One-story industrial building. Calculation of the foundation for bond block clones

Many homeowners often face the problem of building an extension to their house. It becomes necessary if you want to expand your living space by adding additional rooms. The construction of a foundation for an extension to a house has its own characteristics, in contrast to the technology for new construction. Here we need to find a way to dock it with the old base so that it is secure.

Foundation for an extension to the main house

How to tie the foundation of an extension?

We choose the method in which we will connect the old base and the new one.

There are two main pairing methods:

I. The first is the technology of rigid, reinforced connection

. It can be used if the foundation of the house building is stable, and by the time the extension is erected, its settlement has already occurred.

Calculation of the new foundation showed that its “hanging” on the old foundation will not cause additional settlement of the house above critical values. In general, rigid joining of foundations is reliable in non-heaving soils. In other cases it is not advisable.

The technology for making such a connection is as follows:

• We determine the type of old foundation (ribbon or columnar)
  , depth and dimensions. By digging a hole along the base wall, we determine the first two parameters. To determine its width, take a metal rod with an end bent at 90 degrees. We push (hammer, if necessary) it under the base so that the hook is in a horizontal plane. Then we turn it into a vertical position, and pull it up so that it rests against the back wall of the foundation, and we make a notch on the visible part of the rod in the place where the outer wall of our foundation ends. Carrying out the steps in reverse order, remove the rod. We measure the resulting distance.
• Different foundation designs react differently to soil heaving
  . Therefore, if the main foundation is, for example, strip, then the new one must be made as strip, despite the fact that foam blocks are a fairly light wall material.
• The depth of laying a new foundation should not be greater than the depth of laying the main one
  .
• Holes are drilled in the old foundation
  , the diameter of which will be slightly larger than the diameter of the reinforcement.
• The drilling depth is equal to the diameter of the driven reinforcement, multiplied by 35
  . The working length of the reinforcement is equal to twice the drilling depth.
• If the width of the foundation is not sufficient, then the reinforcement is hammered in
  (by half the width of the base), like an anchor, after first making a longitudinal slot at its end and inserting a wedging liner. The reinforcement will be securely fixed inside the foundation.
• Determine the required number of reinforcement bars
  . For a closed loop (node ​​3) of a new foundation: at the rate of five rods per quarter of 1 m2 of base wall. Using an emery machine or grinder, cut the required number of reinforcement rods. For an open (node ​​1 and node 2) foundation contour - depending on the width of the designed base.
• We hammer the rods into the drilled holes
  . We weld small washers to the ends of the reinforcement.
• Further, during concrete work
  , the visible part of the reinforcement will be monolid in the body of the new foundation.

II. The second method of pairing foundations

– arrangement of expansion joint. This connection option is more economical and easier to implement than the first.

The technology for connecting two buildings is as follows:

• An independent foundation is being built near the main building
  . An extension to a house does not require a reinforced foundation, as with all house construction, but you should consult a specialist for advice. No one has canceled the reliability calculations of the foundation.
• The gap between the bases should be 5 cm
  . To get it, before pouring the foundation, we lay boards wrapped in plastic film or roofing felt. You don’t have to take them out later, just leave them there.
• In case of very heaving soils, the floor of the extension is made slightly lower than the floor of the house
  - by the amount of expected deformation.
• If the expansion joint connects buildings no higher than two floors
  , then the distance between the walls can be 2 cm.
• The gap between the walls and bases is filled with insulation
  . Once upon a time tow was used, now there are many modern materials. This includes polyethylene foam, mineral wool, etc. The gap is then sealed with flexible, weather-resistant sealants. The junction is covered with decorative overlays, which are attached to one wall. As a rule, this is the wall of a permanent building.

Do-it-yourself foundation for a house extension

We discussed the technology for constructing foundations above. What needs to be done before starting this work?

If we want to carry out all the work ourselves, then we need to start with a consultation with a specialist. He will help you choose the optimal type of foundation and calculate its reliability. Next, you need to plan the site. How to mark the foundation of an extension?

• Using a cord stretched over pegs, we determine the geometry of the future foundation. We calculate the diagonal of the site using the formula: c=√(a²+b²), where a and b are the sides, and c is its diagonal.
• We measure a rope with a length equal to c, and with its help we check the equality of the site along the diagonals. If necessary, adjust the contour of the cord.
• If the foundation is not piled, then in the same order we mark the inner side, retreating deeper into the required width.
• If the perimeter of the foundation has a complex contour, then it is divided into rectangles, and the marking of each of them is carried out in the usual manner.
• Next comes excavation work.

As we can see, the main thing in building an extension to a house is to choose the right foundation design and correctly perform the mating of the foundations.

Given the same initial data, the cost of an extension with a rigid joining of foundations will be noticeably higher than when connecting with an expansion joint. But in any case, this process requires a responsible approach. The older the building, the higher it is.

Interesting video

• How to connect two foundations with your own hands? What is important to know?

1.2.2. Snow load

The full standard value of the snow load on the horizontal projection of the coating qсн. should be determined by the formula:

Concentrated load on the truss nodes: = 3.54 t where S0 is the standard value of the weight of snow cover per 1 m2 of horizontal surface of the earth, accepted in accordance with SNiP 2.01.07 - 85 for a given snow area S0 = 0.07;

B – frame pitch, m;

gf – load reliability factor.

m=1 – coefficient of transition from the weight of the snow cover of the ground to the snow load on the cover, adopted in accordance with SNiP 2.01.07 – 85.

How to connect two foundations with your own hands?

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What is important to know?

Owners of country houses are often faced with the issue of expanding their living space. If the initial budget did not allow for the construction of a large house with sufficient space, then it is possible to build an extension to the house.

Scheme of the foundation for the extension.

At the very beginning of construction work, the new foundation of the extension should be connected to the old one.

Before connecting two foundations with your own hands, you must keep in mind that a new foundation, even one made identical to the old one, will give rise to sediment. To prevent the formation of cracks on the walls, a sedimentary joint should be left between the walls. Attaching a new foundation to a house is possible in the shape of the letter P. If you drive piles into the old foundation. to connect it with a new one, the latter will still be subject to precipitation. If the procedure is carried out incorrectly, the facade will be torn. In this case, the assistance of a designer who can cope with this task professionally plays a special role.

Construction of a foundation for an extension to a house (scheme of connecting two foundations).

To properly build a foundation with your own hands, you should know the type and method of constructing it under the house. With the tape type, you need to know the size of the width of the base. If the old foundation is columnar, then construction is based on knowledge of the overall dimensions of the pillars and the depth of the foundation. According to experts, you should not combine the old with another type of new foundation of the house; they should be the same. You should not save on construction by choosing a cheaper type than the old one, since the shrinkage of different foundations is different. To measure the width, take a metal rod and bend it at a right angle; measuring the depth is easy.

In the process of connecting the foundations of buildings, it is important to take into account that in spring there is a process of decreasing the bearing capacity of the soil, which entails an increase in its humidity and additional shrinkage. The weight of the old and new buildings is different, so a technological gap is provided between them to connect the foundations. It is a gap ranging in size from 20 to 40 cm. Sections of protruding reinforcing bars are placed in it.

It is necessary to understand what type of foundation is best to pour in order to build an extension module to the house. During the connection process, the following tools and materials may be needed:

Connecting foundations using an expansion joint (diagram).

In order to expand the foundation, use a concrete solution or use reinforced concrete. If it is necessary to qualitatively connect two parts - old and new, in order to form a monolithic structure, the foundations are strengthened.

This type of work is carried out before pouring the base with concrete. During the strengthening process, the reinforcement of the parts that make up the foundation is welded. or reinforcement bars must be drilled into the old base.

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The main stages of connecting foundations

The steps that are performed sequentially when connecting two foundations are as follows:

Options for connecting the foundations of the extension according to the diagram of open (a, b, c, d) and closed (e) contours: 1 – existing house; 2 - extension.

1. Equipment of a trench for a new foundation at the same level compared to the level of the foundation of a new house. The ditch should be dug in parts, and not along the entire length, otherwise the soil will be exposed, which will lead to deformation of the existing concrete foundations.
2. An old building can be strengthened using inclined supports, and the old foundation of a house can be strengthened using reinforcement. To do this, it is necessary to drill several special holes into which metal products are secured. Roofing felt or roofing felt is laid between the foundation being constructed and the new one.
3. If it is necessary to change the depth of the foundation. special ledges are arranged, with a height not exceeding 50 cm. The construction of the first ledge is carried out while maintaining a distance of about 1 m from the foundation that already exists. Then work is carried out to equip a trench with a depth equal to the base.
4. Next, you should level the new ditch and clean it of stones, earth and other impurities. This is done for subsequent connection of the foundations at the same level. After this, the formwork is prepared, which is knocked down using wooden boards of dimensions corresponding to the height and width of the future foundation of the structure.
5. Having installed the formwork, compact the crushed stone prepared for the existing foundation of the trench and fill the base with concrete. The construction of a foundation that includes two layers of concrete is more profitable. The top layer of concrete will be more rigid, and the bottom will be more plastic. Concrete layers are poured with maximum density so that there are no gaps at the junction of two foundations. In this case, the subsidence of the base will decrease.
6. After the concrete has thoroughly hardened, the formwork is removed. Before starting the construction of the extension, the foundation must be allowed to stand.

The connection of two foundations can be carried out based on one of two decisions:

Scheme of a rigid connection between the base of the house and the extension.

1. Separately build an extension and connect the new foundation with the old one.
2. Rigidly combine the new foundation with the foundation of a residential building.

The choice of one solution or another is related to the severity of the attached structure and the condition of the soil on the site. If the soil is uniform, the house will not shrink, otherwise the construction of a separate foundation connected to the previous one will come into contact with the old one, overcoming the presence of an expansion joint.

Carrying out a full-fledged rigid connection of bases in order to create a single structure is a rather labor-intensive process.

If it is possible to predict the settlement of a new foundation in the presence of non-heaving or slightly heaving soil, then a rigid connection is most acceptable. It is also suitable when it is planned to build an extension to a house with two or more floors under one roof, so that the end result is one structure.

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The adjacent support structure foundation was moved to the bottom of the column

The compaction of urban and industrial development, the construction of new buildings near existing ones, especially within areas with soft soils, is a complex problem of foundation construction, since the structures of old houses as a result of construction activities in adjacent areas always receive damage, sometimes having emergency consequences. In St. Petersburg (Leningrad) alone, over the past 20 years, at least 70 buildings in the situation under consideration have received dangerous damage.

Damage to existing homes will not be tolerated. Therefore, it took considerable efforts of prospectors, designers, construction technologists, specialists in the field of construction machines, and researchers to significantly improve the situation. However, even today the problem is still far from being completely resolved.

“Deep” (conventionally) are called pits that need to be dug deeper than the base of the foundations of neighboring buildings.

Rice. 1. Results of field observations of the development of settlement of four residential buildings on Tverskaya Street. in St. Petersburg: under construction (No. 2) and existing neighboring ones (No. 1, 3. 4): a - plan (dotted line - dismantled two-story building); b - diagrams of settlement of external walls of buildings; c - movements of deformation marks indicated on the plan (double line - completion of construction)

Reasons for the development of additional settlements of buildings during the construction of buildings and structures near them

With the compaction of urban and industrial buildings, existing buildings receive settlement, which is usually called “additional” (sad). This precipitation (as opposed to “intrinsic” precipitation) occurs as a result of three main reasons:

1) construction and technological impacts on the foundation soil of an existing building - additional construction and technological settlement (sajl);

2) changes in the stress state of the base of an existing building when the soil mass is loaded with a new building - additional compaction settlement (sa(A);

3) the impact of technological equipment located in a new building on the foundations of neighboring buildings - additional operational settlement (sJ.

Additional settlement from construction and technological impacts (sm/i) is especially dangerous because it is always uneven and can reach unacceptable values ​​(Fig. 2). In addition, technological impacts can cause building failure.

The most significant reasons for the development of sajl are:

a) vibrations of the soil, foundations and ground structures as a result of driving piles and sheet piles with hammers or vibrators;

b) excavation of a construction pit deeper than the base of existing foundations;

c) freezing and thawing of the soil under the foundations of buildings during winter work in a neighboring pit;

d) quicksand liquefaction of the soil under the foundations during open pumping of water entering the pit;

e) deviation of the sheet pile walls of the pit, if there are old houses near it.

Precipitation sadl and loss of stability of the soil of the foundation of neighboring houses are especially dangerous when new structures are erected in deep pits. It is impossible to take into account the influence of the listed causes when calculating s, therefore it is necessary to ensure that sadl do not develop dangerously. This is achieved by selecting technologies and mechanisms for constructing or driving piles, excavating soil and other types of work in construction pits. This task is incomparably more difficult than a similar one carried out on sites free of old buildings and structures.

Additional settlement from changes in the stressed state of the foundations of neighboring buildings occurs because a “sedimentation funnel” is formed around the building under construction, the dimensions of which in plan are commensurate with the thickness of the compressible zone of the foundation (up to 20...30 m or more). The greatest precipitation occurs within the nearest 10 m from the area where the foundation is loaded with a new building (Fig. 3).

If a building is located within the sedimentary funnel, then it receives additional settlement. It follows from the theory that the sadi settlement is obviously uneven. The sensitivity of an old building to the development of gardens varies and depends on many reasons, which are quite difficult to take into account.

Modern numerical methods for calculating foundations by deformation, based on the theory of elasticity, make it possible to calculate the settlement of the base of the designed building and the additional settlement of buildings adjacent to it. Calculation of additional compaction settlement sads, in principle, is quite reliable, therefore it is an important stage in the development of such projects.

Additional settlements from production and technological impacts during the operation of equipment located in new buildings (structures) can cause additional settlement of the foundations of neighboring buildings, roads and communications. The most dangerous vibration impacts on the ground are during the operation of massive hammers, presses, powerful compressors and other mechanisms that generate low-frequency vibrations comparable to the natural frequencies of building structures. In such cases, it is necessary to use vibration protection equipment. Aggressive wastewater from chemical production is also dangerous due to the impact on the soil and foundations of neighboring buildings.

Design of foundations near existing buildings

The specificity of foundation projects located near existing buildings and structures is that they must ensure the normal operation of the structures of the new building and not lead to the development of deformations of the foundations of neighboring ones. The development of such projects and their implementation in production are quite complex and responsible.

When developing foundation designs for a new structure, possible settlement of neighboring buildings should be taken into account:

where s is the additional settlement determined by calculation, for example, by the corner point method; saJsu—maximum permissible value of additional draft.

By the time the extensions were erected, the old buildings had acquired their “own settlement”, which had been developing for decades. The average settlement of houses in St. Petersburg, for example, reaches 20...30 cm and greater values, i.e., exceeds the permissible values, which leads to the development of building deflection. If such a building receives additional settlement of the saJs compaction, then this leads to the development of arching, distortion, the configuration of the frame of the existing building changes, and cracks appear in the masonry of the walls. Shifts of floors, development of other defects and even collapse of structures are possible. The type of deformation of a building due to additional settlement differs significantly from the type of deformation caused by its own settlement. In this case, the use of average settlement, deflection, etc. when designing is unlawful. The study of this issue led to the need to introduce a criterion characterizing the influence of suds - permissible additional draft, namely:

- the maximum value of additional settlement, which, obviously, is received by sections of the walls of the old building that are closest to the new one;

— additional distortion of the new building in the adjoining area.

The permissible values ​​of the listed characteristics of additional settlement can be determined by a “joint calculation” of the old building with the foundation receiving additional settlement (for this purpose, numerical calculation methods can be used). In relatively simple cases, it is recommended to use the following conditions:

The values ​​of the maximum permissible values ​​for additional settlements of buildings of various types, which received different degrees of wear before the construction of the neighboring (designed) building began, can be determined from Table. 13.1, developed at St. Petersburg State University of Civil Engineering based on a generalization of the results of field observations of a large number of buildings near which new houses were built.

Justification of the design solution for the foundations of a new building attached to existing ones is the most important stage in the development of the project. In this case, the reliability of the initial information (about the engineering and geological conditions of the site, ground structures and dimensions of the building, loads for cutting foundations, etc.) and additional information about the location of neighboring buildings and existing communications, types of foundations of these buildings, information about the technical condition is of particular importance foundations and other structures. Typically, at such sites, preliminary inspections of the structures of buildings surrounding the site are carried out, with the recording of existing old defects.

Rice. 3. Schemes for determining the skew and tilt of the building as a result of the development of additional compaction settlement : a - skew of the building; b - tilt of a narrow building; c - the greatest additional draft of the point closest to the abutment line; d - shape of the sedimentary funnel: I - existing building; 2 - building under construction; 3 - diagram of the settlement of building 2; 4 - diagram of additional settlement of building 2; 5—precipitation contours

Values ​​of maximum permissible values ​​for additional settlements of structures and buildings of various types and degrees of wear of building structures

Table 1. Assessment of the technical condition of structures of brick, large-block and large-panel houses based on the results of surveys, taking into account the development of damage and physical wear

When developing development densification projects, it is recommended to adhere to a certain logical scheme. Foundation options are considered and the optimal one is selected to ensure that the conditions are met. The condition is checked and, depending on whether it is met or not, a number of options are analyzed to ensure the safety of neighboring houses and structures.

Option 1 - foundations on a natural foundation for the designed building. Additional settlements of the foundations of a neighboring building are calculated at several points. It is recommended to assign these points on the longitudinal adjacent walls at the following distances from the abutment line: 0; 1; 2; 4; 8; 16; 24 m. Based on these data, the values ​​smlmax, (.i/, - sm/2) / L determined by calculation are established.

If the condition is satisfied (which rarely happens, as a rule, only when the designed building is lower, that is, lighter than the neighboring one), the usual design of the foundations of a new building is carried out. If the condition is not satisfied, they look for another, more reliable solution, using other foundation options for the new building, the use of which can reduce the impact of the new building on the existing one to acceptable values.

Option 2 - cantilever connection;

Option 3 - disconnecting structures;

Option 4 - pile foundations for a new building;

Option 5 - strengthening the foundations of neighboring houses.

As a result, the design and technological solution for the foundations of a building is determined by economic considerations, the technological capabilities of the contractor, the permissible duration of construction and other factors.

Measures to reduce the impact of the new building on neighboring

Fundamentally, reducing the impact can be achieved through planning, architectural, constructive, technological and organizational measures. The planning, architectural solution or organizational and construction measures do not always depend on the designer, so we will consider them only in a condensed form.

Planning measures are aimed at ensuring that the new building is located at a safe distance from the existing ones - usually 10...20 m. Then the new building can be considered as “detached” and no specific problems with the foundations arise.

An architectural solution can simplify the task if the new building in the adjacent area is lightened in one way or another. Let’s say that in the adjoining zone there is a block whose height is less than the neighboring one, the new building is facilitated by passages, etc.

Constructive measures may include the following:

1) a new building is built on shallow foundations, despite the fact that the condition is not satisfied;

2) a new building is erected on pile foundations;

3) the construction of a deep underground volume (garage, warehouse, etc.) is planned under the new building.

The first constructive measure is used together with technological solutions that have proven themselves in practice: cantilever abutment, disconnecting sheet pile row, preventive strengthening of the foundations of neighboring houses with their transfer to reinforcement piles, consolidation of the load-bearing layer soil. In general, this group of measures can be considered as palliative (forced), since it is very problematic to guarantee the safety of neighboring houses during any extensions.

Cantilever connection .
The main idea of ​​this event is that in the junction zone the foundations of the new and old buildings receive a gap, the size of which is selected according to calculation so that the condition is met (Fig. 4). In this case, the walls, columns, and other structures of the new building rest on consoles, the projection of which is determined by the size of the “gap” determined by calculating the value of sud. According to the projects implemented in St. Petersburg, the overhang of the consoles was in the range from 2 to 5 m (for houses of 6 ... 12 floors), which did not create any special design difficulties. This event is effective if two conditions are met:

1) an air gap must be provided between the lower edge of the console and the ground, the size of which is set to be no less than twice the expected settlement of the new building;

2) between the foundations and walls of the new and existing buildings, a sedimentary joint must be made that works accurately. Special attention must be paid to the design of the seam and its execution.

Rice. 4. Schemes of solutions for cantilever connections of new buildings to neighboring existing ones implemented in St. Petersburg: 1 - foundation of an old building: 2 - beam with cantilever; 3 - foundation of a new building; 4 - column resting on the beam console; 5 - wall of a new building; 6 - gap between the beam and the ground; 7 - disconnecting tongue; 8 - foundation of a dismantled building: 9 - gap between the old building and the console; 10 - indentation pile; 11 - drilling pile

Disconnection structures in the ground. Their purpose is to change the stressed state of the soil so that the stresses at the base of the old building from the influence of the new one do not develop dangerously, and the additional settlement caused by them does not have dangerous consequences or is zero.

Such disconnecting structures can be formed:

1) metal sheet pile row;

2) a wall of secant or touching bored piles;

3) a slot in the ground filled with antifriction material.

Disconnecting sheet pile row. It was first proposed by B.I. Dalmatov. in the project of several 12-story buildings with one-story extensions (Dalmatov B.I., Sotnikov S.N., 1965). The sheet pile is immersed along the abutment line before digging a pit for a new building; the length of the sheet pile is determined based on cutting through the entire thickness of soft soils. Obviously, the sheet pile must be stationary, and this is achieved by the fact that its lower end rests on low-compressible soils (Fig. 5). In plan, the tongue and groove is located along the line of abutment of the houses and should protrude beyond their boundaries, forming “spurs” that can go around the old or new buildings in a section with a length of approximately 1/2 ... 1/4 of the thickness of the compressible zone of the base of the new building (see Fig. 4). As studies by S.N. Sotnikov have shown. and Levkina A.L. (1987; 1998), tongue and groove also changes the stress state of the foundation of a new house, ensuring a more uniform development of its settlement.

Rice. 5. Application of a disconnecting sheet pile: a - diagram for determining the length of a disconnecting sheet pile row (ht - size of the soil compaction zone: hg, - thickness of the underlying soil in which the friction forces supporting the sheet pile develop): b - location of the disconnecting sheet pile with different plan the form of junction of the new and old buildings; c - foundation with a cantilever beam covering the sheet pile: 1 - existing foundation: 2 - designed foundation (new building); 3 - sheet pile row: 4 - sedimentary seam

The effectiveness of the tongue can be increased if its surfaces are coated with anti-friction coatings. The most effective in terms of material consumption and technological impact on existing houses is flat tongue and groove, the consumption of which can be relatively small.

The use of sheet piles is limited by two factors: the danger of vibration during immersion, from which the foundations of old houses can receive additional precipitation, and the large depth of the roof of dense soils, since immersion of a sheet pile longer than 20 m is difficult. It is dangerous to use sheet piles where water-saturated sands and other soils with thixotropic properties occur. Modern hydraulically driven high-frequency vibrators are practically safe, therefore, the disconnecting tongue can be widely used in the future.

Disconnecting row of drilled piles. It was proposed by B.I. Dalmatov. and Bronin V.N. in 1993 and used with positive effect on several sites. This disconnecting structure has disadvantages: it is material-intensive, time-consuming to manufacture and can pose a danger to old foundations due to vibration, “release” of soil into boreholes and other influences. However, its use does not require the consumption of metal: the piles do not need to be reinforced.

A slot filled with anti-friction material. The slot is a promising and, apparently, relatively cheap design (Sotnikov S.N., Azis L., 1993). Its main idea is that a narrow excavation in the ground filled with a bentonite suspension - a material with minimal internal friction - prevents the development of additional foundation settlements from the influence of loading of the neighboring site. The theoretical foundations of this method have been developed in sufficient detail, but the design has not yet been used in practice.

Pile foundations for new buildings

They should be considered as the main and most effective measure, since this solution provides a completely reliable (settlement-free) foundation for a new building and, as a consequence, minimal settlement of existing neighboring ones. The main problem with this solution is the technology of making piles. Several types of piles are used:

a) piles of complete factory readiness (reinforced concrete, metal, wood). Depending on the method of immersion, they are divided into driven, immersed with vibrators, indentation, and screwing.

Piles of the first two immersion technologies are, as a rule, inapplicable, since vibration effects on the soil and structures of old houses and communications can lead to emergency consequences.

Indentation piles are largely devoid of these disadvantages. However, they have a limited load-bearing capacity, determined by the magnitude of the indentation force that the mechanisms develop (usually it does not exceed 600...800 kN). The material of such a pile does not always work effectively; the piles cannot be immersed in sufficiently dense soil, therefore both the new building and those adjacent to it receive settlement, although significantly less than with shallow foundations. The main disadvantage of this technology is that piles driven into the ground close to existing foundations cause additional settlement during the pressing process and after its completion. The existing experience is not yet sufficient to reliably determine the size of the safe removal of an indented pile from the old foundation or to name the types of soils in which these piles are safe. Perhaps the additional settlement of the existing building is due to a change in the stressed state of the soil when the piles are pressed in and its crushing (disturbance of the natural structure).

Screw piles are usually made of metal; they are driven using mechanisms that only specialized companies have. There is not yet sufficient experience in using these piles in the situations under consideration;

b) piles made in boreholes. These piles have numerous modifications depending on the method of drilling wells, securing the shaft, geometric dimensions, the composition of the concrete used, etc. The main differences relate to the method of drilling wells and extracting soil, including methods with flushing with water, clay solution, and casing wells with pipes.

Drilling wells with flushing is carried out with a drilling tool that is lowered into the well on a pipe. Water or a clay solution (an aqueous suspension of bentonite) circulates in the pipe and in the well, which removes destroyed rock (sludge) from the well. Upon reaching the design mark, a concrete pipe is lowered into the well. A plastic concrete mixture is fed through it, which displaces the suspension, and then the reinforcement cage is lowered into the concrete. The use of this technology is sometimes dangerous, since the well is not secured, soil spills are possible (especially when using low-quality clay), including from under the foundations of old houses, which is fraught with dangerous consequences.

Making piles by drilling wells with casing is the most common method. Existing machines can make piles with a diameter of up to 2 m. When building houses in cramped conditions, the most commonly used piles are 350, 400, 600 mm in diameter, up to 30 m in length, the bearing capacity of which can reach 3000 kN or more. At the same time, it cannot be considered that all technological issues of constructing drilled piles have been resolved, since there have been cases of damage to neighboring houses during the period of work. Strict technological regulations are required to ensure safe work in cramped conditions. The final stage of this type of work is filling the wells with concrete mixture (using a vertically moving concrete pipe) and installing a reinforcement frame.

Making piles using the “through” auger method appears to be the safest technology for adjacent old foundations. Its essence is that the auger blade, welded to a pipe of sufficiently large diameter, is screwed to the design depth continuously without excavating the soil.

Then the concrete mixture is fed into a pipe equipped with a loose tip using a concrete pump, and the auger with soil is gradually removed to the surface. In this case, the soil is replaced with concrete. This technology appears to allow for safe work around old foundations;

c) piles made in a cavity formed by ramming - squeezing out soil. This method is very effective in soft soil conditions, since the soil below the tip of the piles is not removed, but compacted. Such cavities can be formed using various technologies and machines, for example ATLAS and FUNDEX (0 400...600 mm, L - up to 30 m).

LITERATURE

• Dalmatov B.I. Soil mechanics, foundations and foundations. J1.: Stroyiz-dat, 1988.
• Dalmatov B.I. et al. Soil mechanics. Fundamentals of geotechnics. Part 1. M.; St. Petersburg, 2000.
• Ivanov P.L. Soils and foundations of hydraulic structures. Soil mechanics. M., 1991.
• Ukhov S.B. and others. Soil mechanics, foundations and foundations. M.: Publishing house ASV, 1994.
• Tsytovich N.A. Soil mechanics (short course). M.: Higher School, 1973.
• Design of foundations of buildings and underground structures: Textbook. allowance / Ed. B.I. Dalmatova. M.: ASV; St. Petersburg: SPbGASU, 1999, 2001.
• A manual on the design of foundations of buildings and structures (to SNiP 2.02.01-83*). M.: Stroyizdag, 1986.
• Foundations, foundations and underground structures: Designer's Handbook / Ed. E.A. Sorochana. M.: Stroyizdat, 1985.
• Ulitsky V M, Shashkin A G Geotechnical support for the reconstruction of cities M Publishing house DIA, 1999

4.1. GENERAL PROVISIONS

Industrial buildings, as a rule, are built using a frame structure. Post-and-beam systems made from standardized products are adopted as the main frame schemes for industrial buildings. For one-story, single-span buildings, frame and arched (spacer) frames have also become widespread.

The cost of materials and structures, their transportation often exceeds 60% of the total cost of building construction. Therefore, one of the urgent tasks of increasing technical progress in construction is reducing the material consumption and weight of structural elements of buildings.

In industrial construction, there are three possible options for making the load-bearing frame of buildings: reinforced concrete, steel and mixed (reinforced concrete columns, trusses or covering beams - steel or wood).

In some cases, with appropriate justification, an incomplete frame with load-bearing stone walls can be used. The frame option is selected taking into account the parameters of the spans, the type and load-carrying capacity of in-shop lifting and transport equipment, the degree of aggressiveness of the production environment, fire safety requirements, technical and economic indicators and other factors.

When choosing materials and types of building structures, the specifics of the local construction industry, geological and climatic conditions of the construction area and architectural and artistic requirements are also taken into account.

The frame of a one-story industrial building usually consists of transverse frames formed by columns and load-bearing covering structures (beams, trusses, arches, etc.), and longitudinal elements: foundation, crane, frame beams, rafter structures, covering slabs and ties. When load-bearing structures of coverings are made in the form of spatial systems - vaults, domes, shells, etc., they are simultaneously longitudinal and transverse elements of the frame. The frames of multi-storey industrial buildings made of standardized reinforced concrete elements of a certain manufacture are available with beam or beamless floors.

Frames with beam floors usually consist of transverse frames, on the crossbars of which floor slabs are laid. The frames are framed and assembled from vertical elements of columns and horizontal elements of crossbars, which are connected to each other at nodes. The transverse frame frames provide rigidity to the building in the transverse direction, and floor slabs, crane beams and steel vertical connections between columns provide longitudinal rigidity.

In case of significant horizontal loads in the longitudinal direction of the building, crossbars are installed, rigidly connected to the columns, which form the longitudinal frames of the frame. A reinforced concrete frame with beamless floors consists of vertical ko-1opn elements with capitals and slabs supported on these capitals, forming interfloor floors.

The load-bearing structures of industrial buildings form a load-bearing structure designed to perceive and transmit acting loads to the base of the building. Transverse frames can have either rigid or hinged elements. In one-story buildings, as a rule, a structural system is used with a hinged connection between the frame crossbar and the column and rigid embedding of the column in the foundations, for example, a two-hinged system. Other systems (three- and hingeless) can be used. The spatial rigidity of the building in the longitudinal direction is ensured by foundation beams, covering and floor discs, as well as connections. In spacer frames, the coupling of frames and arches with foundations can also be made using a hinged pattern.

In multi-storey buildings, various load-bearing systems are used: frame, braced and frame-braced. It is recommended to design the reinforced concrete frame of multi-storey buildings mainly using a frame system, that is, in the form of a frame frame in both directions.

Although the frame system requires a large consumption of materials, it provides greater freedom and flexibility in floor planning. It has found application in seismic areas, undermined areas and subsidence soils. Bracing and frame-bracing systems simplify the solution of pairing the nodes of crossbars and columns. A mixed design solution can also be used.

4.2. STRUCTURAL ELEMENTS OF INDUSTRIAL BUILDINGS

4.2.1. Classification of foundations

The dimensions, type and depth of foundations depend on the type of frame, the properties of the foundation, the design load, the presence of soil iodine and the level of soil freezing.

The depth of foundations is measured from the surface of the plan to the base of the foundation. If there is a concrete preparation of the foundation, the laying depth is taken to its bottom. When choosing the depth of foundations, the depth of freezing of soils and eliminating the possibility of freezing of thick soils under the base of the foundation are of decisive importance.

The standard depth of seasonal soil freezing is taken to be equal to the average of the annual maximum depths of seasonal soil freezing and can be taken from a schematic map (Fig. 57) where the isolines of the standard freezing depths of loamy and clayey soils are given. In the absence of long-term observational data, the standard depth of seasonal freezing should be determined based on thermal engineering calculations.

For areas where the freezing depth does not exceed 2.5 m, its standard value can be determined using the formula

where M, is a dimensionless coefficient, numerically equal to the sum of the absolute values ​​of average monthly negative temperatures during the winter in a given area, accepted in accordance with SNiP for construction climatology and geophysics; c10 - value taken equal, m, for:

• loams and clays – 0.23;

• sandy loam, fine and dusty sands - 0.28;

Rice. 57. Map of standard freezing depths for loamy soils

• gravelly, coarse and medium-sized sands - 0.30;

• coarse soils - 0.34.

The value for soils of heterogeneous composition is determined as gsday-weighted within the freezing depth. The estimated depth of seasonal soil freezing is determined by the formula

• for external foundations of heated structures - according to table. 7;

• for external and internal foundations of unheated structures - kk = 1.1.

In all cases of foundation construction, drainage of surface and atmospheric waters must be provided in order to protect the foundation and moisture.

Foundations for supports of a post-and-beam frame

The most common type of foundations for a post-and-beam structural design are foundations made from individual glass-type blocks (Fig. 58, 59, 60).

Depending on the perceived load, the cross-section of the columns and the depth of the foundation base, several standard sizes of foundations are provided. The blocks have a height of 1.5 and from 1.8 to 4.2 m with a gradation of 0.6 m, the dimensions of their soles in plan are from 1.5 × 1.5 to (1.6 × 7.2 m with a module 0.3 m. Dimensions of knee pads in plan - from

Table 7

Thermal coefficient kk

0.9×0.9 to 1.2×2.7 m with a module of 0.3 m. The height of the steps is 0.3 and 0.45 m, and the depth of the glass is 800, 900, 950 and 1200 mm.

Prefabricated foundations can consist of one popliteal block with a glass or a popliteal block and a base plate (Fig. 58 b). Podk

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What methods of connecting foundations are best to use?

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Tape-to-tape connection

To connect strip foundations with each other with your own hands, use the “tape-tape” method. The connection is made in the following order:

Scheme of connecting foundations using the “tape-tape” method.

1. They dig out the foundation to the depth of the base of the building. In this case, the length of the trench should be 1.5-2 m. They do not dig up the entire side, but only part of it, arranging a cushion of sand.
2. Holes are drilled at the base of the structure with a diameter the same as the diameter of the reinforcement. Holes for the middle part of the strip should be drilled to a depth of ¾ of the width of the strip foundation. In this case, a checkerboard order is followed, and a distance of 0.5 m is provided for the corner parts.
3. Reinforcement having a longitudinal slot necessary for the wedging liner is driven into the holes for the middle part of the tape. It may consist of wood. Reinforcing bars with a periodic profile with a diameter of 14 mm are driven into the holes.
4. The frame of the future foundation is formed using the outlets of driven reinforcement. For the purpose of joining subsequent parts of the base, outlets 30-40 cm long are provided. Subsequently, they are welded.
5. Making a decision on a rigid connection in the case of an open loop involves performing work similar to the previous description. But the use of reinforcement per unit area of ​​the base for connection, that is, at the contact points is greater.

Underground structures of buildings and structures are divided into groups according to different criteria. They can be strip and columnar, slab and pile, monolithic and prefabricated, concrete, wood, stone and metal. But in construction practice, a combined foundation is often used as the foundation of a house, which is a combination of different types of structures, materials and shapes. Such schemes are used in various situations, for example, for the purpose of economy or due to strengthening the bearing capacity of the foundation.

Monolithic strip foundations for columns

a - individual tapes; b - cross tapes

Typically, strip foundations have a constant T-section with a shelf at the bottom.

The protrusions of the brand shelf work like consoles, pinched in the rib. The shelf is assigned a thickness of at least half the reach of the console.

The foundation strip is calculated and designed in the same way as a monolithic continuous beam, in which columns serve as supports, and soil pressure on the base serves as the load.

Combination options

In the process of designing, constructing or operating a house, circumstances arise that require the installation of different types of foundations in one building. In this case, the combination is carried out according to one of the following schemes:

• the piles are tied not with a grillage, but with a high concrete strip;
• Brick or concrete blocks are laid between monolithic pillars;
• the slab is supported not on a sand cushion, but on piles;
• the house is built on a strip foundation, and the extension is built on brick pillars;
• Prefabricated blocks are installed on monolithic pillows.

There are quite a lot of options for combined foundations. One of the most common options is the installation of a monolithic reinforced concrete belt around the entire perimeter of foundation walls made of piece materials. This combination increases the reliability of the underground structure, providing the opportunity to combine different sections into a common system.

In this case, the strapping is the same grillage, but with increased dimensions in height. On the other hand, recessed pillars for a strip foundation provide additional support if it is erected on a weak-bearing foundation or on heaving soils. Ribbon-column structures have a number of advantages, namely:

• the permissibility of erecting massive structures in difficult geological conditions, even on horizontally moving soils;
• the ability to increase the strength and stability of pillars;
• the likelihood of a more even distribution of loads;
• the feasibility of building houses on areas with difficult terrain, including on slopes.

It should be noted that the combined strip-column type foundation has the positive properties of both types of structures - strip and column. During its construction, the volume of excavation work and the consumption of materials are reduced, since pouring a concrete strip to a great depth is not required. But the combined version of the foundation causes problems with the construction of basements or ground floors.

Reinforced concrete pillars are placed in the corners of the building, at the junction of load-bearing walls and evenly around the perimeter of the house. The reinforcement, placed in wells or pits, runs along the entire height of the tape and is connected to its frame. Thus, the foundation becomes a single structure.

Work on the construction of combined foundations is carried out in several stages.

First, a trench is dug according to the design documentation, and the installation locations for the pillars are outlined. As a rule, the width of the recess is 300-400mm, and the depth is 600mm. They dig holes under the pillars or drill wells below the freezing depth of the soil. A carefully compacted sand cushion 150-200 mm thick is placed along the bottom, the formwork is mounted just above the top mark of the tape or plinth and the reinforcement cages are laid according to the drawings. Often the structure being built is reinforced with metal profile beams.

The combined foundation is poured with concrete in a certain sequence. First, the wells or pits intended for the pillars are filled, and then the tape formwork is filled, but without significant interruptions in work. Otherwise, the required structural strength will not be achieved.

Example of a strip foundation under a bracing panel

It is recommended to determine the soil pressure diagram by taking the base as a linearly deformable half-space.

The calculation is made using a mixed method. For this purpose, the continuous connection of the beam with the base is represented in the form of a system of absolutely rigid rods, the forces in which are taken equal to the resultant soil pressure, uniformly distributed over the area of ​​the sole, corresponding

corresponding to each rod (Fig. below). Typically, the distances between the rods c are taken to be the same, and the number of rods (breakdown sections) is equal to 9-11.