One-sided increase in foundation support. How to strengthen the foundation: methods and technology for strengthening different bases

During the operation of buildings, it often becomes necessary to strengthen old foundations that have lost a significant part of their bearing capacity, as well as during the reconstruction of buildings, when the design load on the foundation increases.

Among the reasons leading to the need to strengthen the foundations and reconstruct the foundations, the main ones are:

periodic fluctuations in the level of groundwater;

wear of the foundations of old buildings under the influence of freezing, temperature changes, earthworks near the foundations, heaving of soils, exceeding design loads during operation, vibration exposure of equipment, etc.;

deformations due to design and construction errors;

suffusion (washout of smaller soil particles in the process of filtering flood waters through it.

Rice. one: Strengthening the foundation of an existing house

The existing technologies for strengthening the foundations of buildings are different and allow you to restore or significantly increase the bearing capacity of the foundation of any building. There is no significant difference between strengthening the foundation of a private house and a multi-storey administrative, industrial or residential building, but the methods of strengthening the foundations depend on the type of foundation being reinforced and the characteristics of the soil.

Ways to strengthen strip foundations

We list the main ways to strengthen strip foundations used today in practice by builders:

Reinforcement of foundations by gunning. A trench is torn off along the foundation in sections (grip), the surface of the foundation is thoroughly cleaned, notches are made on it, at least 15 mm deep, and then concrete is applied using a concrete gun.

Strengthening foundations with grouting. Without excavation, special mechanisms drill pits in the soil and foundation every 0.5–1 m along the perimeter (or only in a certain problem area), and with the help of special injectors, a concrete solution is supplied under high pressure; it fills the voids and cracks of the foundation and partially the space between the foundation and the ground.

Reinforcement of foundations with reinforced concrete clips. The foundation is opened in sections, cleaned, the base soil is compacted with jacks, the reinforcement frame is mounted and poured with concrete.

Strengthening the foundation with bored piles. Vertical drilling of wells is carried out through the supporting slab part of the foundation, the reinforcement of the pile with the reinforcement of the foundation is laid and tied, concrete is poured and rammed.

Strengthening the foundation with piles. Composite reinforced concrete piles are pressed into the floor of the foundation with a jack.

Reinforcement of foundations with injection piles. The foundation is drilled in several places through wells of small diameter at an angle to the vertical and not at the design depth. Reinforcement is laid and concrete is pumped under pressure.

There are other ways that can rather be called a variety of those listed above.

Reinforcement of foundations by reinforcing the sole

Strengthening pile foundations

Pile foundations can also be strengthened, if necessary, and there are the following ways to do this:

Often, the strengthening of pile and strip foundations is combined with the strengthening of the foundation soils.

Ways to strengthen reinforced concrete foundations

Reinforced concrete foundations can be monolithic (made by pouring concrete formwork with a reinforcing cage) or prefabricated (built from block reinforced concrete structures).

In construction practice, the following methods of strengthening reinforced concrete foundations are used:

Strengthening foundations by arranging a reinforced concrete clip

The use of a clip without broadening is resorted to if it is necessary to strengthen damaged reinforced concrete foundations with sufficient bearing capacity;
A clip with a broadening is equipped with insufficient bearing characteristics of the base or during the superstructure of the building.

Technology features:

A trench is dug along the perimeter of the base, the bare foundation is cleared of soil and washed with cement milk. Holes are drilled along the entire height of the base in a checkerboard pattern, into which reinforcing bars with a diameter of 15-20 mm are hammered (they must protrude from the wall by at least 15 centimeters).

Rice. 1.1

On the rods hammered into the foundation, a reinforcing cage is formed, to which sheet metal is welded. Concrete is injected into the voids of the foundation masonry through injection pipes until all existing cracks are completely filled. After the concrete has hardened in the foundation, the metal formwork is filled with concrete and the upper parts of the injection tubes are trimmed.

Strengthening the foundation with a reinforced concrete jacket

The method of arranging a reinforced concrete jacket is identical to the clip reinforcement technology, the only difference is the coverage of the base.

Rice. 1.2

Strengthening the foundation by increasing the area of bearing on the ground

The increase in the support area is carried out by increasing the thickness of the base with reinforced concrete sills.

Rice. 1.3

After digging the foundation, through holes are drilled in it, into which steel strands are inserted to fix the reinforced concrete ebbs. Upon completion of the fastening of the ebb, hydraulic jacks are placed between them and the wall and the formwork is unclenched. The resulting space is filled with concrete, the time is waited until it sets and the jacks are removed. Concrete is compacted, as a result of which the foundation is compressed both by the ebb itself and by the concrete layer.

Strengthening the foundation by increasing the depth of its laying

If it is necessary to transfer the base of the foundation to the underlying soil layer, concrete blocks are formed under the base of the house.

The foundation is unloaded with the help of rand beams and hydraulic jacks that raise the walls of the house. After that, pits are dug around the foundation in sections of 2-2.5 meters to a depth of 1 meter below the depth of the foundation. The walls and bottom of the pits are reinforced with a wooden fence.

Rice. 1.4

A well is dug under the supporting heel of the foundation, the size of which corresponds to the depth of the base increase.

After the concrete has hardened, hydraulic jacks are placed in the gap and the concrete is compressed in the well. Upon completion of the compression, the gap is concreted and the trench is backfilled with soil.

Strengthening the foundation with a second pile

Strengthening the foundation with bored piles does not require excavation of the base, which significantly reduces the time for reconstruction.

This method is used when it is necessary to strengthen foundations with insufficient bearing capacity due to improper design, the need to build a building or reduce soil density.

Additional piles can be placed either close to the existing foundation supports or carried out beyond the perimeter of the base contour. In this case, the load on additional piles is transferred using horizontal beams, by which they are combined with the grillage of the house.

Rice. 1.5

Reinforcement by bringing support elements under the sole of the base

This technology allows you to strengthen shallow foundations without increasing their depth and width. Monolithic reinforced concrete slabs or pillars are used as the supporting element to be laid, with the help of which an increase in the area of \u200b\u200bthe foundation support and an increase in its bearing capacity is achieved.

Rice. 1.6

Reinforcement of reinforced concrete foundation with a fall well

Lowering wells are prefabricated structures made of reinforced concrete slabs, which compress the soil around the walls of the foundation. The immersion of the well is carried out in the process of successive excavation of soil under concrete slabs. The trench formed around the walls of the foundation is covered with sand, which is poured with water and compacted in layers.

Rice. 1.7

Strengthening the foundation by restructuring its structure

There are frequent cases when, in order to strengthen the columnar base, a strip foundation is formed from it, and if it is necessary to strengthen the strip foundation, a slab foundation is made from it, in turn.
This method is resorted to with serious deformations of the foundation, when other methods of strengthening it are not able to provide the desired result.

Foundation soil reinforcement

The main factor provoking shrinkage of foundations is often insufficient density and bearing characteristics of the soils on which they are located. In this case, in combination with strengthening the foundation, work should be carried out to strengthen the soil. There are several ways to strengthen the foundation soils:

by injecting special chemical reagents into the soil that can change its structure (resinization and silicification); cementation - injection of cement slurry into the soil;roasting - by burning gas in special pits and wells;electrosilication.

Cementing- is carried out to strengthen rocky soil, gravel sands and sandy loams with a minimum content of dusty particles;

Cementing is carried out using special injection equipment - hollow metal pipes with a diameter of 25 to 80 millimeters are immersed into the soil along the perimeter of the base, on the lower part of which holes with a diameter of 4-5 mm are drilled in increments of 3 cm.

Rice. 1.8:

A cement-sand mortar is injected into the pipes with the help of a compressor under a pressure of 7 atmospheres. The pressure when supplying the solution is controlled by manometers. As a result of cementation, a concrete layer is formed under the base footing, which significantly increases the bearing capacity of the foundation.

Silicization- used to strengthen fine-grained soil: loam, quicksand, clay, and loess-like soil;

Silicization is carried out using similar injection equipment. Two types of solution are supplied to the soil through nearby injectors - sodium silicate (aka liquid glass) and a mixture of calcium chloride with water.

Strengthening of poorly permeable quicksand is carried out using a special emulsion - silicadol, consisting of sodium silicate and phosphoric acid. This mixture has a low viscosity and better penetrates into the pores of the loess soil.

Rice. 1.9

Silicization can be supplemented by an electrical effect on the sodium silicate solution, which contributes to a more uniform distribution of the emulsion inside the soil. With electrosilication, the effect of current on the solution is carried out for 2 days.

Bitumization- it is applied to rocky soil and dry sandy soil;

For bitumization, molten bitumen is used, which is fed through injectors into wells drilled in rocky soils. The bitumen that fills the voids hardens and prevents the erosion of the fissured rocky soil by groundwater.

Rice. 2.0

Strengthening of sandy soil is carried out according to the cold bitumization method, for which a bitumen emulsion (a mixture of bitumen particles with water) is used with the addition of coagulants (bitumen sediment catalysts). After the emulsion is injected into the soil, the bitumen particles fill the pores of the soil and create a soil-compacting watertight curtain.

Smolization- used to strengthen sandy soil;

A mixture of hydrochloric and carbamide acids is fed into the sandy soil through injectors. After entering the soil, the emulsion, as a result of a chemical reaction, forms a gel that fills the pores and glues the sandy soil together.

Deep compaction- used to strengthen bulk soils formed to level and raise the level of construction sites;

Deep compaction is carried out by arranging vertical and inclined bored piles. Drilling is carried out using CFA equipment (hollow auger) using a casing pipe, after reaching the design depth of the well, the drill goes up and fills the well with concrete mortar.

Rice. 2.1

Thermal strengthening (firing)- used to strengthen clay soil;

Roasting takes place in pre-drilled vertical and deviated wells. When strengthening foundations located on slopes, horizontal drilling of wells under the foundation of the building is practiced. Upon completion of drilling, a nichrome electric heater is placed in the lower part of the well, and the head of the well is closed with a hermetic seal.

The electric heater during operation (temperature from 300 to 500 degrees) rises from the bottom of the well to its upper point, as a result of which all layers of the soil are thermally affected.

Useful materials

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Due to the absence of planned repairs for a long time or under the influence of increased loads, the foundation begins to collapse. If the walls are quite strong, then the owners of the building decide to repair the foundation themselves. This allows you to extend its operational life and save some money. Strengthening the foundation of a private house is carried out in several ways, most of which do not require technical capabilities and specialized knowledge. The involvement of professional builders is necessary only in some severe cases.

Reasons for the destruction of the base

Strengthening the foundation is necessarily carried out, having found signs of deformation or planning to make changes to the existing structure. For example, if a decision is made to complete the second floor. Before starting work, it is important to determine the causes of destruction, since the choice of a set of restoration measures will depend on this.

Changes in the structure of the support can provoke:

Earthworks carried out on the site in the immediate vicinity of the building. By creating an additional load on a separate segment, they lead to the formation of subsidence and cracks.
Vibration. It is often observed if the house is located near the railway, as well as after earthquakes.
Strong soil moisture due to an increase in the level of groundwater, past floods.
Incorrect operation. One example is that the building is not heated in winter.
Violation of technology caused by insufficient volume of binder (cement), the amount of installed reinforcement.
Errors in calculating the maximum load.
The location of the base is above the freezing level of the soil, which causes it to move.
Remodeling of the building with the displacement of load-bearing walls.

Without eliminating the cause of the destruction of the supporting structure, repair work will be less effective.. Therefore, if the deformation is caused by a high level of groundwater, then it is first necessary to make a drainage system on the site and only then strengthen the base.

Repair of the foundation of a brick house

The most popular are several options for repairing damage. The simplest, when, with a slight subsidence, a crack went on the base. It is slightly expanded, cleaned of dirt and, well primed, sealed with sand-cement mortar.

In difficult cases, choose the method of installing a reinforced concrete pad, poured under the supports. Due to the large area, it reduces the load and, additionally insulating the soil, stops frost heaving. But the restoration of the base should be carried out in small sections up to two meters in length.

After waiting for one segment to be repaired to gain the necessary strength (within 25–28 days), they continue to restore the other. Therefore, this method is well suited to prevent subsidence of a separate part or one of the corners of the house. But strengthening the foundation in a circle in this way is a long process.

Filling the reinforcing belt is used if there are numerous cracks, while their number does not increase. The method allows you to prevent further changes, but the strength of the supporting structure increases slightly. The base is replaced when it can completely collapse. It is easier to perform such work with a wooden house, due to its low weight. Under the building of brick, stone, repairs are carried out in small pieces about a meter.

Before pouring the pillow, the problem area of the house is dug inside and out, trying to create two ditches up to 3/4 of the depth of the foundation and up to 3 meters in length. The presence of trenches will allow you to assess the condition of the support and decide on further actions to replace or restore it. Further:

A hole up to 2 meters long is dug under the pillow, deepening below the base by 40–50 cm.
Having covered the bottom with geotextiles, they make a sand bed 3–5 cm thick, and another 10 cm of rubble on top.
Additionally, a layer of sand is spilled and, having leveled it, a hard foam 50 mm in size is laid.
Having assembled the reinforcing structure, formwork is installed.
Bay concrete, the solution is compacted with a vibrator.
Leave to stand for 25-28 days.

You can move on to the next sections after the solution has completely hardened. If the repair work was not completed before the onset of cold weather, then the already finished trenches are covered with earth and covered with foam.

It is recommended to replace the plinth in separate pieces, no more than a meter long, keeping 3 m between the repaired areas. Considering the complexity of the work, you will need: a concrete chain saw for cutting and removing damaged parts, a welding machine for connecting reinforcing elements, a perforator. The order of work is as follows:

With the help of a saw, several vertical, then horizontal cuts are made in the wall, trying to divide the selected area into separate fragments.
After removing the pieces, all surfaces are cleaned.
Formwork is made, one part of which is installed from the side of the street, and the other inside the building. It should be 5–7 cm wider than its wall. If two indents fail, then one of the sides is erected flush.
Having prepared the formwork, a reinforcing structure is installed. For which, having drilled holes in the wall, vertical pins 18–22 mm in diameter are driven into it.
The blanks are placed in a horizontal plane, fixing them in the old base.
The reinforcement is connected to each other with a knitting wire, by welding.
At the end, they are concreted and allowed to stand for up to 25 days.
The replacement of adjacent sections is started no earlier than the specified period.

The device of the reinforcing belt can be performed on one or all walls at once. With this method, part of the load is removed, due to which it is possible to effectively strengthen the foundation of a brick house. Another positive point is its protection from frost heaving, which is very important if the building is located in an area with a high location of groundwater.

They operate according to the following algorithm:

Work begins with the creation of ditches around the foundation (on the inside and outside of the walls), deepening to a sandy, gravel cushion. The width is kept within 80–100 cm, smaller sizes will make it difficult to attach the belt to the base.
Having completed the preparation of the trenches, the soil, and then the layer of crushed stone poured on top of 10-15 cm, is compacted with a manual rammer.
To hide irregularities, an additional layer of sand is laid, and foam sheets 50 mm thick are laid on it. To protect it from welding, it is covered with a tarpaulin.
After 60–90 cm, holes Ø 18–25 mm are drilled in the foundation. Prepared cuts of rolled steel are driven into them. Grids are welded to the reinforcement, which must be additionally tied together with pieces of wire, placing them at a distance of 5–7 cm from the base.
In the lower part, in order to evenly distribute the load on the ground, another grid is installed.
After the reinforcing structure is created, the tarpaulin is removed and the formwork is fixed.
Start pouring concrete.

All work is carried out in stages, first the pillow itself is prepared, and after 2-3 days the strengthening belt. It is believed that in order to enhance the characteristics of the base, it must be allowed to stand for a month, but this is not always possible. Therefore, after the final pouring of concrete, after waiting 3–5 days, the formwork is removed and the trench is covered with soil.

Strengthening the foundation of an old wooden house

Work is carried out taking into account the degree of destruction, or when the structure has gone into the ground. In the first case, the methods listed above are used, in the latter, the building is raised. This solution facilitates access to the foundation and reduces the load on it. All furniture is removed from the house, as far as possible and the stove. When the dimensions and weight of the building are small, they try to raise it with the help of a log. To do this, use a bar 80x80 mm. Substituting it under one of the corners and making an emphasis from the log, pressing on it like a lever, they squeeze the wall.

A heavier old house is lifted using several jacks. Having installed them in certain places, the building is moved to the desired height and the base is built up with the help of bricks, concrete mortar. In serious cases, when the strengthening of one of the parties is not enough, the entire perimeter is strengthened.

Sometimes in the repair of an old wooden house they are limited to concreting corner sections.

Before starting work, problem areas are exposed by digging a hole about a meter in diameter from each of them, placing it below the depth of the base.
To get to the reinforcement, the old foundation is cleaned in some places.
The reinforcing mesh is attached by welding.
Having installed it, layer-by-layer pouring with concrete is carried out, after which it is left to harden.

You can increase the degree of reliability by simultaneously strengthening the corners and the most problematic places along the perimeter of the home.

To do this, having prepared ditches up to 0.5 meters wide, reinforcement is carried out with a reinforcing lattice with cell sizes of 20 × 20 cm. The depth of the ditches is limited by the occurrence of the old support. Having connected the base and the reinforcement together, the formwork is prepared and concreted.

One of the effective ways to increase the strength of the foundation of an old wooden house is the pile method, which is divided into several types:

Boronabivnaya. On the sides of the base, with an interval of every one and a half meters, wells of two meters deep are prepared. After waterproofing, reinforced structures are laid and concrete is poured.
With screw piles. The method is less laborious, but it is necessary to simultaneously maintain the direction of the rods and engage in their deepening, therefore, several people are needed for its correct implementation.

It is difficult to list the available options for strengthening the foundation of a private house. All of them were developed taking into account existing defects and based on the possibilities of their solution. But in each case, a set of works to increase the bearing capacity of the foundation is easy to perform independently.

Often, owners of private houses are faced with the problem of the destruction of the foundation. Most often this applies to old log or timber buildings. But sometimes strengthening is also required for the foundation of a new house, if the technology was not followed during the construction and natural factors were taken into account, for example, how deep the soil freezes in the territory. In some cases, the foundation is destroyed if any objects are built near the house. And, finally, the foundation needs to be strengthened if it is planned to add additional premises or add floors to an already finished building. If this is neglected, then an increase in the mass of the building can lead to subsidence, distortion of the entrance and window structures, the formation of cracks in the base, and even complete destruction.

Causes of partial destruction of the foundation

The foundation is the platform on which the structure is based. It distributes the mass of the building over the entire area and reduces the specific pressure on the soil. The performance and durability of the structure depend on its condition, since it is on the base that all the load from higher structures falls.

Deep cracks in the foundation indicate the beginning of destruction

But during the operation of the building, the foundation is often subjected to partial destruction. This may be due to the following reasons:

the location of the house on sloping terrain, in a seismically unstable area or next to the railway;
incorrectly drawn up project;
errors at the stage of calculating the planned load;
non-compliance with construction technologies during the construction of the platform;
the use of low-quality building materials;
improper arrangement of waterproofing;
a decrease in the quality characteristics of the base;
natural phenomena - flooding, oversaturation of the soil with moisture, freezing of the soil;
human economic activity - improper operation of the house, for example, lack of seasonal heating, construction or laying of communications in the immediate vicinity of the foundation, repair or completion of the house.

Since at the initial stage of construction it is not always possible to accurately predict what kind of load and natural factors the foundation will be exposed to, subsequently it will be necessary to resort to strengthening it. Strengthening the foundation ensures the reliability and safety of the operation of a private house, since it is suburban households that are most exposed to natural factors. If you ignore the problem, you may have to completely change the foundation, and this costs a lot of money.

Before starting work on strengthening the foundation, it is necessary to conduct a thorough analysis of the reasons that caused its partial destruction. As a rule, professionals with special equipment are invited for this. They evaluate the factors that cause foundation deformation and make recommendations to eliminate or minimize them.

Preparing to strengthen the foundation

Before strengthening the foundation, its external and internal inspection is carried out. During the external examination, the following parameters are determined:

building dimensions;
condition of supporting structures;
the presence of cracks and bevels.

During underground research, indicators are determined:

device and dimensions of the platform;
strength properties of the material used;
the depth of its bookmark.

Before starting work on strengthening the foundation, it is necessary to make sure that its shrinkage is over. It usually lasts at least a month. To understand that the shrinkage is over, gypsum beacons are installed across the identified cracks. Their condition will allow you to determine when you can start strengthening the base.

At the final stage of preparation for strengthening, the platform is unloaded. It may be complete or partial. An important factor is the prevention of distortions that will adversely affect during the restoration of the foundation.

To further strengthen the foundation, the building is raised with jacks

Partial unloading of the platform of the house is carried out using wooden or metal supports and struts.

In the basement, install support pads, stepping back from the wall 2 m.
Place a support bar on top.
Fasten the stands.
Then connect them with a beam to the ceiling, and then to the support beam using wedges.

For capital unloading of the platform, steel strapping beams are mounted.

Under the row of masonry, in which the bricks are laid with short edges to the wall, punch the strobes on both sides, keeping a distance of 2 m between them.
Place the tie beams in them and secure with 25mm bolts.
Using overlays, weld the joints of the beams, and fill in the gaps from the wall to the beam with a sand-cement mortar.
Punch holes in the lower part of the walls, keeping the distance between them no more than 3 m, insert beams into the holes.
Install the crossbeams on the support pads on both sides of the wall.

Base strengthening methods

In modern construction, different methods of strengthening the foundation are used, due to the rapid development of the building materials market:

widening of the sole;
piles;
reinforced concrete pillow;
basement replacement;
reinforcing belt;
reinforced concrete shirt;
cementation;
ebbs;
summing up new grounds;
clips;
shotcrete.

Various methods are used to strengthen the foundation.

Each of these methods has both advantages and disadvantages. Consider the most popular technologies.

Outsole widening

In practice, home owners most often resort to the classic, proven method of strengthening the foundation - the method of widening the sole. The sole is a reinforced concrete pillow on which the foundation rests. This method is the simplest, most reliable and relatively inexpensive. Several people with certain skills can handle the job.

An additional foundation is laid around the house, which plays the role of an auxiliary support.
The sole along the entire perimeter of the structure is fixed at several pre-marked base points, the number of which depends on the size of the building and the degree of destruction of the main foundation. Typically, the distance between the points is 2.5–3 m.
On the sides and under the foundation, excavation is carried out.
A reinforcing screed is laid under the foundation and evenly filled with mortar.
Air bubbles are removed using a concrete vibrator.
The side walls of the sole rise to the plinth by 15 cm.

The method of strengthening the foundation by widening the sole is the simplest, most reliable and relatively inexpensive.

Strengthening the foundation with piles

There are many types of piles with which you can strengthen the foundation.

Bored piles

Additional strength can be given to the structure with the help of bored injection piles. Recently, this technique has become very popular. But due to the use of innovative technologies, expensive materials, drilling equipment and the involvement of specialists, this method is considered quite expensive.

The essence of the technology is as follows:

After the solution dries, a new foundation of pile structures is formed, which, in terms of strength and reliability, resembles a monolith on which the structure is based.

Additional strength can be given to the structure with the help of bored injection piles.

Micropiles

In some cases, micropiles are used. Their diameter is 150–300 mm. In the process of drilling, it is possible to fill the wells with a solution. This method involves the use of drill rods. Remaining inside the pile, they provide more reliable reinforcement of the foundation.

With the help of micropiles, it is possible to strengthen not only the foundation, but also the soil

Video: strengthening the foundation with micropiles

Driven piles

Pressed piles are used to transfer the load to solid deep-seated soils. They are installed using special equipment. Beams mounted in the base provide a good connection between the foundation and piles.

Video: strengthening the foundation with pressed piles

The method of strengthening the foundation with remote piles is used at an increased level of groundwater. The foundation is taken out on piles. The connecting link between the piles and the foundation is a reinforced concrete beam passed through the foundation.

The foundation is carried out on piles

Metal tubular piles

Installation of metal tubular piles is carried out on both sides of the platform. For this, a welding method using special equipment is used. To install the piles, a reinforced concrete frame is mounted and connected to the beams supported by jacks.

Metal piles are connected with a reinforced concrete beam

Pouring reinforced concrete pad

The advantages of strengthening the platform by pouring a reinforced concrete pad are:

reduced pressure on the soil due to the large footprint;
additional ground insulation. This prevents frost heave, which is considered the most common cause of foundation failure.

The disadvantages of the technology include the impossibility of pouring the entire foundation, but only in sections of no more than 2 m, and the need to observe the drying time of each section before pouring the next one. Therefore, this method is used to strengthen one of the corners of the base, or in the event that the time and cost of pouring the foundation around is not fundamental.

Reinforced concrete cushion reduces the load on the ground and allows you to insulate it

Filling the pillow under the foundation takes place in several stages:

The repaired area is dug around outside and inside the building. At the same time, the blind area and the floor are removed, the earth is dug around the base in the form of two trenches with a length of 3.0 m to 3.5 m and a depth of ¾ of the depth of the foundation.
The condition of the foundation is assessed for the presence of cracks and destroyed areas.
If the base is in order, a hole is dug under the pillow up to 2 m long and 0.4–0.5 m deep relative to the foundation. The bottom of the pit should be level.
Geotextiles are laid in the pit, sand is poured in a layer of 3-5 cm and a 10-cm layer of crushed stone with a fraction of 30-40 mm.
To level the surface, clean sand is poured over the rubble, and then a 5-centimeter layer of foam is placed.
The reinforcing structure is laid on top and the formwork is installed.
The base is poured with concrete and compacted with a vibrator.
The formwork is removed after 2 days.
You can start repairing the next section no earlier than after 25-28 days.

It is important that the concrete contains as little water as possible. The optimal proportion of water to concrete is 1:4. But too thick concrete is difficult to pour into a trench, so it can be diluted with a plasticizer sold in hardware stores.

The height of the finished reinforced concrete pad must be at least 10 cm of the repaired section of the foundation. This will strengthen the base and reduce the pressure on the ground.

In winter, it is not recommended to repair the foundation by pouring a concrete cushion. If dug trenches remain, protect them from frost heaving: cover with earth and cover with foam.

Video: strengthening the foundation by pouring a concrete pad

Plinth replacement

If shedding or destruction of the platform has occurred in the area of \u200b\u200bthe base, this part must be replaced. It is easiest to replace under a wooden building, as it weighs less than stone or brick.

The easiest way to replace the plinth under a wooden building

Under a structure made of stone or brick, the plinth is changed in parts no longer than 1 m with intervals between sections of at least 3 m. To carry out the work, you will need:

fittings;
cement;
sand;
crushed stone;
plasticizer;
concrete mixer;
chain saw for concrete for cutting the necessary sections of the base;
perforator;
welding machine for fastening reinforcing elements.

How to replace the base with your own hands

Video: replacing the basement with the rise of the house

Filling reinforcing belt

If the platform is covered with cracks, but their number does not increase over time, then the repair is carried out by pouring a reinforcing belt. This makes it possible to prevent further destruction of the base and protect it from deformation at low temperatures, but its strength does not increase significantly. The reinforcing belt is allowed to be poured both along the entire perimeter and along one wall.

First of all, the foundation is excavated outside the building. The outer part of the foundation should be completely free from the ground, but you should not dig deeper than a sand or gravel cushion. The optimal ditch width is 0.8–1.0 m.
The outer part of the foundation must be completely free from the ground
Then it is necessary to compact the soil near the foundation by manual tamping and pour a layer of crushed stone with a fraction of 30–50 mm and a thickness of 10–15 cm. The crushed stone is also compacted. A thin layer of sand is poured over it to hide the sharp edges.
On top of the sand, a dense foam 5 cm thick should be laid and covered with a tarpaulin to protect the material from sparks during the welding process.
Further, in the foundation, it is necessary to drill holes with a diameter of 18–25 mm at a distance of 60–90 cm and drive pieces of reinforcement into them, which will serve as anchors. Trimmings should protrude from the wall by 15–30 cm.
Weld external and internal meshes made of reinforcement 10–14 mm thick to them, which should recede from the base by 5–7 cm. The meshes are connected to each other using pieces of reinforcement.
Reinforcing meshes are connected with reinforcement
In the lower part of the belt, an additional reinforcing mesh is arranged for a pillow with a thickness of 25–35 cm, and equal in size to the width of the ditch. The pillow reduces the load on the ground without the need to dig the foundation.
After creating a reinforcing mesh, remove the tarpaulin from the foam and install the formwork. Concrete is poured in two stages. After pouring the pillow, you should wait 2 days, and then proceed to fill the belt.
Concrete pouring is carried out in two stages
After 2 days, you can remove the formwork, and after another 3-5 days, fill the ditch with earth.

Pouring a reinforced concrete jacket

A common way to strengthen the foundation is to pour a reinforced concrete jacket.

The foundation for pouring a concrete jacket is dug out, taking into account the length of the tabs no more than 3 m

This method is quite simple. A person with the slightest skills in construction can pour a reinforced concrete shirt alone. This will require the following materials:

concrete grade M400;
fittings for tying the frame with a thickness of 16–18 mm.

Work order

cementation method

The method of cementation is also called injection. This is due to the introduction of hollow tubes into the platform cracks. As a rule, it is used to give strength to a rubble foundation that has many voids. Mortar is poured into them, and small cracks are covered up. This method is considered quite affordable, but it is used only for foundations with preserved bearing capacity.

The cementing composition is introduced using special injectors

Strengthening the base with ebbs

Sometimes the foundation is reinforced with ebbs. This technology is used to strengthen platforms made of brick or rubble. Reinforced concrete sills are used instead of the reinforcing cage.

The order of work is as follows:

Reinforced concrete sills are installed on both sides and squeezed out, while the lower part should touch the wall, and the upper one should not.
The structure is fixed with jacks and ties.
Then trenches are dug with a 2-meter grip.
The ditches between the wall and the resulting structure are filled with mortar.

Reinforced concrete sills are used instead of the reinforcing cage

This technology provides for increasing the strength of the platform with double-sided reinforced concrete clips or tubes through which the solution is injected. It fills all the voids of the masonry, due to this, the base is strengthened throughout the entire thickness.

At the initial stage, you need to dig out a part of the foundation to be repaired. Its length should be approximately 3 m, width - 1 m, depth - 0.5 m.
Then, on both sides, drill through holes in a checkerboard pattern and insert 20 mm reinforcement bars into them.
After that, it is necessary to attach a frame with cells measuring 150x150 mm to the reinforcement.
At the final stage, the formwork is installed and the resulting space is poured with concrete.

The method of reinforcement with clips allows you to strengthen the foundation throughout the thickness

Shotcrete reinforcement method

This technique is suitable for reinforcing a platform that is not too damaged or when planning to build additional floors. Reinforcement with shotcrete will reduce the pressure on the platform.

With this method, a concrete gun is used, so it is better to entrust the work to specialists. Strengthening the foundation is carried out in several stages.

Video: strengthening the foundation by shotcrete

Strengthening the strip foundation is carried out using a special technology and includes the following steps:

Video: strengthening the strip foundation

The most common cause of platform damage is ground heaving due to heavy rains, floods and freezing water. In this case, the building, as it were, is pushed out of the ground and warps. If the house is located in an area with close groundwater and an unstable climate, during construction it is necessary to think over the drainage system and arrange waterproofing of the foundation. The decision on how best to strengthen the foundation is made after studying the land and analyzing the damage.

The choice of methods for repairing and strengthening shallow strip and column foundations depends on the reasons for the need for strengthening, the design features of the foundations, the acting loads, as well as on the engineering and geological conditions and the degree of tightness of the working site. The organization and technology of work production essentially depends on the adopted method of strengthening or repair.

The main methods of strengthening shallow foundations with their brief description are given below.

Strengthening and restoration of foundation masonry by grouting. The method is used when the masonry is weakened throughout the thickness, and there is no increase in the load on the foundation. Cementation is carried out by injecting a cement mortar with a consistency of 1:1 to 1:2 or more into the voids of the foundation through injection pipes under a pressure of 0.2 ... 1.0 MPa (Fig. 7). Through one injector, a space with a diameter of 0.6 ... 1.2 m is filled.

Rice. 7 Strengthening the foundation masonry when it is heavily worn by injection of cement

solution:

1 - injectors; 2 - foundation; 3 - cement mortar

Usually the number of injection sites depends on the degree of destruction of the foundation masonry. It is advisable to carry out strengthening work with grips 2.0 ... 2.5 m long. Sometimes, to reduce the consumption of mortar, the side surfaces of the foundation are covered with cement plaster before grouting.

Repair and reinforcement of the body of foundations with polymer-based materials. The method is based on the use of polymer concrete, polymer solutions and mastics for sealing cracks in the body of foundations and injecting them inside. To seal cracks with a width of 2 mm or more and sinks with a depth of less than 50 mm, polymer solutions and polymer mastics are used. If the destruction is more significant and there are reinforcement exposures, restoration is carried out with polymer concrete or polymer mortar, applying shotcrete. In the presence of voids, cracks and other defects inside the body, injection treatment with polymer mixtures of resins with hardeners is used to strengthen it. Due to the high cost of resins, their injection is limited to small volumes of defects.

The device of protective solution shirts. The method is used in the repair of minor external damage to foundations. To do this, metal anchors are embedded in the masonry in a checkerboard pattern every 0.5 m, to which a reinforcing mesh is attached, and then a mortar is applied on coarse sand by simple plastering or gunning. Sometimes, instead of mortar, concrete is applied using air spray or laying in the formwork. This method is usually used in conjunction with other reinforcement measures. Due to the appearance of cracks in the steps of the strip foundation, they were reinforced by installing longitudinal reinforced concrete beams above the steps (Fig. 8). The beams are supported on buttresses, the width of which is determined by the calculation of masonry collapse at the intersection of the buttress crossbar with the masonry of the wall. The distance between the buttresses is based on the calculation of beams for bending. The entire foundation is enclosed in a reinforced concrete jacket, monolithically connected to the beams.

Rice. 8 Option to reinforce the laying of the strip foundation:

1 - foundation; 2 - cracks in the steps; 3 - longitudinal beam on the steps; 4 - buttress; 5 - shirt; 6 - rand beams; 7 - building wall

Partial replacement of foundation masonry produced during repairs with an average degree of destruction of the foundation body. The method is used when the load on the foundation increases, and the bearing capacity of the foundation is sufficient.

Strengthening reinforced concrete foundations with clips Due to the simplicity and reliability of the device, it has become widespread in practice. Clips, arranged without deepening the foundation, can be made both without increasing the area of the sole, and with its broadening. According to the material, they can be concrete and reinforced concrete. The latter are more reliable, as they cover the reinforced foundation, compressing it during concrete shrinkage.

Clips without increasing the area of the base of the foundations are rarely arranged. They are used in cases where the body of the foundation has insufficient strength, and its sole and base are in good condition.

Clips with an increase in the area of \u200b\u200bthe base of the foundation are arranged in shallow foundations made of various masonry, concrete or reinforced concrete. The manufacture of clips is possible both for the entire height of the foundation, and for part of the height (Fig. 9). This method is used if it is necessary to increase the load on the foundation and insufficient bearing capacity of the foundation. For these reasons, clips are often used to strengthen rubble and rubble concrete foundations during superstructures or other types of reconstruction of old buildings. Some schemes of such amplifications are given in Fig. ten.

Rice. 9 Schemes for strengthening strip foundations with concrete clips:

a - clip at the sole; b, c - trapezoidal and rectangular clips

to the entire height of the foundation body;

1 - foundation; 2 - clip; 3 - fines; 4 - reinforcement beam

Rice. 10 Options for strengthening rubble and rubble concrete foundations:

a - clips with their fastening with beams and shtrabs;

b - reinforcing elements; c - rigid metal frame;

1 - existing foundation; 2 - amplification clip; 3 - metal

beam; 4 - reinforcing bars; 5 - metal frame

Clips are arranged both in basement and non-basement buildings. Possible schemes for strengthening the foundations and basement walls with a clip are shown in fig. eleven.

Rice. 11 Options for strengthening walls (a), (b) and pillars (c) of the basement with clips:

1 - basement wall and foundation; 2 - pillar; 3 - clip;

4 - reinforcing bars; 5 - reinforcing bars; 6 - clamps

If it is necessary to significantly increase the areas of the sole, a more rigid system of unloading beams with a device of struts resting on the masonry is used (Fig. 9, c). To ensure rigidity in the longitudinal direction, the beams are interconnected with corners and reinforcing bars. After concreting, the foundation has an increased bearing capacity. On fig. 11, b shows a similar solution for a prefabricated strip foundation. The thickness of the casing and the required value of the sole broadening are determined by calculations, taking into account the increase in the design load in the event of reconstruction or a decrease in the bearing capacity of soils during operation. If necessary, not only to broaden the sole, but also to increase the strength of the body of the basement walls or columns, the holders of the foundations and walls are made uniform (Fig. 10).

After strengthening, the broadened part of the foundation begins to perceive part of the existing and additional loads. In cases of a large increase in loads, the broadening elements must be put into operation by preliminary compression of the base. Currently, there are a significant number of compression methods in practice. For strip foundations, in particular, a method can be applied, the essence of which is to install additional reinforced concrete prefabricated widening blocks on both sides of the foundation, the lower part of which is pulled together with reinforcing steel anchors passed through them and existing foundations. The upper part of the blocks is pressed from the surface of the foundations with wedges or jacks. As a result of this, the blocks turn around the lower point fixed with anchors, and the sole compresses the uncompacted soil of the base. After compression, the gap between the blocks and the foundation is wedged and filled with concrete (Fig. 12, a).

Rice. 11 Options for reinforcing prefabricated strip foundations with:

a - horizontal strokes and a monolithic clip;

b - metal frame and monolithic clip;

1 - foundation; 2 - clip; 3 - reinforcing bars

Rice. 12 Reinforcement options with base preswaging:

1 - foundation; 2 - blocks; 3 - strands; 4 - fixed tightening; 5 - clamping shield;

6 - anti-friction coating; 7 - wedges; 8 - transverse beam; 9 - crimped

base; 10 - jack; 11 - prefabricated banquet; 12 - concrete

There is another way of amplification with compression of the base. Its essence lies in the installation of clip blocks along the perimeter of the foundations, which are pressed into the ground by means of horizontal compression forces with strands (Fig. 12, b). To facilitate the immersion of the blocks into the ground, the contact surface of the blocks and the foundation is lubricated with antifriction materials. When tightening the strands passed through the pressure shields, the reinforcement blocks are compressed and slide down along the foundation, thereby compressing the soil. After compression between the blocks and the transverse beams passing through the wall of the building, wedges are installed, and the blocks are connected with a fixing puff.

The considered methods are suitable in cases where the foundation does not have consoles. If they are available, for example, the method, the scheme of which is given in Fig. 12, c. In this case, with the help of jacks, pressure is transferred to the foundation soil through pre-laid concrete elements, which is slightly less than under the base of the foundation. Before removing the jacks, spacer wedges are installed, and then a concrete clip is arranged

Strengthening by bringing structural elements under the base of foundations. Slabs, pillars and solid walls are used as additional elements brought under existing foundations. Possible amplification schemes are given in fig. thirteen.

In the case of a slight increase in the depth of laying with a simultaneous broadening of the base of the foundation, reinforced concrete slabs are brought under it (Fig. 13, a). To do this, in sections 1 ... 2 m long, the soil under the foundation is dug out and a monolithic reinforced concrete slab is made on site or prefabricated reinforced concrete elements are mounted. After the soil is compressed at the base, the gap between the slab and the base of the foundation is filled with concrete, carefully compacting it with vibrators.

Separate pillars under the foundation are brought in cases where it is possible to transfer the load to a more durable soil located at a shallow depth from the sole. The pillars are placed along a line or in a checkerboard pattern at a certain distance from each other (Fig. 13, b, c).

In case of insufficient bearing capacity of the base or, if necessary, a basement device, a solid wall is brought under the foundations (Fig. 13, d). Sometimes the wall is performed with a simultaneous increase in the sole area.

Rice. 13 Reinforcement options by bringing structures under foundations in the form of:

a - reinforced concrete slabs; b, c - individual columns; g - solid wall; 1 - foundation; 2‑pillar; 3 - pit; 4 - solid wall; 5 - plate; 6 - reinforcement cage

With a significant weakening of the foundation body and the need to deepen it, it is sometimes more profitable to do disassembly of the old and build a new one with the required depth. For strip foundations, the sequence of foundation operations is shown in fig. 14. First, unloading beams are passed through the wall, reliably resting them on supports made of sleeper cages or jacks. The latter are more convenient, as they allow you to adjust the position of the beams. After transferring the load from the walls to the supports, the old foundation is disassembled in separate grips 2.0 ... 3.5 m long and a new one is arranged at a deeper level. Between the new foundation and the wall, to ensure their joint work, a sand-cement mortar is injected under pressure. Then the excavation is backfilled and the unloading structures are dismantled.

Rice. 14 Reconstruction of the strip foundation with dismantling of the old foundation masonry

Change of constructive solution of foundations. In practice, reinforcement techniques are used by converting columnar foundations into strip foundations (Fig. 15). To do this, a reinforced concrete wall is arranged between the pillars in the form of a jumper, the lower part of which is brought under the sole of the existing foundation. The jumper also covers the under-column. In the case of a slight increase in the bearing capacity, the jumper can be made with a broadened sole. If necessary, a basement device is made with a jumper to the entire height of the pillars.

Rice. 15 Reconstruction of column foundations into strip foundations:

1 - columnar foundation; 2 - reinforced concrete jumper;

3 - reinforcing cages; 4 - widened part of the jumper

With a significant increase in the load, columnar foundations are converted into cross-tape and slab foundations, and strip foundations into slab foundations (Fig. 16).

Rice. 16 Reconstruction of strip foundations into slab foundations:

1 - strip foundation; 2 - holes in the strip foundation; 3 - supplied plate; 4 - omissions of the slab under the strip foundation; 5 - reinforcing cages

Strengthening foundations with piles. Piles are used to transfer the load from foundations to stronger soil layers in cases where the base has a high deformability and groundwater is observed, which complicates the process of widening or deepening the foundations.

In all cases, reinforcement is carried out in two ways: by transplanting the foundation onto external piles or by driving piles under the base of the foundation. Remote piles are used at a high level of groundwater, and supplied at a low one. In strip foundations, remote piles are arranged on one or two sides of the foundation; in columnar foundations, they are located both on two opposite sides and along the entire perimeter (Fig. 17). The piles brought under the sole can be installed in one, several rows or in bushes. The heads of the piles with reinforced foundations are connected by grillage, made in the form of reinforced concrete belts for strip foundations or reinforced concrete clips for column foundations. The length of the piles is assigned according to the calculation, depending on the characteristics of the soil and the loads on the foundation. In practice, a large number of ways to strengthen the foundations with piles of various design solutions are used. Some of them are discussed below.

Rice. 17 Strengthening strip and column foundations

1 - reinforced foundation; 2 - pile; 3 - grillage; 4 - rand beam; 5 - transverse beams; 6 - lever grillage

Reinforcement with stuffed and bored piles. Stuffed piles are arranged by immersion in the base of casing pipes with a diameter of 250 ... 375 mm, followed by extraction of soil from them and filling them with concrete with tamping or compaction with compressed air (pneumatic piles). Sometimes stuffed piles can be used, performed using screw punching technology. Wells are formed by spiral-shaped shells, during the penetration of which the soil is not extracted, but compacted. In the case of the installation of bored piles, wells are drilled, reinforcing cages are installed and the shaft is concreted.

When strengthening columnar foundations with stuffed and bored piles, the piles are first concreted. Then the heads of the piles with reinforcing outlets are connected with a reinforced concrete clip, performed around the existing foundation (Fig. 18, a). The ends of the piles must be buried in solid ground. For reinforcement, two, four or more piles can be placed, arranged symmetrically.

When reinforcing strip foundations, remote piles are placed in parallel rows on both sides of the foundation. The removal of piles is determined by the convenience of the location of drilling equipment. In cases of strengthening with remote piles of foundations from rubble masonry, they are arranged at the required height with grooves into which metal longitudinal beams (rand beams) are mounted. Transverse metal beams are installed under the longitudinal beams. The spacing of the beams is 2.0 ... 3.5 m. After installing the beams, a strip grillage is concreted on top of the piles. To ensure joint operation of the foundation and the installed piles, the gap between the grillage and the cross beams is wedged. The scheme of such a solution is shown in fig. 18, b.

Rice. 18 Options for reinforcing strip (a, b) and columnar (c) foundations with stuffed piles:

1 - foundation; 2 - grillage; 3 - stuffed piles; 4 - zone of compacted soil; 5 - metal beams; 6 - beam, concreted in place

In prefabricated strip foundations, a variant can be used, the scheme of which is shown in fig. 18, c. At the same time, holes are not punched in the foundation wall, and transverse reinforced concrete beams are made on the spot, combining them with reinforcing bars passed through the horizontal joints of the masonry. Beams work together with the wall due to the forces of friction and adhesion.

Strengthening by pressed piles. At present, a lot of experience has been accumulated in increasing the bearing capacity of foundations with pressed piles. Piles can be either solid or composite of individual elements. This method has a number of advantages: the absence of dynamic and vibrational effects on the building during the reinforcement device, there is no need for reinforced pile shaft reinforcement, high pile installation accuracy, minimal environmental pollution and low energy consumption during the device.

Strip foundations can be reinforced with the help of external pressed piles of tubular elements 0.8 ... 1.2 m long, located in pairs on both sides of the wall, a diagram of such reinforcement is shown in fig. 19, a. Piles are loaded with jacks, the forces from which are transferred to reinforced concrete beams, made together with a solid reinforced concrete belt, which is then monolithic with piles. The piles are pushed in simultaneously from both sides of the wall. The tubular elements, as they are pressed in, are joined together by welding. After pressing in, dismantling the jacks and thrust beams, the pile cavities are filled with concrete, the reinforcement and formwork of the pile heads are installed, and they are concreted through the holes in the beam. In some cases, piles under strip foundations can be brought in one row. The work is carried out from pits dug up to the sole or below the sole of the foundations (Fig. 19, b).

Rice. 19 Options for strengthening foundations with tubular driven piles:

1 - foundation; 2 - metal tubular piles; 3 - reinforcing cage of the pile head; 4 - head; 5 - reinforced concrete beam; 6 - wall; 7 - holes; 8 - jack beam; 9 - wedges; 10 - corners; 11 - jack

To transfer the load to the pile, a distribution cushion is installed between the jack and the pile. In order not to remove the jack after each indentation, it is welded to the pillow. After pressing the link, the jack piston is lifted up and the pile is increased by the next link. When the required number of links is pressed in, the pile is fixed with the help of corners and wedges, the jack is removed and the pipe cavity is filled with concrete, and the pit is filled with rubble concrete.

In construction practice, composite pressed reinforced concrete piles "Mega" are often used. Piles consist of three types of sections; head, privates and lower (Fig. 20). First, a hole is torn off below the base of the foundation and the lower section is installed. Then the head section is attached to it and a jack is placed on top, resting against a special distribution element. After pressing the lower section, the jack is dismantled, the head section is removed, the ordinary section is installed, then the head section is mounted and the jack is mounted again. After pressing the installed row section, the operation is repeated until the end of the pile reaches the design mark. At the last stage, the gap between the distribution element and the pile is wedged and filled with concrete. In the case of transferring large loads, Mega piles are made remote in two rows (Fig. 20, b). At the same time, they are connected by transverse reinforced concrete beams.

Rice. 20 Options for strengthening foundations with reinforced concrete driven piles:

1 - foundation; 2 - distribution element; 3 - reinforced concrete beam; 4 - wedges; 5 - jack; 6, 7, 8 - head, ordinary and lower sections of piles, respectively

Reinforcement with bored piles allows to work without excavation, exposing the body of foundations and disturbing the structure of the foundation soil. The essence of this method lies in the arrangement of rigid root-shaped piles under the foundation, which transfer most of the load to denser soil layers. The piles are made vertical or inclined using rotary drilling rigs, which allow holes to be drilled through the walls and foundations located above.

Reinforcing cages are installed in the wells and a cement-sand mortar or fine-grained concrete is injected through the injection pipes. A distinctive feature of this type of piles is their small diameter (127 ... 190 mm) and relatively large penetration compared to the diameter (more than 100). The most widespread bored-injection piles have received when strengthening the bases and foundations of reconstructed and restored buildings. Piles have significant tensile strength, so they are sometimes used as anchors in structures subject to horizontal forces. Some schemes of reinforcements with bored injection piles are shown in fig. 21.

Rice. 21 Options for strengthening foundations with bored piles:

1 - building wall; 2 - ceiling supplied; 3 - bored piles; 4 - existing piles; 5 - distribution plates

Strengthening foundations using the "wall in the ground" method. The method is used when strengthening foundations located near the foundations of other buildings, on a cramped site, in difficult soil conditions, etc. Structural reinforcement solutions (with deep walls or rectangular pillars) depend on the reasons for strengthening the soil conditions, the magnitude and nature of the loads on the foundation, as well as a number of other factors. For example, when constructing deep excavations or basements near the existing foundation, reinforcement is carried out by deep walls erected between the excavation and the foundation (Fig. 22, a). At the same time, the increase in the stability of the wall is achieved by the device of anchor fastenings. An increase in the bearing capacity of columnar foundations can be ensured by erecting deep walls or rectangular-section pillars around them with a two- or four-sided arrangement (Fig. 22 b, c), and sometimes in the form of a closed box (Fig. 22, d). The walls and pillars are connected to the foundation with a reinforced concrete clip. If it is necessary to simultaneously increase the stability of the base and strengthen the foundation, parallel deep walls are arranged, united by lintel walls of lesser depth (Fig. 22, e). Due to the conclusion in a rigid cage with this solution, the stability of the base is significantly increased and at the same time the foundation is strengthened.

Rice. 22 Schemes for strengthening foundations using the "wall in the ground" method:

1 - foundation; 2 - a wall in the ground or a rectangular pole; 3 - notch; 4 - anchor; 5 - a wall in the form of a box; 6 - deep tapes or walls; 7 - lintel walls

Sometimes the strengthening of foundations is carried out in combined ways, simultaneously arranging "walls in the ground" and piles, as well as using various methods of fixing soils and foundations.

Strengthening foundations with sinkholes allows you to increase the bearing capacity by enclosing the base soil in a rigid cage. A well (round or rectangular in plan) is lowered as the soil is excavated along the outer perimeter of its walls. At the same time, the base of the foundation remains intact and is enclosed in a clip (Fig. 23). The dimensions of the well in plan and its depth are determined by calculation, while the soil inside the well is considered as a body in a rigid holder.

Rice. 23 Strengthening the foundation with a fall well:

a - installation of a fall well before diving; b - immersion of the well to the design depth; 1 - foundation; 2 - well; 3 - pit; 4 - crimped base

When reinforcing the grillage, in the case of a large degree of wear, reinforced concrete clips are arranged. A possible scheme of the clip is given in Fig. 24, a. The reinforcement of the holder must be closed along the perimeter of the grillage.

If possible, it should be prestressed. In the case of floating soils and the presence of a large amount of water, reinforcement is carried out using the "wall in the ground" method (Fig. 24, b). Sometimes additional reinforced concrete tapes are brought under the grillage, thereby reinforcing the grillage and the upper sections of the piles (Fig. 24, c).

Rice. 24 Reinforcement of grillages of pile foundations:

1 - piles; 2 - grillage; 3 - reinforced concrete clip; 4 - cemented crushed stone; 5 - closed fence "wall in the ground"; 6 - reinforced concrete tape

Strengthening pile foundations in case of their insufficient bearing capacity can be performed crushing additional piles or building up existing piles with additional sections. Most often, additional remote piles are arranged. An example of the latter is given in Fig. 25.

Rice. 25 Option to strengthen pile foundations with remote piles:

1, 2 - piles and foundation grillage; 3 - hole for passing a horizontal beam; 4 - transverse beam; 5 - longitudinal beam; 6 - new grillage; 7 - additional remote pile

Quite often in the construction of buildings and structures, one may encounter a problem when the foundation is in disrepair.

In order to properly perform the necessary work, you need to understand the factors of weakening and subsidence of the foundation.

The main causes of subsidence of foundations

The main factors in the development of deformations in foundations are considered to be not only natural, but also man-made impacts.

Technogenic wear factors:

Building add-ons;
Construction of collectors, underground;
Construction of multi-storey buildings, under which a deep pit is dug;
Arrangement of drainages;
Groundwater rise;
Uneven settlement of the foundation;
Incorrect execution of construction works;
In some cases, incorrect calculations by the designer;
Faulty plumbing;
Vibration effects on the structure and building.

Natural wear factors:

Earthquakes;
Deformation of landslide slopes;
When permafrost soils melt, after which the foundations of structures and buildings subside;
Over time, rock materials are weathered from the foundation, which leads to erosion of the base;
The foundations of buildings are washed away if they are located along the banks of water bodies.

When cracking and delamination of its body is observed in the foundation, resulting from freezing, it must be strengthened with synthetic resins or cement mortar.

Types of strengthening foundations

a new foundation is being laid, while the depth of its laying increases;
strengthening the foundation body itself;
strengthening foundations with piles;
the area of support increases;
slabs are laid under the building;
additional foundations are being built.

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