.5 m, there is a danger of the grillage breaking or cracking in it.

The top of the pile is embedded in a grillage up to 10 cm. The height of the remaining part of the grillage is determined by the resistance of the material to punching. After selection, a check is made. The grillage parameters must comply with the condition:

F/u+M/Wb< Rbt х Hp, где:

F is the concentrated force from an external load, for example, from a column (kg);

u is the area of force application (cm²);

M - moment of force relative to the axis of the pile in the plan (kg x cm);

Wb - static section modulus (cm³);

Rbt - ultimate total tensile strength of concrete and reinforcement (kg / cm²);

Hp - the height of the grillage (cm).

The edge of the grillage in the plan must be separated from the edge of the pile by at least 0.15 of the diameter of the pile or its side. This size must be at least 5 cm. The height of the grillage is determined by Hp = Ho + 0.25m. Where Ho is the design height of the grillage, which must be at least 0.3 m.

Piles used in a strip-grillage foundation can be made of various materials: concrete, metal, brick and even wood. Reinforcement of a concrete pile is carried out during its manufacture in a workshop or at the installation site for bored and bored piles. Much depends on the load. Technologically, piles can be divided into bored, screw, drilling, driving, vibro-submersible and pressed. Grills differ in the level of their location above the ground. A low grillage partially transfers the load from the building directly to the ground. A high grillage transfers the load to the ground through piles.

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Cast-in-situ concrete grillage and its reinforcement

Most often it is made of monolithic concrete. With this option, reinforcement is required. When constructing the foundation grillage, special attention should be paid to the spatial reinforcement cage. Typically, the grillage has a rectangular cross section and tape connects the piles to each other. During operation, compressive and bending loads occur. Formwork is used during construction. If for some reason it was not filmed upper layer soil, then only the side walls are made. After the concrete has hardened in the foundation body, the formwork is removed and the soil under the grillage is dug up to a depth of 0.2 m.

If the soil is removed, then the formwork is made with a lower bottom. The bottom must be removable. This bottom must be made of a board with a thickness of at least 40 cm. The inner surface of the formwork is made of planed boards.

The bottom of the formwork is reinforced with stiffening ribs from boards and additional supports.

If this is not done, then the formwork body may break under the weight of poured concrete. To avoid loss of cement milk, the formwork is lined with plastic wrap.

Has its own characteristics. The reinforcement frame must be located at a distance of three rod diameters from the outer surface of the foundation grillage. It is made in the form of two belts at the upper and lower edges of the grillage. In order for the reinforcement to be in the desired position and not move when the mortar is poured, the belts can be attached to horizontal rods inserted into the holes in the side walls of the formwork. Half an hour after pouring the formwork, the horizontal rods are removed.

In order for the reinforcement of the foundation to be reliable, thick metal reinforcement with a periodic cross section is used. Rebar welding is not recommended due to the appearance of unwanted stresses in the structures. The use of knitting is much more reliable. The grillage frame on piles can be reinforced with synthetic reinforcement, but only under small loads. The tensile strength of such reinforcement is higher than that of steel. Better adhesion to concrete. But according to the standards, it is not used in foundations and ceilings.

When pouring concrete, air cavities remain inside the solution. Therefore, the flooded foundation is processed by a vibrator. If there is no vibrator, then they do “pinning” - they slowly pierce the filled volume with reinforcement rods. Air pockets inside the grillage significantly reduce its strength. After laying, the concrete is covered with plastic wrap. After drying, the foundation should be poured again with water and covered with a film. These cycles are repeated for 7 days.

With a tape-built top, they require less concrete and reduce labor costs. The distance between the supports should be at least 2.5 m. With a smaller distance, the effect of saving concrete is small. No large volumes required earthworks. If piles are installed using special equipment, then excavation is not required at all.

The relatively small lateral surface of piles of a high grillage foundation reduces the level of vibration transmitted from the ground to the building. This is well felt when buildings are located near highways and railways. The pile foundation has a greater durability compared to other structures. Less time is required for the construction of grillage structures. The need for labor resources is decreasing. The disadvantages usually include the relative difficulty in equipping the basement.

For a long time I wanted to ask the question for a very popular topic.
We will accept that "piling" is a "piled grillage" distorted in the mind
Thanks to the book of Mr. Yakovlev and TISE, it has become customary to say that "de facto" - should be hanging. With it, everything is more or less clear, the air gap protects against heaving of the soil.
In the literature, there are 3 types of grillage.
1) recessed
2) not buried
3) hanging
Moreover, I did not find a more or less intelligible description of what is what and what it is used for.
With p3, everything is clear - there is a lot of information on the forum.
With p 1, not everything is clear, except that the grillage seems to be buried almost to the depth of freezing and is used in "large" construction. In general, this view is not very interesting.
But at the moment, I'm most interested in option 2. Since it is often called "pile tape" and is done by some builders.
Dear ALEX2626, in response to my statement, he described the following design - "pile strip foundation"
And what do you think to call it, filled with, if not pile-tape, and what does the inflamed brain of the builders have to do with it. Pile-tape (or pile-grillage) - exit in almost any soil, subject to the conditions, it turns out to be cheaper simply. For example, the most common type of shallow foundation - tape - 300 mm in the ground, 500 above the ground, width 400 mm - cross-sectional area \u003d 0.32 m2, multiplying by for 10 * 12 m - tape length 64 m, TOTAL FOUNDATION VOLUME \u003d 20.48 M3, at the same time it is necessary to put sand with crushed stone 300-400 mm under the tape, therefore dig to a depth of 600-700 mm, and this is 18 m3 of land work. Now we consider the pile-tape - we drill with a gas drill (or a hand drill with nozzles) to the freezing depth (in Samara 1.6 m) in one day 42 holes, put PGS 100 MM right on the ground and make a tape of 500 * 400 mm on it, volume foundation \u003d piles 3.3 m3 + tape 12.8 m3 \u003d 16.1 m3 - in total we get a foundation arranged according to all standards, i.e. to the freezing depth at a lower cost
That's how they often do it. on any soil motivating the fact that the pillars are below the freezing depth and that means everything is ok. I believe that such a design is safe only on non-rocky soils - for the following reason:
As water expands when it freezes, the volume of soil saturated with water increases. Roughly speaking, the earth, expanding, presses on the foundation from below.
If you just have posts, then they are affected by lateral grip with the ground and press from below - if the post is above the freezing depth.
In the case of "pile tape" according to the ALEX2626 version - adding 10 cm of ASG "right on the ground" the frost heaving force will not go anywhere. It turns out that when the soil freezes, the expanding soil will put pressure not only on the posts, but also on this "tape" and the fact that the posts are below the freezing level is not at all important here.
Since the tape is rigidly connected to the piles, this entire structure will begin to extrude. And the most unpleasant thing here is the following - when extruding, the piles will rise in their "wells" and a void will form between the bottom of the well and the bottom of the pile. Soil from the walls can easily crumble into this void, or a lot of other unpleasant things can happen.
As a result, the void will be filled, and in the spring, when the soil "leaves"
The pile may not get back into its place, and still remain "raised", and since it is rigidly connected to the "tape", it will warp the tape.
Accordingly, this is a direct path to potential problems with such a foundation on heaving soils.
I specifically highlighted the word potential - because this is one, but a probable path for the development of events. Moreover, this may not happen immediately, but let's say after 2 years or 5 years or 10. Or maybe it will "carry" ...
It’s just not clear why to play such roulette when you can do it differently
So I would like to understand - what is a "piled strip foundation" without an air gap and how much it has the right to live in heaving soils.
Note. al185. Topic summary

The design of pile-grillage foundations is much cheaper than popular strip foundations and gives excellent results in terms of reliability and durability. Wherein technological process so simple that it is possible to do all the work with your own hands.

Pile-grillage foundations in construction

Pile-grillage supporting structures for buildings and structures are increasingly replacing the popular tape ones. This is especially true for construction in areas Far North where they are the only possible option foundation devices for any building.

Building a foundation is a costly business. In the estimate of construction costs, this item is up to 45% of the total cost for the installation of the most popular supporting base of the tape structure.

The pile-grillage foundation is a monolithic structure (grillage) located on pile supports.

What is a pile-grillage foundation

The main feature of the pile-grillage foundation is the use of piles as the main bearing element. They are buried in the ground different ways until a reliable ground layer is reached, but in any case below the level of its maximum freezing.

To connect the pile system in the horizontal direction, horizontal beams made of various materials:

cast concrete. They are made simultaneously with pouring piles or separately. Such foundations can be used in the construction country houses up to two floors high;
wooden. Wooden grillages are used in the construction of log and lumber buildings, baths or outbuildings. They are also used in the construction of frame buildings and the installation of greenhouses in combination with screw metal piles;
metal from various profiles - beams, channels and corners large sizes. They are popular in the installation of non-residential buildings, such as workshops or garages.

The main purpose of the grillages, in addition to the horizontal strengthening of the supporting base, is the uniform distribution of the load from the structure located on it to the piles. This design prevents distortion of the building during operation.

Photo gallery: types of pile foundations

Pros and cons of grillage foundations

The positive qualities of grillage foundations include the following qualities:

Inherent design cons do not outweigh positive qualities listed above. The disadvantage is the fact that with such a foundation it is impossible to arrange a basement or underground. The second negative point is that to close the opening above the piles, you need to arrange a pick-up. But this is easily solved with inexpensive vinyl siding.

Video: the pros and cons of pile foundations

Scope of pile-grillage foundations

Pile foundations are used under unfavorable landscape or hydrogeological conditions for the construction of any objects from fences and outbuildings to residential buildings with a small number of storeys. It is economically beneficial to choose a strip foundation using bored piles in such cases:

A high grillage rises above the ground, the heaving force practically does not affect the foundation. The support is transferred through piles to the ground with high bearing capacity.
A pile foundation with a metal grillage from a channel is great solution for the construction of wooden buildings.
Bored piles with a monolithic concrete grillage cope well with the load from two-story brick and aerated concrete buildings.

Pile foundation with grillage

When designing foundations, the two main tasks are to ensure the bearing capacity and counteract the forces of swelling of the soil when it freezes. In other words, it is impossible to allow the structure to subside under its own weight and to skew it with uneven heaving. The main sustainability measures are:

Let's make a reservation that the pile-grillage foundation should not be confused with the tape, based on piles. The difference lies in the fact that the grillage rests only on piles at nodal points, while the tape is fully supported both on pile devices and on the ground.

There are three types of grillage by location:

High. Regardless of the method of manufacture and material, the grillage is located at a distance from the ground. Such structures are used in the construction of overpasses, bridges, residential buildings and outbuildings on slopes. A separate area of \u200b\u200bapplication is the construction of piers or piers.
Elevated. The sole of such a grillage is at ground level, not resting on the ground. The support device of this design allows you to keep the air cushion under the building, protecting it from the wind. The disadvantage is the lack of access to the space under the house.
Recessed grillage. A very common and popular design due to its low cost and functionality. The difference from others is that the tape is located below the ground level. The tape is poured into a grooved formwork.

Unlike a strip foundation, a pile-grillage foundation has supports only at nodal points.

Production of a pile-grillage foundation

It is quite possible to make a pile-grillage foundation with your own hands with minimal experience in performing construction work.

Piling manufacturing

The type of piles is selected based on the specific hydrogeological conditions at the site. Before construction begins, a preliminary exploration drilling at the site of the building. In the case of private suburban housing, this can be done independently using a small-diameter auger drill. The purpose of the study is to determine the nature of soils and the depth of the bearing layer.

We will consider the manufacture of a pile using the example of a bored support device. Work is carried out in the following order:

Types of standard piles

Several types of piles are used in construction. If we classify them according to the material of manufacture, the main ones are:

Concrete or reinforced concrete.
Metal from various profiles: beams, channels, pipes.
Wooden from a bar or round timber.
Plastic from the corresponding pipes.
Asbestos-cement.

In addition, piles are distinguished by the way they are immersed in the ground:

Driven - their immersion is carried out by hitting special hammers, vibrators or by pressing into the ground. Hammers and vibrators are used only at a distance from active objects or residential buildings, since ground shaking can cause it to move under these buildings.
Hollow shell piles - immersion is carried out by vibration method with simultaneous removal of soil from the internal cavity and its replacement with concrete.
Drilling - are arranged by drilling a well, followed by reinforcement and pouring concrete directly into the ground.
Stuffed - are made by the formation of a cavity by compressing the soil and pouring it with concrete.
Screw - are immersed by screwing into the ground using special mechanisms or manually, if we are talking about individual housing construction.

It is not possible to talk about the disadvantages or advantages of certain piles. These support elements are always selected on the basis of specific conditions. For example, you can't use cheap wooden piles in conditions of high soil moisture on the site, they will quickly fail. In places with acidic soils, metal piles should not be used, plastic or asbestos-cement piles are preferred.

Photo gallery: types of piles

Location of piles in the foundation

The number of piles for a particular building is determined by the weight of the building and the total area of the supporting surfaces. Data on the permissible specific load at the construction site can be found on the Internet or obtained from local construction organizations.

When planning the foundation, consider that:

The cross section of the foundation along the outer perimeter and for internal partitions should be the same.
Piles are installed at all intersections of the walls.
The distance between the axes of adjacent supports should not be more than three meters for individual housing construction.

The distance between piles may vary.

Placement of piles on the foundation plan

This operation must be performed according to the method described in the previous paragraph.

Drawing pile foundation represents the location of reference points with their binding to the axes of the reference base. On internal walls and partitions, it is also necessary to install supports, observing the distance between them.

Grilled foundations on piles are more difficult to perform than other types of supports. But they are less time-consuming and economically justified. When choosing such a design, the drawing should contain not only the layout of the piles, but also an indication of the assembly sequence and information about necessary materials to make a foundation.

The pile field plan should contain the layout of the piles, the dimensions and material of the grillage, as well as the necessary data on the sequence of assembly of the foundation elements

The decision on the nature of the arrangement of piles is made on the basis of an analysis of the nature of the soils and their bearing capacity.

Table: average calculated soil resistance

Priming	Design resistance, kgf / cm 2
Crushed stone, gravel	5
Sands are large, gravelly	4
Sands of medium size	3
The sands are fine and silty dense	2
Fine sands of medium density	1,5
Sandy loam hard and plastic	2,5
Loams are hard and plastic	1,5
Clay hard	4
Plastic clays	1,5

With such data, it is possible to calculate the loads on the foundation and its individual parts and design it in such a way that all its parts are loaded equally. Otherwise, there will be local stresses in the supporting base, which are not conducive to long-term operation.

Ways of arranging piles

Ways of arranging piles are as follows:

Tape method - all piles line up along the same axis. It is used to evenly distribute the load on piles with an equilibrium structure of the structure.
The cluster method - piles are concentrated in a certain area, which is subjected to increased loads due to the peculiarity of the execution of the upper structure. To equalize the loads in this place, several piles are made, combined with a monolithic grillage.
Pile field - arranged when it is impossible to use a simple strip foundation, as calculations show excessive loads on piles. A series of additional tapes is created, the axes of which intersect. United by a grillage, they take part of the loads on additional piles.

Depending on the design features of the building, one of the following is chosen for the construction of the foundation under it. three ways pile locations

The procedure for calculating the pile-grillage foundation

When performing foundation calculations, you need to calculate the mass of all parts of the building:

Self weight of piles and grillage, including mass of concrete. To do this, you need to approximately select the diameter of the piles and the cross section of the grillage. Then the volume of a single pile is calculated. For calculations, the formula is used: mass is equal to density times volume.
Own weight of the foundation. To do this, we multiply the cross-sectional area of the grillage by its total length and by the density of concrete and add it to the mass of all piles.
House frame weight. The principle is the same - determining the total area of walls and piers, excluding door and window openings, followed by multiplication by the thickness. Specific gravity various materials are easy to find on the Internet.
The total mass of the house, including ceilings and roofing. Produced according to the quantity of materials used on the basis of a draft design.
The total load on the ground, as the sum of all the results obtained in the previous stages.
Additional load from furniture and equipment. It can be taken equal to 150 kg for each square meter. The resulting value is added to the total mass of the house.

Next, you need to determine the area of \u200b\u200bthe supporting surface. For this area cross section multiply one pile by the total number of supports. Dividing the total mass of the house by the area of \u200b\u200bthe supporting surface, we obtain the specific load in tons per square meter.

Now you need to compare this indicator with the normative data for the soil at the construction site. If it significantly exceeds the recommended loads, proceed as follows:

increase the area of support by changing the bearing size of the piles;
increase the number of supports by reducing the distance between them;
revise the cross-sectional dimensions of the grillage in the direction of reduction;
once again analyze the design of the house, looking for the possibility of reducing its weight through the use of other, lighter materials.

For example, the total weight of the foundation and the upper structure of the house is 120 tons, the bearing surface area of the piles is 20,000 square centimeters. The verification calculation shows that the specific load is 120,000 kg: 20,000 cm 2 \u003d 6 kg / cm 2. The supporting soils for piles at the construction site are gravelly sands, the bearing capacity of which is 4 kg/cm 2 .

Conclusion: the number of piles must be increased by one and a half times (6: 4 = 1.5). As recommended above, it is possible to revise not the number, but the size of the piles.

Foundation pouring technology

The procedure for the construction of a pile-grillage foundation may look as follows.

Plot marking

In contrast to the marking of the strip foundation, the contour of the supporting base is not applied to the surface of the earth. The main operation is the installation of pegs at the location of each pile. The control operation is to check the equality of the length of the diagonals along the corner stakes of the outer perimeter and inside each rectangle of the inner partitions. Measurements must be made with a tape measure of the appropriate length.

It is necessary to drive pegs into the pile installation sites, and then check the equality of the diagonals along extreme points foundation

Earthworks and piling

Excavation along the contour with a high grillage is not carried out. It is only necessary to drill holes in the places where the stakes were previously installed. To do this, you can attract a contractor with a pit drill, then all work will be completed within a few hours. When using a drill with a diameter of up to 30 centimeters, the pits can be made by hand if the immersion depth does not exceed five meters.

The pouring of each pile must be carried out without interruption. For this, concrete grade 300 is used, which is constantly prepared at the work site. It is better to supply the solution into the well through a wooden or metal tray.

The work is carried out in the following order:

Vegetation is removed from the construction site, including grass, bushes and trees.
A well is being drilled.
If the depth of the well does not exceed five meters, it can be done with an ordinary garden drill
At the bottom of the well, a drainage layer of sand (up to 15 centimeters) and gravel of medium fraction (up to 20 centimeters) is arranged. The layer is compacted with a rammer and spilled with water.
Pipes of the selected material are installed in the wells. All upper ends of casings should be at the same level along the horizon.
Before pouring concrete, it is necessary to set the heads of the casing pipes to one level vertically
Reinforcing gratings are made and immersed in the pits, ensuring the release of the ends of the reinforcement above the pipe cut to connect the pile with the grillage when it is poured.
Concrete solution is prepared and poured into pipes. A break in the pouring of piles is allowed, but the formation of a pile must not be interrupted until the pipe is filled.
The pouring of one pile must be completed before the concrete inside the pipe hardens.

Be sure to seal it during the pouring process. Otherwise, voids may form in the body of the pile.

You can use the services of a concrete pump, then you need to prepare all the wells for pouring at the same time.

Grillage device, concrete pouring

It is possible to start pouring the grillage after at least 7 days after the completion of concreting the piles. Therefore, the time for preparatory work quite enough for the grillage.

At the end of the pouring of the piles, you need to proceed with the installation of the formwork for the grillage. It is made from any available material, but most often from boards. The shape of the formwork is a tray, fixed on weight with props. When installing it, it is necessary to control the horizontalness of the upper edge, otherwise an uneven supporting surface may result, which will inevitably affect the performance of the building.

Video: making a pile-grillage foundation

Pile-grillage foundations at one time became a revolutionary solution for the construction of a wide variety of buildings. The use of screw metal piles generally eliminates the need for excavation, which significantly reduces the labor intensity and terms of foundation construction. I wish you success!

In most cases, when the task of equipping basements is not set, best solution there will be a grillage foundation that has the ability to withstand a load greater than individual piles.

On stable, calm soils, it is placed for reasons of saving materials and time. Where there is a large freezing depth, heaving, weak soils, the construction of a foundation on piles with a grillage allows you to build not only light frame structures, but also large log cabins, brick or block houses.

Purpose and functions

Piles are optimal in areas with difficult terrain

When designing your own private house, you definitely need to figure out what a pile foundation with a monolithic grillage is, and whether it is suitable for this particular case.

Piles are used as load-bearing supports. the best option in difficult geological conditions, when heaving forces have a significant impact on underground structures, and a high level of freezing will require deepening of a monolithic tape over 2 m.

The diagram shows how the pile grillage design works:

The manufacturing technology differs from the usual installation of a building on piles in that all the supports are connected into a single base with a solid belt that receives and distributes loads on the columnar supports.

Types of grillage

The grillage connects the piles to each other

The design calculation, based on the conditions of the site and the total weight of the building, chooses which type of pile-grillage foundation it is advisable to use.

The decision is influenced by the need to install a ventilated underground under the crown, the possibility of flooding by flood waters, the slope (relief) of the site.

Based on these conditions, determine the height of the pile foundation grillage:

A low grillage has the advantages of a strip foundation

A low grillage is a combination of an unburied strip foundation with piles, which significantly increases the reliability, rigidity, and stability of the entire supporting structure.

This option combines the advantages of pile and strip foundations, while the combination significantly compensates for the disadvantages that appear separately:

the weight load of the building is transferred to the foundation concrete strip and, due to the presence of a reinforcing frame, is redistributed to the entire support area;
a monolithic low tape rests with its lower part between piles on a pillow (soil), providing a contact area with a support along the entire perimeter;
in winter, the impact of forces near the surface is compensated by buried piles.

Elevated grillages are used on difficult unstable soils

Level Up ground water the height of the concrete grillage relative to the soil surface increases.

The increased type is used on quicksand, peat bogs, karst, forest, fertile soils, more than 1.4 m thick.

This arrangement eliminates the effect of lateral forces on the monolithic grillage, and the piles are not only supports, but also an anchor in moving rocks.

The arrangement of such a foundation reduces the volume of earthworks, requires fewer materials and cash costs than concrete tape or slab. During installation, a monolithic reinforced concrete grillage will require precise observance of the design dimensions and work technology.

Material

wooden beam- cheapest material

The basis for the grillage under the pile foundation is selected raw materials that, according to their characteristics, can withstand constant and variable loads for a long time, which are included in the design calculation of the house.

A durable grillage on piles is made from the following materials:

steel profiles (channel, I-beam);
wooden beam (rounded log);
concrete (reinforced concrete) casting.

A low pile-buried foundation can only be with a concrete grillage.

Concrete structures are used for heavy houses

Metal grillages are made high, since, with their great strength, they need protection from moisture.

The reinforced concrete type, which rises above the ground, is used in the construction of fairly heavy houses, since concreting at a height will require good formwork.

Another criterion is the service life of building wall materials. The selected grillage foundation must meet or exceed the performance of the structures located above it.

How to support a pile foundation with a grillage from different materials on piles is shown in the diagram:

Pile selection

It should be considered what a foundation grillage device is from different types of piles. For such structures, any type of support can be used, based on the characteristics of the geology of the site and the total weight of the materials and internal equipment of the house.

The cross section (width), raw material, method of installation to the depth of the stable stop must correspond to the calculated load.

In private construction with their own hands, the use of bored piles, which are made by pouring cement mortar into the formwork. It is practiced to install asbestos-cement pipes, reinforced depending on Ø 4 - 6 vertical rods.

The load of such metal-reinforced supports can be significant and depends on the bearing capacity of the natural base:

Screw models are used for lighter buildings

When erecting light buildings (a bathhouse, a barn, a one-story cottage), a bored-type grillage foundation does not require complex calculations, it is important right choice support points.

Driven piles are installed using special mechanisms without drilling and earthworks. They are used in the construction of large multi-storey buildings.

Screw models are screwed to the desired depth and cut to the set level. They are available in lengths from 2 to 11 m. different types screw, so on large slopes of the surface it is possible to maintain the required dimensions of the grillage using various models products.

General rules

When choosing a pile grillage foundation, it is quite simple to take into account the pros and cons. The disadvantages include:

the need for special equipment if it is necessary to install heavy modifications, driving models;
requirements for anti-corrosion protection for steel products, antiseptic - for wood;
lack of underground facilities near the house. Recommendations of experts on the device of this type of foundation, see this video:

The design size of the grillage in width should be slightly larger than the supported wall, beam, crown.

According to SNiP, the step for piles in a strip grillage, including a stuffed foundation, is at least 3 Ø of a support. In this case, the chosen distance can also be 5 Ø, if the strength that the grillage foundation has in cross section allows.