Strengthening the foundation of a private house with your own hands. Technology of repair and strengthening of foundations. Foundation reinforcement technologies

It often happens that the walls of the old building are in excellent condition, and its foundation is gradually collapsing and cracking.

In order not to demolish the building, you can strengthen the old foundation of a private house with piles or any other method. This procedure is laborious, but if you carefully follow the instructions, it can be done on your own.

This article will look at how to strengthen the foundation in different ways and what materials and home tools will be required for this.

Reasons for the destruction of the foundation

Before moving on to strengthening the base, experts recommend determining the causes of its destruction. There are the following options:

1. Mistakes were made at the design stage. Before creating the foundation, it is necessary to perform calculations; it is also not recommended to save on building materials.
2. Material aging. Gradually even concrete top quality begins to lose its properties and collapse.
3. High pressure on the foundation. Many are completing the second floor in a private house, which is why the load on the base increases significantly.

Ways to strengthen the foundation

Often the foundation is reinforced with metal beams.

Strengthening the foundation of a private house can be done in different ways. All of them will require building skills and tools.

The most common ways to strengthen houses are:

• increasing strength with blocks;
• strengthening with concrete bandage;
• strengthening the foundation with piles.

Using blocks to strengthen

Block reinforcement scheme

This method will strengthen the foundation of the old house. It is suitable if the base is still strong and does not have much damage, as well as to strengthen individual sections. At the same time, the number of procedures and their cost will be minimized.

Mount the formwork in the trench, reinforce it with reinforcement and pour the concrete mix

To strengthen the foundation of an old private house with blocks, you will need to lay concrete material at the corners of the building. Thus, the footprint of the building is increased. Strengthening the foundation of a private house with your own hands is carried out according to the following instructions:

1. Outside the building, a trench is dug at all angles, while its depth should be approximately 60 cm more than the depth of the existing foundation. After the base angle, all soil is removed. The size of the trench depends on the parameters of the soil. But in any case, the thickness of the concrete pillow at each corner of the base should not be less than 50 cm.
2. Formwork is installed at the bottom of the pit.
3. Inside it is placed a frame based on reinforcement. In this case, the coating should not touch the old base, since the hardened block of concrete will settle over time.
4. The formwork is poured with concrete mixture, after it dries, the boards are dismantled, and the pit is covered with soil.

With this method of strengthening the base, all procedures should be carried out as quickly as possible, since the stability of the dug foundation will be reduced. In this case, the old base may crack, which will significantly reduce its strength.

Concrete bandage for strengthening

Concrete bandage is superimposed around the perimeter of the house

If the old base is cracked, it can be strengthened by creating a reinforcing monolithic layer.

This method involves strengthening the foundation of a wooden house not from below, but from the side, which greatly simplifies the process.

Concrete bandage is most often used when it is necessary to restore the strength of the building. The procedure for such a procedure is as follows:

Concrete bandage can be combined with block reinforcement. But in this case, you will need to first dig the corners and build concrete supports under them, and after they dry, carry out procedures with a bandage. Although such double reinforcement is heavier and more expensive in cost, it will provide more high level strength. For more on bondage, see this video:

Sometimes specialists use reinforcement of the base with the help of bore injections, but this method is more complicated and is practically not used for private buildings.

Strengthening with piles

How to strengthen the old foundation? Sometimes the only option for repairing an old foundation is to reinforce it with piles. There are several ways to properly perform the reinforcing procedure:

• screw;
• depressed;
• bored.

The screw method is considered the simplest. To carry it out, you do not need special knowledge, you only need tools and an assistant. The material used is a pipe equipped with a screw platform. It is she who creates the support for screwing the pile into the ground. Also, the helical platform allows, after installation, to distribute the pressure on the base.

You will have to twist the piles together with assistants

How to strengthen the foundation of an old house? To prevent possible destruction of the outdated foundation, it is necessary to exclude drilling procedures. For these purposes, the pressed method is used, in which the piles are pressed into the ground. This will protect the decrepit basis from destruction. However, this procedure cannot be performed on your own, you will need special equipment and assistants.

The bored method is the longest and most laborious. These procedures often take several months. Finished wells are filled with reinforcement and poured with concrete mortar. Piles are installed using anchors.

The scheme of strengthening the foundation with piles can be seen below.

When thinking about how to strengthen the foundation of a house, it is necessary to take into account a number of the following factors:

1. You can reduce the pressure on the base of an old wooden house by reducing the level of soil heaving. To do this, a pillow of sand is created under the base, and a clay belt is laid around.
2. Soil mobility will be significantly reduced if a drainage system is installed around. This will increase the density of the soil, therefore, the strength of the basis will increase.
3. Insulation of the basement and foundation will significantly slow down the process of destruction and increase the service life.
4. A sealed blind area will protect the base from precipitation.
5. To reduce the amount of moisture penetrating into the soil around the base, you can use a system of gutters placed on the roof. For more information on how to strengthen a crumbling foundation, see this video:

As can be seen from the article, strengthening the foundation with your own hands is a rather laborious procedure. You will need to decide on the method of strengthening and carefully adhere to the technology of the process. Also, for certain methods of strengthening the strip foundation, special equipment and additional assistance will be required.

Time passes, and the foundation of the building begins to slowly collapse. Almost every owner of an individual cottage or house faces this problem. How to strengthen such a foundation, how to increase its reliability?
Today, strengthening the foundation of a private house with your own hands can be done in several ways. But before doing such work, it is necessary to find out the cause of the destruction of the old foundation and choose a technique that partially strengthens the foundation under the house.

Reasons for strengthening the base

Strengthening the foundation with your own hands is required only when the following serious reasons appear:

• The mass of the building. The foundation of the brick house begins to collapse due to the heavy weight.
• Calculations are wrong.
• Extensions and additional buildings had a negative impact on the general condition of the entire structure.
• The state of the soil has changed.
• seismic impact.
• The redevelopment of the house was made without taking into account the additional load on the foundation. It was not taken into account in the design.
• Improper operation of the entire building. For example, there is no stock for Wastewater, house washing began.
• Severe ground vibration from blasting at a quarry or a nearby highway.

Ancient buildings have always had a strip foundation. It was characterized by negative operational properties. Strengthening the foundation of a wooden house, standing on such a strip foundation, can be done using an additional reinforced belt.
You can strengthen the foundation of an old house by replacing the old foundation. It is enough to raise the house on jacks, and strengthen the old foundation with an additional reinforced and concrete layer.
It is impossible to strengthen the foundation of a private brick house in a simple way, such as "we will mount the formwork, and then fill everything with concrete." This option won't help.
The depth of damage to the foundation of the house itself will tell you what strengthening method needs to be applied so that the first and second floors of an individual cottage stand for many more years.

Strengthening technique

We already understand how to strengthen the foundation of an old house. You can replace the supports of the columnar foundation, increase the thickness of the old foundation, or make a complete replacement.

Almost every owner knows well how to strengthen the foundation of a wooden, dilapidated house. But if the house is stone, there are many additional questions and problems.
It will take a lot of time and additional financial investments to tie such a heavy house with metal fittings. To reinforce the foundation of an old house with your own hands, you need a completely different technology.
Most of the stone buildings stand on strip base. How to strengthen the strip foundation, what needs to be done for this?

Shallow layer between the house and the soil

This base is directly dependent on the soil and all kinds of heaving phenomena. Lifting forces begin to put pressure on the base plate of the house, it begins to tilt. As a result, cracks appear on the surface, the base begins to collapse.
To bring the lifting forces into full balance, you need to constantly increase the area occupied by the sole.

Ribbon deep-buried foundation

On such a base, in which the sole is located under the level of freezing, lifting forces do not have any effect. But if this happens, the best reinforcing way is to increase the area of ​​​​the sole.
Sometimes such a base begins to wash out groundwater. Their actions are so strong that the soil literally “leaves” from under the foundation slab. Reinforced concrete monolith due to high humidity becomes less durable.
To save the base, it is urgent to mount a drainage system.
When the buried foundation began to crumble, to strengthen it, it is necessary to remove the damaged layers. Fill the opened surface with cement milk, and then carry out its hydrolysis.
If the tape of the base of the house is badly damaged, it must be built up with special reinforcing elements, for example, reinforced mesh. In this way, you will strengthen the foundation in a private house.

Additional amplification methods

Today, new technological processes have been developed to strengthen the supporting structure under the house. Some of them will be discussed.

Shotcrete

This method of strengthening the foundation for the house is used for strip foundations, when only the supporting foundation received damage. It is only required to carry out restoration work concerning the outer layer.
With the help of shotcrete, the basement of the house is strengthened, its water resistance increases. When this technique is applied, it is not necessary to install the formwork, the consumption of the concrete mixture is noticeably reduced.
Before you start shotcrete, you need to do some preparatory work. A trench is dug around the entire base of the house, with a maximum width of two meters. The base must be pre-cleaned of debris and dirt.
On the basis of the house, notches are made to increase the adhesion force of concrete to the base.
To strengthen the restoration layer and make it more durable, a reinforcing mesh is laid on the surface of the base for the building. Then everything is poured with concrete.

Sole expansion

Such reinforcement of the foundation of brick private houses is used very often. It is resorted to in case of deep damage, and when it is not required to involve special equipment. All work is easy to do on your own.
How to perform this procedure correctly? A layer of soil is removed from the left and right sides of the base of the structure. On the outer side, as well as its inner part, additional prefabricated ebbs are installed. They are tied at the bottom with through anchors.
Concrete mortar is poured into the resulting free space. The solution separates the base from additional ebbs. Above, the flashings can be attached to the foundation with rebar. The free gap is filled with soil. Its surface is well compacted.
The main difference between this technique, to expand the foundation for the house, from the installation of formwork, is the use and installation of ebbs made of a special, moisture-resistant material, as well as the installation of additional screeds.

Installation of an additional protective wall made of bricks

This method can be carried out without the help of professionals. All work is done by hand.
Similarly to the previous option, a trench is dug, no more than one meter deep. The surface is cleared of debris.
Structural defects are filled with cement mortar. From above it is closed with any waterproofing material. Usually a rolled roofing material is taken. A brick shirt is created on the surface of the roofing material. When all the preparatory work is completed, the ditch is filled with very greasy clay.

Reinforced concrete shirt

This reinforcement is columnar foundation. Near each reinforced support, but first a reinforcing mesh is installed. A wooden formwork is attached to it. The free space between the formwork and the base is filled with concrete mortar. Such a structure reconstructs the base, and also contributes to an increase in the bearing load on the pillars.

Pile technology

This technique has become popular when repairing the foundation of a brick house or any wooden structure. The only exceptions are dilapidated wooden houses with completely rotted lower crowns.
The technology of this method has two varieties. The use of the first is possible if the basement of the house has minor damage.
Holes are drilled through the bearing structural part until the drill touches the ground surface. Reinforcing bars are inserted into the drilled holes. Concrete is poured into the formed gaps, in small parts. To implement this method, you will need special equipment, as well as metal-concrete rods.

The second method, the so-called "pile-screw", is used to replace the entire foundation or strengthen it. This is especially true when a village house has a shallow foundation set on a rubble base.
First, pits are drilled, the depth of which exceeds the depth of freezing of the soil. Tubular supports are taken, they are treated with an anti-corrosion compound, and then installed in prepared pits.
This method got its name "screw" from the design of the piles. At their ends, special screw blades are installed. When the installation of piles is completed, the upper parts are cut off, the size is set according to building level. For a small wooden house, it is enough to install one pile under the four corners of the building. Unfortunately, the pile method is available only to a specialized team; it is very difficult to perform this method of strengthening the foundation on your own.
If you know the reasons that caused the destruction of the foundation, it will be possible to choose the right repair technique. This will help to completely eliminate all defects and minimize the negative impact of all causes on the existing foundation. Now you know in what ways you can strengthen the foundation and how to do it correctly.

During operation, the building is subject to redevelopment, expansion of buildings in the horizontal (extension), vertical (attic, second floor) level, underground structures wear out. Therefore, it is required foundation strengthening and grounds under it in various ways in accordance with the standards of the joint venture.

When do foundations need reinforcement?

Visually distinguishable reasons for the reconstruction, improvement or restoration of the performance of the foundations of the house are:

Guaranteed to take foundation strengthening in cases:

• construction of a new facility near an operated cottage on the same basis
• increase in prefabricated loads from an increase in the weight of load-bearing structures
• decrease in the strength of the materials from which the foundation was built
• weakening of foundations (soils) under the dwelling due to man-made or natural causes

For example, gusts of centralized life support systems (sewerage, village storm water, water supply) near the house can erode the soil, saturate the reinforced concrete structure with moisture, and increase the heaving forces. Or, when excavating soil from a pit near a dwelling, soils can move towards underground mining, reducing the design resistance of the base, the bearing capacity of the underground structure.

Note: The size of the sink funnel directly depends on the weight of the cottage.

Therefore, at the initial stage, a survey of load-bearing structures is carried out, the causes of destruction and deformation are identified.

The theory of strengthening bases and foundations

The above problems must be considered in combination, since foundations are created to transfer prefabricated loads from buildings to the soils under their soles. That's why foundation strengthening always begins with excerpts of pits to expose structures in places of crack formation, subsidence / shrinkage, concentrated loads (adjacency of internal load-bearing walls).

The causes of destruction, minor defects often become a blind area, a porch, a veranda, and other extensions that are rigidly connected to a slab, grillage or MZLF tape. Pit holes allow you to assess the contact of the base of the foundation with the soil, the degree of soil compaction. This will increase the bearing capacity of the foundation in several ways:

Before carrying out these operations, the foundation is jacked up to the design position in separate sections. In some cases, these measures are sufficient to restore performance. More complex options are the methods for restoring the foundation itself, described below.

Restoration technologies

Depending on the degree of destruction, changes in the geometry of the foundation, several methods can be used. However, before starting work, it is necessary to hang or partially unload the structure in use. The easiest way is to restore individual sections where the destruction of bricks and reinforced concrete has begun. It is more difficult to eliminate cracks, correct the geometry of sagging or skewed structures.

Heavy brick walls collapse when soils swell or shrink loose soils than log cabins, "skeletons", houses from SIP panels. These buildings, if necessary, can be completely raised to replace the entire grillage, move the building to a new foundation within the site.

Unloading the operated structure

For multi-storey buildings with slab floors, partial unloading can be used. The slabs are rigidly fixed in the walls, protruding from them in the form of consoles. Therefore, it is enough to make support platforms near the walls, place supports on them, drive wedges under them simultaneously on all floors, adjusting the lifting height with an accuracy of 1 cm.

In cottages, ceilings on beams are more often used, therefore, full unloading is used according to the technology:

• through holes are created in the MZLF tape by diamond drilling
• metal beams are passed through them, under which supports are mounted

Loose, not strong enough, brick foundations posted in a different way:

In addition, the beams can be jacked up to immediately install props of the desired length.

Attention: It is forbidden to make holes in the tapes with a perforator. Impact destruction of the structural material leads to the opening of numerous cracks, weakening the structure.

Strengthening the strip foundation

Loose, partially collapsed surfaces of brick and concrete strips can be strengthened in several ways:

• silicification - local injections into the drilled holes of the solution with the addition of liquid glass at a pressure of 0.4 MPa
• cementation - similar to the previous method, only cement milk is fed into the pits

Individual bricks can be dismantled from the masonry to be replaced with a new stone of the appropriate format. To do this, the remaining solution is removed, the nest is cleaned with a brush with a metal bristle.

Attention: The technology of bored small piles for self-restoration is practically unavailable, as special equipment is needed. Construction organizations rarely rent it out so that the property owner orders the service from them.

An extremely complex technique is to increase the depth of the MZLF, consisting of operations:

After that, the walls are hung out again, the jacks, the pick-up, the lower shield are removed, the remaining gap is filled with concrete. For tighter adhesion, the existing MZLF is embedded in a new design by 10 - 20 cm.

To reduce the complexity of operations by 30 - 50%, another method is often used:

Attention: Waterproofing, insulation of the outer edge, annular drainage are mandatory conditions for increasing the resource, eliminating swelling.

The original technology of reinforced concrete sills can increase the design resistance of soils under the foundation, while simultaneously increasing the strength of the structure itself due to lateral compression. The sequence of actions is as follows:

Thus, when squeezing out the upper part of the tides, they compress the soil under the MZLF, strengthening it many times. The jacks are removed after the concrete has cured, the stud usually remains inside the structure.

It is possible to widen the sole of the tape after digging the hole in two ways - to get concrete slabs on both sides or to mount the formwork, to lay concrete under the sole.

Columnar foundations can be strengthened using the submersible well method. Due to the fact that the grillage interferes with putting on the pole in operation, a ring of round or square section is cast in place into a removable formwork. Its inner size should be 40 - 60 cm larger than the outer section of the rack, so as not to violate the strength of the base under it.

In this case, it is not necessary to hang the walls, the soil is evenly removed under the ring from the outside, the structure lowers under its own weight. After reaching the design mark, the soil inside the ring is additionally compacted with a vibrating plate or rammer.

Attention: The backfilling of the sinuses between the well and the walls of the pit should be done with non-metallic material. This will reduce pull-out loads in case of possible swelling of the soil during freezing.

clip method

For tape and column monolithic foundation reinforced concrete can be used. This technology solves several problems:

• the operated underground structure will receive a new high-strength shell, rigidly connected to the tape, column
• due to the widening of the sole, the bearing capacity increases many times over
• building resource increases by 30 - 50 years
• it becomes possible to waterproof, insulate the clip to eliminate frost swelling of soils

The sequence of operations when making a reinforced concrete clip is as follows:

Attention: It is forbidden to expose areas larger than 2 - 3 m, so as not to cause the building to skew. The work is carried out sequentially, starting from the corners, before they begin, the foundation must be unloaded.

The drilling depth for laying reinforcement is 2.5 - 5 cm. The frames use longitudinal bars with a diameter of 8 - 14 mm from A400 reinforcement ("corrugated"). The spatial geometry of the frames is given by clamps made of A240 reinforcement with a smooth outer surface.

It is mandatory to provide a protective layer of concrete - all the rods must be recessed by 2 - 7 cm. It is preferable to connect the reinforcement with wire twists, which cannot be moved when the concrete is distributed inside the formwork. In foundation work, composite reinforcement is prohibited, which has a much greater ductility compared to steel.

There is a brick clip technology, which is rarely used, only for monolithic tapes MZLF. If the outer surfaces of the foundation are loose, it is impossible to widen the tape for a number of reasons, this technique is used:

• ledges are made on the sides of the MZLF - the concrete is cut with an angle grinder with diamond equipment in the upper and middle parts, a platform remains at the sole
• brickwork is carried out on a cement-sand mortar with support on this site
• surfaces are plastered, covered with waterproofing material

Attention: Monolithic structures always have a longer resource in comparison with bricks. Therefore, reinforced concrete "shirts" are preferable.

Clips for the column foundation are made one by one or for several columns at once, if they are located within 2 m from each other. Features of strengthening columnar foundations are:

This allows you to increase the bearing surface at all levels of the structure, increase the service life.

Reinforcement with bored piles

Wells for classic bored piles are made strictly vertically. Columnar foundations are made in formwork inside large pits. Therefore, this technology is a transitional option, it consists of several operations:

After that, the tip of the deep vibrator is placed inside, the mixture is compacted.

Attention: The supports can be loaded after a week at least. All this time, the foundation is hung out or stands on temporary linings.

Reinforcement with screw piles

Unlike the previous technique, the position of a screw pile screwed into the ground cannot be corrected. Therefore, two technologies are used:

Attention: There is a “bull” option in the corners of the MZLF, when the piles are immersed obliquely on adjacent sides, tied around the heads with a beam. In this case, external access is sufficient for the performance of work, the floors do not need to be opened.

• When driving piles, the requirements of the SP should be observed, placing them at a minimum distance from each other - 3 diameters or 1 m in the clear, depending on the design. It should be taken into account that:
• screw piles compact the soil, the bearing capacity increases due to friction forces
• bored piles, poured into the ground, have an uneven outer surface, the bearing capacity is high, but the pull-out forces during swelling are very large
• if bored piles are cast into a fixed tubular formwork, both the pull-out forces and the bearing capacity along the side surfaces are reduced
• it is more convenient to rest the rynd-beams on the heads, and not on the body of the piles, however, this increases the repair budget

The piles strengthen the foundations and foundations under them. It is more convenient to use screw modifications, to which the weight of the building can be transferred from temporary supports immediately. When pouring drilling structures, you will have to wait 3 days at least in hot weather, 28 days in the off-season. Foundations can be reinforced with SHS piles in winter if absolutely necessary. To carry out monolithic work, it will be necessary to heat up mixtures, formwork, and arrange film shelters.

Thus, the exploited foundation and the foundation under it can be strengthened on their own. To do this, it is necessary to make an audit, identify defective areas, apply the most appropriate technology from the presented methods.

Reasons leading to the need to strengthen the foundations

The foundations of buildings and other underground structures eventually get physical wear and tear as a result of exposure to natural and man-made factors. The mineral materials from which the foundations are made are weathered, watered and leached; wooden elements (beds, grillages, piles) decompose, metal reinforcement, beams, steel and cast iron piles corrode.

Cracks appear in the laying of foundations - the result of uneven deformation of the soil. Unacceptable wear of foundations can have a dangerous development with emergency consequences.

The foundations of structures (i.e. soils) may undergo deformations (precipitations, subsidence, dips) during operation. This leads to wear of structures, the development of cracks in the walls, rolls and deflections, and sometimes to a general loss of stability. The factors of wear of foundations and the development of deformations of the bases are man-made and natural.

Man-caused wear factors include: uneven subsidence of foundations - the process of long-term compaction of soils as a result of the load from the mass of buildings and structures. Observations show that the settlements of buildings develop over decades. For example, the hotel "Russia" in St. Petersburg, completed in 1961, by 1963 had an average draft of about 50 cm, subsequently, the development of precipitation continued at a rate of up to 0.5 cm / year, the bearing longitudinal walls of the building received deflection, dangerous cracks developed in them.

Rice. 1. Settlement of the Rossiya Hotel building in Leningrad (observation period 1963-1983). a - plan, diagram of the settlement of the outer walls of a 10-story building and 2-story extensions; b - cross section of the building and its base; c - diagrams of the sediment of the extension beams; I - band clay; 2 - layered loam; 3 - peat; 4 - sedimentary seams; 5 - places of the greatest damage to structures; b - installation points of deformation marks

Undermining the territory, i.e., the construction of underground structures in a closed way (subways, tunnel sewers) can also lead to uneven foundation settlements.

For example, yards, streets, buildings and structures above the subway tunnels settle by 4...6 cm per year, above stations - by 6...10 cm, under inclined escalator tunnels - by 30...40 cm or more.

Artificial lowering of the groundwater level, which occurs during the construction of drainage, storm and general sewerage. At the same time, the thickness of the aeration zone increases, the wooden elements (beds, grillages, piles) dry out and rot, the foundations receive a large and uneven draft.

An increase in the level of groundwater, leading to "flooding" of the bases; at the same time, loess soils receive subsidence, loose sands are additionally compacted, chemical suffusion of some minerals (gypsum, etc.) may develop, and local failures may form as a result of the collapse of arches of karst cavities in limestones.

The superstructure of buildings, which increases the loads on the foundations, often exceeding the design resistance R of the foundation, which led to the loss of stability of the foundation or to settlement, structural damage occurred, and the general wear of buildings increased.

Mechanical suffusion of the soil, i.e., the removal of fine fractions of soils by the filtration flow as a result of the work of drainage, sewerage, as well as when digging trenches, construction pits of underground structures.

Erosion of the soil during a break in a water supply or hot water pipes, which causes the formation of caverns, gullies in the soil at the points of entry of communications into the building, the development of dangerous deformations of the walls.

The impact of vibration on the foundations and structures of buildings from the influence of transport, industrial installations, building mechanisms. Vibrations lead to compaction of sands or liquefaction of water-saturated soil and loss of foundation stability.

The growth of the cultural layer in cities is an uncontrolled process of accumulation of bulk soils on the territory of cities and industrial zones. In St. Petersburg, the thickness of the cultural layer in places reaches 3-6 m. In the first decades of the city's existence, the authorities encouraged measures to raise territories as a means of flood control. In the XX century. the territory of the city was expanded due to the rise of alluvial coastal areas. Dumps of urban garbage, industrial waste were formed. As a result, the brickwork of walls and vaults, which had capillarity, was flooded with water, lost strength, and dampness arose in buildings.

Natural wear factors include:

Rice. 2. Typical situations leading to the dangerous development of deformations of the foundations of buildings and structures - a - construction of buildings in several stages; b - foundations for new massive equipment; c - construction of new houses on the site of demolished ones, d - construction of new buildings near existing ones; e - the same, but the existing building on piles; e - light extensions of massive buildings: g - the formation of a sedimentary funnel around buildings, deformations from the bridge, roads, communications, h - planning by filling areas near previously built buildings; and - counter roll of closely spaced buildings; k - additional draft during the superstructure; i - sediment of the base of the metal tank; m - draft of the warehouse of bulk materials; 1 - sediment plots; 2 - diagrams of additional deposits; 3 - boundary of the soil compaction zone, 4 - sedimentary seam; 5 - places of occurrence of damage to structures: b - foundations; 7 - blind area: 8 - pipeline; 9 - surface of the sedimentary funnel; 10 - backfill soil

Buildings and structures deteriorate over time, get moral and physical wear and tear, and are replaced by new ones. It is known that in New York, on the island of Manhattan, several "generations" of skyscrapers were built and then demolished and replaced with new ones. During the reconstruction of the center of Paris, London, Brussels, and other ancient cities, thousands of ancient buildings were demolished. At the same time, many cities or certain areas of cities have been declared “historical” by UNESCO, for example, Bremen and Lübeck in Germany, Ghent and Bruges in Belgium, Delft in the Netherlands, many cities in Italy, primarily Venice, cities of the Golden Ring in Russia ( Rostov the Great, Pereyaslavl-Zalessky, Uglich, Suzdal, Vladimir). For hundreds of years, some historical and architectural monuments have been preserved, such as the Cathedral of St. Sophia in Kiev, the Assumption Cathedral on the territory of the Moscow Kremlin, mosques and minarets in Samarkand and Istanbul, pyramids in Egypt and thousands of other valuable buildings. Obviously, the preservation of ancient buildings is possible through regular repairs, renovation of individual structural elements, including foundations.

In principle, foundations, i.e., structures located in the thickness of the soil, are protected from direct atmospheric and other environmental influences. They can be preserved for centuries even after the complete disappearance of the above-ground part of the buildings. However, under certain conditions, the foundations receive unacceptable wear, and the foundation soils - a dangerous development of deformations. In these cases, cracks appear in the walls of buildings, buildings can receive a roll (for example, the Leaning Tower of Pisa, St. Isaac's Cathedral in St. Petersburg), deflection, skew, which can lead to the collapse of the building as a whole or its separate part. In these cases, a special problem arises - strengthening the foundations and foundations.

The urgency of this problem has become apparent in recent decades, when mankind began to take care of the architectural heritage, as cities age, buildings in operation undergo major repairs and reconstruction. An important place in this direction of construction is occupied by geotechnical problems - the technology of strengthening and reconstruction of bases and foundations.

Structures and materials of foundations of ancient buildings. Foundations of buildings built in the 19th century. and earlier, in our time often require reinforcement. The foundations of such houses were made of local stone materials in limestone mortar, often included wooden elements - logs, sometimes massive masonry was performed on top of wooden piles driven into the ground.

On fig. 3 shows sections of the foundations of ancient buildings in St. Petersburg, according to numerous autopsies and surveys performed by SPbGASU employees in different years in connection with the development of building reconstruction projects.

Rice. Fig. 3. Cross sections of typical strip (a, b. c, d, e. f. i) and slab (zh. h) foundations of walls of houses built in the 18th-19th centuries. in the center of St. Petersburg (according to surveys carried out by SPbGASU specialists): 1 - brickwork: 2 - cobblestone masonry; 3 - masonry of split boulders: 4 - wooden piles: 5 - masonry of limestone; b - beds, grillage; 7 - basement floor: 8 - surface of the yard (street); 9 - concrete on broken brick

Foundation reinforcement design based on the general principles of design for limit states with the analysis of options.

In practice, it is required to consider the following main cases of the need to strengthen foundations:

a) in case of dangerous wear of foundations, development of soil deformations. In this case, it is required to strengthen the foundations of buildings and structures, fix the foundation soils. Such a problem arises in the development of projects for the renovation of architectural monuments and the dangerous development of damage to the structures of inhabited houses, threatening an accident;

b) with an increase in the load on the foundations and base in order to carry out the superstructure of buildings, replace equipment with a more massive one;

c) with an increase in the depth of basements and other underground volumes of buildings;

d) when designing construction in neighboring areas. In this case, preventive fixing of the base may be required in order to reduce additional settlement.

The design of foundation reinforcement is preceded by work on the inspection of the technical condition of above-ground structures, building foundations, as well as engineering and geological surveys and experimental work. In historical archives, drawings of foundations are usually missing.

Such projects in the XIX century. and had not previously been developed, the choice of the type of foundations, their shape, material, depth of laying and other parameters was the prerogative of the contractor, who relied both on many years, often purely local tradition, centuries of experience, and on the general instructions of state documents (“Charter of the Construction Russian Empire " and etc.).

Therefore, the initial information about the foundations, means of waterproofing the underground volumes of the building, soils of the bearing layer and backfilling of the sinuses of the foundations can be obtained by digging pits from one or both sides to the bottom of the foundations. Sometimes you have to dig deep enough pits - up to 3-4 m.

Having opened the foundation, the examiner makes measurements, on the basis of which he makes drawings (section and view of the foundation), establishes the type of material and mortar, takes samples of materials and soil from under the sole, which he examines in the laboratory.

The best results can be obtained by drilling out cylindrical samples (core) from the body of the foundations, which can be tested in the laboratory for strength.

Drilling allows you to identify the presence of wooden or other piles, grillages, to establish the position of their tip, without resorting to digging deep pits.

Signs of unacceptable (dangerous) deformations of building foundations are characteristic cracks in the walls (piers, interwindow lintels, brick vaults and arches floors etc.), distortion of the shape of the building box, which is established by high-altitude survey of the basement or foundation edge (according to its results, deflections, rolls, distortions of the walls can be detected), deviation of the walls from the vertical, floor shifts, distortions of flights of stairs and a number of other signs.

It is rational to combine the strengthening of bases and foundations with overhaul buildings. Sometimes these works are required to be carried out in inhabited houses or operated public buildings. Construction practice knows many cases when, after strengthening the base, the building or its block was straightened by means of jacks or, conversely, lowered, creating voids in the bearing layer of the base by drilling, which led to controlled settlement.

Of particular responsibility and complexity is the question of the possibility and conditions of building a building with one or more floors, since it is required to establish:

• whether the strength of the foundation body is sufficient;
  
• whether the bearing layer of the base will lose stability from additional load;
  
• whether the settlement that will occur as a result of the superstructure is permissible.

On this basis, a decision is made on the need to strengthen the foundation and foundation, a project for the reconstruction of the foundation and foundation is developed, and the technology of work is determined.

Calculation of reinforcement of the foundation and foundation of a building and structure

The first step in developing a foundation reinforcement project is to collect the loads transmitted from the ground part of the building along the edge of the foundation. The basis for solving this problem are dimensional drawings that are performed during the survey of the building. The original drawings of the building, if any can be found in the archives, are of secondary importance, since old buildings were usually rebuilt, including the addition of one or more floors.

The collection of loads is performed in the usual way. In this case, dimensional drawings of above-foundation structures and the results of measurements of the foundations of load-bearing walls and columns of buildings, opened by pits, are used.

The use of materials of engineering-geological surveys available in the archives or carried out on purpose does not always lead to satisfactory results, since the factor of soil compaction of the base under the long-term influence of the mass of the building is not taken into account.

More accurate data can be obtained from soil tests using two methods:

1) monolithic soil samples are taken in pits from under the base of the foundations, tested in the laboratory for compression and shear.

2) according to the data of manual dynamic sounding of the soil.

The first method is acceptable if the bearing layer of the base is represented by cohesive soils, the second, when sands lie under the foundations.

An example of the implementation of the first method can be a two-story superstructure project for a large-panel five-story house built in 1961. To determine the design resistance of the base, survey data from 1961 and test results of soil samples taken under the sole of the foundations of a bearing wall, performed in 1998, were used.

From the results of the comparison, it followed that the soil received significant compaction and hardening, the consistency changed from fluid to rigid plastic, the angle of internal friction increased from 6 to 24 degrees, etc. As a result, it was found that the design resistance of the base before construction R ol was 270 kN /m 2 , after 28 years of operation of the building R m =383 kN/m 2 , the existing pressure on the base of the foundations is 150 kN/m 2 , and after the superstructure with two floors it will increase to 200 kN/m 2 . Consequently, the foundation of the building has a significant margin and a two-story superstructure without strengthening the foundations is possible. It was also established that the base had a double reserve already at the stage of building construction, and the additional settlement from the superstructure would not exceed 3 cm.

The second method, based on the results of manual dynamic soil sounding, requires the use of a standard conical probe, which is fixed on a rigid rod and plunged into the ground by hitting a load of a certain mass.

An indicator of soil resistance is the number of impacts that ensure the probe is immersed in the ground by 10 cm (per "pledge"). By the value of the "deposit" is determined by the "conditional dynamic resistance of the soil", and by the bearing capacity - the indicators of mechanical properties (f, s, E). The obtained data is used to determine the actual design resistance of the foundation and the additional settlement (from the superstructure).

The need to strengthen the foundations is often dictated by the actual technical condition of the foundations, the signs of which are:

• the presence of decomposed wood beds, grillages or piles;
  
• low quality building stone (limestone, brick);
  
• poor quality or lack of masonry mortar;
  
• the presence of cracks in the laying of foundations, which are usually traced in the laying of walls;
  
• displacements and falls of masonry over openings made for laying communications;
  
• dips and cavities in the bearing layer of the base - the result of soil erosion, microbial decomposition of wood logs, etc.;
  
• the presence of layers and lenses of peat under the base of the foundations is the result of incomplete excavation.

Usually, these defects are detected when examining walls, ceilings, stairwells of a building, which have obvious defects - cracks, shifts in masonry arrays, ceilings, flights of stairs.

Protection of foundations from weathering

This measure is carried out during the physical and chemical weathering of the foundation material, when the masonry is not deeply affected by the weathering processes and there are no through cracks in the foundations. This usually happens if the foundations are made of rubble or brickwork with low strength and water resistance. Chemical weathering can occur when the cement or aggregate is not sufficiently resistant to the aggressive properties of the environment.

When restoring the surface of foundations, plastering with cement mortar (shotcrete) is used on the prepared (cleaned) side surface of the foundations or plastering on a metal mesh fixed on their side surface. If the weathering processes have captured the foundation to the full thickness, it is necessary either to cement the masonry, thereby strengthening the existing foundation, or to make a clip, restoring the bearing functions of the foundation.

Cementation of the foundation is carried out by drilling from the surface and from the first or basement floor in the foundation masonry of wells and injecting cement mortar into them. Wells are drilled with perforators or an electric drill with a diameter of 20-30 mm at a distance of 50 cm from one another, to a depth of approximately 2/3 of the foundation thickness. Tubes with a diameter of 20-25 mm are inserted into the wells, through which cement mortar is injected. The pipes at the wellheads are sealed with a thick solution to a depth of 10 cm. The injection pressure is 0.2-0.6 MPa. After test injections, it is necessary to dig out experimental areas, check the results and clarify the technology of work, scope of work, etc.

In cases where, due to weathering and destruction of the foundation masonry, cracks have formed in the above-foundation part of the building or structure, simply filling the open cracks with cement mortar may not be sufficient. Then it is recommended to increase the strength of the building or structure by other constructive measures.

Increasing the strength and broadening of the foundation

Traditional ways strengthening of the foundations consisted mainly in increasing the width of the base of the foundations, i.e., they provide a decrease in the specific pressure on the soil.

In addition, the bottom of the foundation was deepened to provide support on the underlying dense soil, and the rotten wooden elements were replaced with mineral material. This became possible with the deepening of the cellars. The foundation was broadened with a “butt” of building stone on mortar from two or one side; new masonry gave the broadened foundation a prismatic or trapezoidal shape.

A good example of such work is the reconstruction of the Finnish church of St. Mary in St. Petersburg in 1999-2001. The main problem was that under the foundations of the load-bearing walls and internal columns (pillars) a continuous row of wooden beds was laid, which had rotted into half a section, so cracks developed in the walls and brick vaults of the building. At high costs for the reconstruction of the building, it was decided to perform a complete removal of wood and replace it with reinforced concrete pads (Fig. 5).

Rice. Fig. 4. Examples of traditional ways to strengthen foundations: a - "butt" made of natural stone; b - concrete banquet; c - reinforced concrete clip: 1 - rubble masonry; 2 - Brick wall: 3 - “butt” made of stone: 4 - widening of the wall (brick): 5 - metal pins-anchors; 6 - concrete: 7 - steel reinforcement
Rice. 5. Reconstruction of the foundations and above-ground volume of the Finnish Church of St. Mary in St. Petersburg. Cross section of foundations, basement and above-ground volume (technological scheme)

Reconstruction of the foundations of the outer walls was carried out using double-sided pits. Dewatering was carried out from wells-wells, which were arranged in the basement of the building. The widening of individual foundations (pillars) for internal columns was more difficult to perform, since the depth of laying these foundations was insufficient, and it was necessary not only to widen, but also to deepen the base of the foundations. In these cases, the foundations were temporarily "hung out" with the help of metal beams, under the ends of which bars were placed, wedges were hammered between them. They provided compression of the "column - vault" system. After transferring the load from the column to the temporary supports, the foundations were dug up, deepened to the required value (usually up to 1 m), the resulting cavity was filled with cast concrete. Observations showed that the settlement of the walls was no more than 2…4 cm, columns 1…3 cm. This led to the formation of minor cracks, which were eliminated by pressure injection of cement mortars.

Strengthening the foundations of houses that have fallen into the undermining zone during the construction of the subway is usually carried out by bringing solid foundation slabs under the damaged building. These slabs are made of reinforced concrete and have the dimensions of building basement sections. The slabs are embedded in strobes, which are cut down in the walls of the basements, at the level of the existing floors. Such slabs work in conjunction with existing foundations, increase the overall stability of the base by reducing the specific pressure on the ground and increasing the overall rigidity of buildings.

The considered traditional technologies were easy to perform in dry soils, but very problematic in water-saturated soils, below the groundwater level. In these cases, the “butt” to the existing foundation was usually led above the level of its sole and above the groundwater level. Such amplification was not effective enough (see Fig. 4, a).

The work to strengthen the foundations by traditional methods was laborious, time-consuming and costly, and had a number of disadvantages. So, the “butt” and new slabs rested on uncompressed soil, which was included in the work only after the development of some draft, which could cause further development of the deformation of the building. For these reasons, they often tried to avoid the costly and laborious process of strengthening foundations, preferring to dismantle the building and build a new one in its place.

When reconstructing a production or building, when the loads on the foundation increase significantly, and also when cracks appear in the building and foundation as a result of uneven settlement, it is recommended to strengthen the foundation by making clips of concrete or reinforced concrete. In the old foundation, and sometimes in the basement part of the walls, chisels are made, holes are drilled into which embedded parts (beams, reinforcement) are installed, ensuring the joint operation of the old foundations and clips. In addition, reinforcement is installed in the clips, designed to ensure the strength of the walls in the longitudinal direction. In this way, the development of the bearing area of ​​the foundations is also achieved, i.e. the pressure on the foundation decreases, and consequently, the precipitation of the building decreases.

To ensure the joint work of the clip and the foundation of the torn rubble stone on a weak cement mortar, the clip is performed in trenches. Ties are inserted into holes drilled with perforators or punched in the old foundation. The adhesion of concrete to rubble masonry is determined by the uneven side surface of the masonry, cleaned of soil, washed and blown with compressed air.

On fig. 7 shows the strengthening of a concrete or smooth stone or brick foundation with a simultaneous increase in the support platform, also with the execution of the holder. The size of the keys in height is taken on the basis of ensuring the transfer of transverse forces from the cage to the existing foundation. It is desirable to carry out the clip with the use of expanding cement. If necessary, longitudinal reinforcement is inserted into the cage, for example, if there are cracks in the foundation, depriving the foundation of the necessary rigidity.

If it is required to expand the foundation with compression of the base under the expansion strips or to straighten the foundation and the wall, then the following technology is recommended (Fig. 8): in trenches, banquettes are arranged from prefabricated blocks or from monolithic concrete on compacted crushed stone preparation; punch holes through the foundation and stab along the foundation; install metal beams in holes; reinforced concrete beams are concreted along the foundation or metal beams are installed; jacks compress the base under the benches and, if required, level the foundation and wall; concrete filling or linings are arranged between the jacks; they take out the jacks and monolithic the structure.

Rice. 6. Increase in the area of ​​the sole of the rubble foundation: 1 - concrete clip; 2 - metal screed; 3 - wall; 4 - existing weakened foundation; 5 - crushed stone, rammed into the ground	Rice. 7. Increasing the area of ​​the sole of a brick or concrete foundation: 1 - reinforced concrete holder; 2 - dowels; 3 - longitudinal reinforcement

In a similar situation, it is convenient to use Freysinet jacks, which are flat plates made of two steel sheets welded along the contour with a thickness of 1-2 mm. Along the perimeter of such a hollow plate, a hollow roller with a diameter of up to 80 mm is made. A hardening liquid mixture is injected into the jacks, for example, cement mortar or epoxy resin, which, after compression of the base soil, remain stressed due to hardening (Fig. 9).

Rice. 8. Expansion and straightening of foundation deformations: 1 - existing foundation; 2 - concrete bench; 3 - longitudinal reinforced concrete beam; 4 - transverse metal beam; 5 - jack; 6 - crushed stone, rammed into the ground; 7 - concrete filling	Rice. 9. Expansion of the foundation using flat jacks: 1 - Freysinet flat jack; 2- reinforced concrete structure broadening; 3 - existing foundation; 4 - injection tube

The design of such jacks is very simple and they can be made in the workshop as needed. The shape of the jacks in terms of can be square, rectangular, round. Compression can be controlled by a manometer.

The required area of ​​the supporting surface of wooden cages, banquettes, temporary linings under the jacks is determined based on the increased loads on the ground during the hanging of above-ground structures. These live loads on bulk compacted soil are accepted up to 500 kN/m 2 , on clay undisturbed rigid-plastic soil - up to 1000 kN/m 2 , on sandy soil - up to 2000 kN/m 2 .

An example of an increase in the bearing area of ​​a free-standing reinforced concrete foundation is shown in fig. 10.

Piling

Modern ways reinforcement of foundations and bases are based on two principles: "transplanting" the building on piles and fixing the foundation soils by injecting mortar into the soil. In addition, these works usually include measures to strengthen the laying of foundations.

If there is a strong layer in the geological section of the base suitable for supporting piles on it, in projects for strengthening the foundations, the option of bringing piles under the existing foundations should be considered (Fig. 11 and 12).

Rice. 11. Bringing bored piles under the foundation: 1 - pile; 2 - grillage; 3 - jack removed before concreting; 4 - extensions; 5 - beam; 6 - concreting; 7 - existing foundation; 8 - fines	Rice. 12. Pairing the foundations of the existing building and extension: 1 - bored pile; 2 - grillage for an extension; 3 - a grid that combines grillages; 4 - cut down layer of concrete; 5 - exposed reinforcement of the existing grillage; 6 - existing grillage; 7 - driven pile; 8 - supporting cantilever ledge

Piles used to strengthen foundations differ significantly from piles used under normal conditions. When strengthening the foundations, bored piles, bored injection, indentation piles are used. Distinctive feature pile technologies is the need to use small-sized equipment adapted to work in low rooms (in basements, first
floors of buildings).

Rice. Fig. 13. Variants of constructive solutions for “transferring” reinforced foundations to vertical piles: a - with transverse distribution beams: b - with longitudinal ones: c - section along 1-I; 1 - reinforced foundation; 2 - wall; 3 - piles: 4 - transverse beam; 5 - longitudinal beam, embedded in the strobe

Bringing piles close to the wall is extremely difficult to work. To make bored piles, it is necessary that the minimum distance from the piles to the wall is at least 2.5 m.

At the same time, the transverse beams turn out to be bulky, which complicates their installation and causes high metal consumption. In addition, the drilling of large wells is accompanied by shaking, and often by moistening of the soil, which can lead to additional settlements of the building under load.

Vertical (boring, indented) piles are placed along the edge of the reinforced foundation in a row, they are combined with a monolithic reinforced concrete beam, which is embedded in grooves made in the body of the foundation, or fixed with anchor devices. With bilateral setting of vertical piles, they are combined in pairs with beams that are passed through holes in the old foundations.

Inside the building, work is even more complicated due to the cramped space and the inadmissibility of violations. technological processes enterprises, therefore, it is sometimes necessary to use such reinforcement structures in which the wall is suspended on cantilever beams, and part of the bored piles work for an increased load compared to the load on existing foundations.

Rice. 14. Strengthening the foundation with bored piles located outside the building: 1 - bored piles; 2 - anchors; 3 - beam; 4 - building foundation; 5 - monolithic beam termination

Often, pile driving and drilling are unacceptable due to ground conditions, the condition of the building, or requirements that exclude noise and vibration. In this case, pressed piles are used. The location of the piles can be closer to the wall and even under the existing foundation. To do this, you must first strengthen the foundation, and sometimes strengthen the wall, then, successively tearing off the pits under the foundation (1.8-2 m deeper than their soles), bring and press into the ground sections of metal pipes welded together and filled with concrete. The indentation is made with a jack. Sometimes such piles are pressed to a depth of 25 m. The advantage of these piles is the ability to determine their bearing capacity in the process of work.

Abroad, pressed piles from prefabricated reinforced concrete elements up to 100 cm long - Mega piles. The sectional area of ​​the piles is 20×20 and 30×30 cm. There is a through hole inside the piles. Permissible load: 400 kN for piles 30 × 30 cm and 200 kN for 20 × 20 cm. The distance between piles is assumed to be 1.3-2 m.

The installation of bored and driven piles requires the connection of these piles with the old foundation, which is done either with the help of metal structures (see Fig. 6 and 8) inserted into the openings and grooves of the foundation, or with the help of reinforced concrete clips (see Fig. 7).

The length of reinforcement piles is assigned in accordance with the geological section of the base so that the heel of the piles reaches the dense soil. Typically, the length of the piles varies from 3 to 20 m. The diameter of the piles is assigned depending on the equipment used, the length of the pile, the material and other factors; usually it varies from 80 to 250 mm. Piles are calculated by bearing capacity and buckling. The number of piles and the pitch of the piles in the rows are assigned depending on what part of the load from the bearing walls and columns is required to be transferred to the piles, assuming that part of the load is transferred to the base by the existing foundations.

Suppose the building needs to be built on, increasing the load along the edge of the foundations of the bearing walls p by 10%, the bearing capacity of the base has been exhausted, i.e. p \u003d R (R is the calculated resistance of the base). Therefore, the entire load from the superstructure must be taken by the piles.

Reinforcement of foundations and foundations during superstructures of buildings Superstructures of buildings are widely practiced and are considered as a means of obtaining usable area at the lowest cost. For example, in pre-revolutionary times in St. Petersburg, when the owner of a building changed, reconstruction was often carried out, the layout changed, the building was built on, the appearance of the facade changed. The study of historical materials showed that the superstructures were carried out several times and, for example, a one-story house turned into a two- or three-story one.

Obviously, the decision on the possibility of building a superstructure is largely determined by the technical condition of the foundations: the stability of the foundation and the amount of additional settlement. Even before the war in Leningrad, a rule was adopted that allowed an increase in the load on existing foundations without amplification by 25 ...

Methods of injection fixing of the "base-foundation" system

Bored injection piles differ from drilling piles in that a mortar (usually fine-grained sand concrete) is fed into the wellbore at a pressure of 1 to 3 MPa. This operation is called "pressure testing" of wells, while the soil surrounding the pile is compacted, and the actual size of the pile turns out to be 5 ... 10% larger than the nominal diameter of the well. Well drilling is carried out by various methods: "through" augers, with casing pipes or with flushing wells with drilling mud. Inclined piles are drilled through the foundation masonry and the base soil to a layer of sufficiently dense soil. These piles can be made from two sides, from one side (at different angles), from street level, from the basement floor, from the floors above the basement floor.

Rice. 15. Constructive decisions transplantation of foundations on bored-injection piles: a, c - one-sided setting of the pile; b, d - two-sided setting of piles; a, b - arrangement of piles from the floor of the first floor of the building; c, d - arrangement of piles in the basement; I - foundations; 2 - wall; 3 - overlap; 4 - beds (logs); 5 - bored piles

The method of injection fixing consists in the fact that the soil is saturated with mortars that fill the pores, give the soil increased mechanical properties and form closed volumes. Solutions injected into the soil fill cavities or zones of weakened (loosened) soil, compensate for the volume of wood beds, piles and grillages lost during decay. Over time, the mortars harden, thus achieving a broadening of the sole of the foundations and an increase in the depth of the sole, i.e., an increase in the bearing capacity of the base and a decrease in its deformability are provided.

Use of inkjet technology Its essence lies in the fact that a high-pressure jet allows mixing soil with cement mortar and obtaining a new material - cement soil, which has sufficiently high mechanical properties.

Rice. Fig. 16. Injection fixing: a - masonry: b - soil of the bearing layer (building of the New Hermitage. Implemented project, 2001): 1 - foundation: 2 - brick wall: 3 - injection well; 4 - half-decayed beds; 5 - array of fixed soil; b - basement	Rice. Fig. 17. High-pressure injection "jet grout" - technological scheme: a - drilling a well: b - start of jet injection; c - volume of fixed soil (completion of work)

Rice. 18. The use of "jet grout" technology for transplanting wall foundations onto fixed soil and forming retaining wall underground garage; 1 - wall of the house: 2 - rubble foundation; 3 - an array of fixed soil under the foundation; 4 - an array of fixed soil near the foundation ( retaining wall underground volume); 5 - pit; 6 - basement of an existing house: 7 - aquiclude

Recently, bored injection piles, also called root piles, have begun to be used to strengthen foundations. For the installation of these piles, there is no need to carry out large earthworks, manually punch openings and grooves in old foundations, clean the side surface for adhesion of new concrete to the material of the old foundation, and consume rolled steel.

From the surface of the earth and from the floor level of the first floor or basement, they drill vertically and obliquely through the existing foundation of the well until it rests on solid ground. The borehole diameter is usually 100-250 mm. This type of foundation strengthening is the most industrial.

It is especially advisable to use root piles to strengthen old foundations during the reconstruction of a building with an increase in loads on the foundation, as well as when there is a danger of disturbing the natural foundation by deep excavations or underground workings near the building. There are known examples of fixing old foundations of buildings in cases where a new building is being built nearby, under the load of which deformations of the base under the old building are possible. Unlike bored piles, root-shaped piles are drilled using machines with small dimensions and weight that do not violate the foundation and foundation soil.

Rice. 19. Strengthening of foundations with root-shaped piles: a - hanging; b - strengthening the foundation with piles-racks; 1 - bored (root-shaped) piles; 2 - foundation; 3- weak ground; 4 - solid ground

The technological line for drilling wells and devices for bored injection piles consists of SBA-500 drilling rigs, SO-48 (S-854) or SO-49 (S-855) mortar pumps, 4SGU-2 sieve hydrocyclone unit, receiving tanks and mortar conduits. Depending on the soil conditions, drilling with auger, cone bit, core barrel is used both without casing wells, and under the protection of either casing pipes or clay mud. For drilling in brick, masonry or concrete, heavy-duty drill bits are used.

High-strength core bits can drill even rebar of large diameters. After drilling is completed, a reinforcing cage is lowered into a well filled with a clay solution. This is usually done in sections 1-3 m long, depending on the height of the room from which the wells are being drilled.

Outdoors, the frame length may be longer. Then, injection pipes are lowered into the well, through which a cement-sand mortar is supplied. To clarify the bearing capacity of piles, it is recommended to conduct field tests. Principal design decisions for strengthening foundations and strengthening foundations during the design process are recommended to be coordinated with the construction and installation organization involved in the work.

LITERATURE

1. Allas E.E., Meshcheryakov A.N. Strengthening the foundations of hydraulic structures. - M. - L.: Energy, 1966. - 115 p.

2. Bransden D., Dornkemp J. Restless landscape. - M.: Mir, 1981. - 191 p.

3. Ganichev I.A. Device artificial structures and foundations. - M.: Stroyizdat, 1981 - 543 p.

4. Handel E.M. Engineering work during the restoration of architectural monuments. - M.: Stroyizdat, 1980. - 198 p.

5. Gersevanov I.M., Pol'shin D.E. Theoretical foundations of soil mechanics and their practical use. - M.: Stroyizdat, 1948. - 247 p.

6. Dalmatov B.I. Soil mechanics, bases and foundations (educational for universities). - M.: Stroyizdat, 1981. - 319 p.

7. Zurnadzhi V.A., Filatova M.P. Strengthening foundations and foundations during the repair of buildings. - M.: Stroyizdat, 1970. - 96 p.

8. Cambefort G., Puglis R. Lifting a building with mortar injection. Per. from French, 1971. - 23 p.

9. Knorre M.E., Morgunov N.S., Kol S.A. and others. Experimental caisson of Volgoyarstroy. - M. - L.; Gosstroyizdat, 1939.

10. Konovalov P.A. Bases and foundations of reconstructed buildings. - M.: Stroyizdat, 1980. - 133 p.

11. Legget R. Cities and geology. Per. from English. - M.: Mir, 1976. - 558 p.

12. Guidelines for the design of the foundations of buildings and structures. - M.: Stroyizdat, 1978. - 375 p.

13. building codes and rules. Foundations of buildings and structures. SNiP 2.02.01-83. - M.: Stroyizdat, 1984.

14. Sorochan E.A. Bases, foundations and underground structures

15. Shvets V.B. Tarasov B.L., Shvets N.S. Reliability of foundations and foundations. - M.; Stroyizdat, 1980. - 157 p.

16. Ulitsky V M, Shashkin A G Geotechnical support for the reconstruction of cities M DIA publishing house, 1999

The house, unfortunately, is aging faster than we would like. And if you feel that the floors began to sag under your steps, you noticed that gaps had formed between the floor and the walls, and your wooden house had a slight skew, then there were problems with the foundation.

An example of strengthening an old foundation

This indicates the need to repair the foundation of the house. And it's better not to delay it. Here we will look at how to strengthen the foundation for an old wooden house with our own hands.

Examining Foundation Problems

Before proceeding with the repair, it is necessary to make a simple analysis of the state of the foundation of the old house, the results of which will determine the method of its restoration. To do this, a ditch is dug along the entire foundation tape.

The moat should have a width of 70-90 cm and be located as close as possible to the base of the house in order to be able to reveal all the defects of the old foundation.

After that, it is necessary to carefully study the state of the foundation, paying attention to the following characteristics: the material from which the foundation is made, the technology for erecting the foundation, as well as the quantity and quality of damage to the foundations.

Repair of the foundation made of rubble mixture

If the analysis of the condition of the old foundation showed that the foundation of your house is made of rubble mixture and is in a satisfactory condition (damage and destruction are of a point nature), then pouring the foundation is the right solution to your problem. Strengthening the foundation in this way is quite easy and affordable. And although this method of restoring the foundation of a house is not the most reliable, it can be easily done by hand.

This method consists of several stages:

1. The old base is cleaned with a metal brush or grinder with a special nozzle.
2. They reinforce the old foundation, for which they drive reinforcing bars into it very carefully, so as not to completely destroy the old foundation.

An example of reinforcement of a destroyed foundation

• Problematic fragments of the destroyed foundation are removed from the common foundation tape.
• The foundation is poured with a lean mixture of concrete. Pour the mixture not all at once, but in portions. This will enable the concrete mixture to saturate all the voids of the old foundation, strengthen it and make it monolithic. To prevent the mixture from being absorbed into the surrounding soil, formwork and transverse partitions are made.

We repeat that this type of foundation restoration is not the most reliable, and therefore, to achieve the strength of the foundation of your home, you should use one of the methods described below.

Brick foundation repair

In the case when the analysis of the existing foundation showed that it was made entirely or partially of brick, then you can use the method of restoring the old foundation, which is based on the principle of expanding the old foundation by creating an additional reinforced concrete belt.

However, this method should not be used if there is a clear skew of the building.

The process of restoring the old foundation by creating an additional belt has a number of features:

An additional foundation belt filled in this way makes the old foundation stronger and more reliable. This is due to its expansion, as well as due to the connection of the old foundation through anchors with a reinforced concrete belt.

However, we note once again that it will not be possible to strengthen the old foundation by this method in the case when the house has obvious distortions.

Complete foundation replacement

If you find that your house has tilted, then be prepared for the more difficult and time-consuming process of restoring the old foundation - replacing it completely.

Before strengthening the foundation, determine the reasons that caused these problems. Most often, it deteriorates under the influence of groundwater or due to subsidence of the soil. In any case, it is necessary to take into account these reasons and further secure the foundation of your home from their impact.

If the cause of the destruction was groundwater, but it is necessary to pour the foundation in higher soil horizons and provide a good waterproofing layer in it. If the cause of the destruction was subsidence of the soil, then it is necessary to strengthen the soil by any method available for this.

So, first you need to raise the house above the old foundation. You can do this with the help of special equipment, or you can do it yourself.

Scheme of strengthening the old foundation

To do this, you will need a five-ton construction jack. Jacks are installed at the corners of the building on any flat base, which will prevent the jacks from being pressed into the soil.

Jacks alternately rise to a height of up to 1.5 - 2 cm. Do not raise the corners sharply (more than 2 cm at a time).

This can lead to the destruction of the structure of the house. The building must be raised smoothly, without additional distortions, which will preserve its integrity. However, in the process of raising the whole house, it is necessary to monitor the condition of the middle walls of the house. Best under them after partial uplift house to bring metal supports.

Upon completion of raising the house to the required height, the corners of the building must be fixed in this position. To do this, you can use metal channels or ordinary wooden bars. The main thing you should pay attention to when selecting channels is their reliability and durability.

An example of raising an old house to install a new foundation

As a result of all these manipulations, the house appears to be floating above its old foundation.

Consider the condition of the foundation. If the percentage of violations of the integrity of the foundation is more than 50%, then such a foundation requires its complete replacement.

This is done by hand as follows:

If, in the presence of subsidence, you are still not ready to change the foundation completely, then you can resort to arranging an additional reinforced concrete belt by connecting it to the old foundation by means of anchors. But this measure will only temporarily solve the problem with the destruction of the foundation of the house.

Repair of a pile wooden foundation

This repair is carried out in cases where the foundation of the house is the so-called "chairs", or in other words, log piles.

Complete replacement of the pile foundation made of wood

No matter how the wooden supports are processed, sooner or later, under the influence of moisture, they begin to rot and collapse.

In this case, there are several options for repairing the foundation with your own hands:

• replacement of piles with the same wooden supports;
• replacement of rotten wooden supports with stone, brick or reinforced concrete;
• replacement of the columnar foundation with a strip one.

The work on repairing the pile foundation can be divided into several main stages. Let's dwell on each of them in more detail.

Stage 1 - Dismantling the plinth and stripping the old foundation

At this stage, a part of the basement is dismantled so as to provide free access to the foundation.
For the same purpose, the base is freed from lags, boards, etc.

Stage 2 - Installation of a temporary support

Installation of a temporary support is carried out at a distance of 50-110 cm from the old rotten base. They mount a temporary hut under the lower crown of the house on both sides of the chair.

With the help of jacks, it is necessary to raise the house above the collapsed foundation. And again, we draw attention to the fact that this must be done very carefully, alternately raising each corner of the house by no more than 1.5-2 cm at a time. Upon completion of this stage, it is necessary to bring temporary supports under the lower crowns of the house, wedging them.

Stage 3 - Replacing the old chair with a new one

Now they are dismantling the old supports and installing new chairs in their place. In this case, it is necessary to ensure that the new supports clearly fit into the grooves of the old chair. At this stage, some problems may arise. Let's dwell on them in more detail.

1. A violation of the integrity of the plaster is likely: cracks may appear and even peeling of layers of plaster on the walls. This is a minor problem that is easily solved after setting the house on a new stable and solid foundation.
2. Distortions of internal openings of doors and windows are possible. This problem can be avoided by installing stronger reinforced concrete or stone pillars instead of wooden supports.

We examined the do-it-yourself repair algorithm for a columnar foundation associated with the replacement of old foundation pillars with new ones.

replacement of old foundation pillars

If you decide to replace the old, columnar foundation with a more durable and reliable tape one, then you should adhere to the following algorithm of actions:

Please note that in the case when the old building stood on a foundation with a low level of penetration, then after arranging the new foundation, it is necessary to ensure good drainage and build a blind area.

Do-it-yourself repair of the foundation of an old wooden house - how to strengthen and strengthen it

How to strengthen and strengthen the foundation of an old wooden house. Do-it-yourself repair and grouting of the foundation.