Why is it necessary to bury the foundation below freezing. Installation of the foundation above the freezing depth. Insulation of soil under light outbuildings and roads

The foundation is a rectangular reinforced concrete structure, which is responsible for the strength and durability of the building. The strip foundation is used to lay structures from various materials, the density of which is more than 1000-1300 kg / m 3.

The main parameter when creating a strip foundation is the depth to which it is necessary to dig the future location of the structure (the depth is directly proportional to the cost of construction).

Bookmark

The main factors that affect the depth of the strip foundation:

• soil characteristics (type, freezing depth);
• groundwater;
• the massiveness of the building.

Shallow

For the establishment of this type of strip foundation, non-porous or slightly porous types of soils (for example, sand) are suitable. A shallow depth is possible due to the properties of the soil or uniform swelling, which will not affect the integrity of the structure.

Suitable for wooden, brick and aerated concrete buildings. The main condition for laying the structure is the absence groundwater on the surface of the soil. If everything meets the requirements, you can save computational time and money. All you have to do is remove the topsoil and dig down to a solid layer of soil. Depth 0.5-0.7 meters.

Recessed

If the construction of a heavy building will be carried out on heaving soil (loam, clay, sandy loam, etc.), the most suitable option would be a recessed type of strip foundation.

• Before designing, computational operations are carried out, which make it possible to identify the depth of soil freezing and the level of groundwater.
• The depth of freezing can be determined using special books and tables. The groundwater must be measured independently. On a certain soil, we drill a well three meters deep, place a pipe inside. Throughout the year, we make observations to determine the level to which the groundwater rises.
• If the waters do not reach the freezing depth (distance of two meters), then to lay the foundation, you should dig a trench 3/4 of the freezing index (from 0.7 meters).
• If the groundwater rises above the established mark, then the soil freezing indicator is used to lay the strip foundation and another 0.2-0.3 meters is added.
• For heated buildings, in the design of the strip foundation, it is not calculated without the freezing indicator.

Advice! It is necessary to pour the foundation and complete the construction of the facility during the heat season.

• For unheated buildings, the soil freezing rate should be increased by ten percent of the original. In heated buildings, the value is reduced by 25%. If the building is equipped with a basement, measurements are taken from the beginning of its floor.
• Dry and sandy soils imply the laying of a strip foundation above the freezing point of the soil (the sole should be placed at a level of 0.5-0.6 meters from the ground).

For your information! At a high level of underwater waters and at an increased depth of laying, the construction of tape bases is not recommended.

The main building and the adjoining annex are considered to have the same foundation. But if the buildings are different in massiveness and the difference exerting pressure on the base is large, when you need to dig a trench of different depths. The entire length of the laying is equipped with ledges (from 30 to 60 cm in height) with braided corners that connect all parts of the structure.

Overview of the soil for laying foundations

1. Clay. It has a bad ability to swell, which is why it can push out the strip foundation during freezing. This is especially dangerous when high rates groundwater. To lay the tape, a depth below the water level is used.

Advice! For loamy soils, which contain 10-30% clay, the pile-belt version of the base.

1. Sandy. Coarse and medium-grained particles let water pass well, allowing it to seep through. However, sand with a dusty or fine-grained structure retains water. In this case, the laying can be carried out to the level of freezing. Sandy soil is always accompanied by deep shrinkage, therefore it will be correct to install a high base.

Advice! If water still affects the structure, it is recommended to install a drainage system to pump out the liquid.

1. Cartilaginous. Contains gravel, large stones and cartilage. Calculations that need to be made: load on the base and the level of groundwater.
2. Rocky. Reliable soil: neither swells nor shrinks. If the soil does not allow digging, the base can be built on the surface.

The depth of the bookmark and the factors that affect it

The higher the location of the sole of the structure, the less waste will be on concrete mix and pouring. The factors that affect the deepening of the base are the relief of the territory, the sensitivity of the structure and the durability of the structure.

The top layer of the soil most often lends itself to changes: it is strongly compressed or changes properties under the influence of weather conditions. Such areas involve removing the top layer of soil, and deepening the base to a stable load-bearing soil, regardless of the depth of its location.

Some owners believe that laying a strip foundation below the freezing level will help get rid of problems associated with the reliability of the structure. Do not forget that this method will not protect the soil from heaving under the influence of frost (especially if these are light buildings). Even if the frozen layer does not have a particular effect on the sole, the walls of the structure are under its influence. To reduce the influence, the following methods are used:

• the side surface of the base is equipped with a sliding layer using a material with a low coefficient of friction;
• the structure is poured in the form of a trapezoid, which tapers upward;
• the soil near the base is equipped with screens that are combined with installations to prevent waterlogging (storm sewers);
• the sinuses of the foundations are covered with non-porous soil.

Before starting work on creating the foundation, it is important to decide what depth will be suitable so that the bearing layer can ensure a uniform settlement of the structure.

Reducing the depth of the foundation

In order to reduce the cost of creating a strip foundation , carry out activities that are aimed at reducing the laying of the foundation.

1. Replace heaving soil to the ungainly. First, you need to dig a pit below the level of soil freezing, which exceeds the design dimensions of the base. Then everything is covered with sand and tamped. The sand has good bearing capacity and does not allow moisture to seep through.
2. Installation of a blind area. Protection against freezing and waterlogging. The blind area is a platform made of concrete with a slope of 10 o. The size of the blind area depends on the type of soil and the overhang of the roof. Subsidence soils involve the use of a one meter wide site.
3. To lower the water table, the construction site is equipped with cuvettes. The installation operates according to the drainage principle. If the site is constantly under the influence of waters, it is equipped with a solid drainage system.
4. To protect the soil from freezing under the blind area of ​​the base, polystyrene foam plates are laid.
5. The basis of a small wooden house can go deep to a freezing level of shallow depth. The foundation must be well reinforced and must not reach groundwater.

The base must be covered with sand or gravel. The leveling of uneven soil and the distribution of the load depends on what kind of bedding you use, which prevents the building from skewing.

Thermal insulation of the base

To protect against freezing of the soil, shallow structures are thermally insulated. Insulation prevents cold from penetrating through the concrete layer to areas below the foundation foot.

For thermal insulation, extruded polystyrene foam is used, which does not decompose under the influence of moisture. The greater the thickness, the better the thermal insulation. 2.5 cm of expanded polystyrene has a resistance of 1.2 meters of soil. But it is necessary to lay high-quality horizontal and vertical insulation. This will prevent freezing and swelling of the soil under the foundation.

The main thing is that all the necessary calculations are carried out before laying the base, this is the only way to build a stable and reliable structure.

At the stage of designing a foundation for a steam room, the most difficult moment is the correct calculation and laying of the foundation. But, if you can somehow figure it out with its type and design on your own, based on the budgetary possibilities and the popularity of a particular type in a certain area, then what is the correct depth of laying the foundation is still a question.

Why are foundations buried in the ground at all? Yes, because several forces always act on the foundation of any house: the gravity of the structure itself, the movements of soil invisible to the eye, landslides and precipitation. That is why it is so important to put the bath on a really solid and solid foundation, thus transferring all the calculated loads to it. And how to correctly calculate this depth, the article will tell.

Foundation depth: dispelling myths

Yes, it seems the simplest solution is to bury the same bath deeper, and it will last a hundred years. In fact, this is not so, and today there are many myths among builders about the depth of the foundation.

The deeper the better?

Even among fairly experienced architects, the myth is widespread that the deeper the foundation, the stronger it is. Of course, you can understand the customer's desire to save money, as well as the foreman who is trying to convey to the fact that with the foundation "at random" - will not work. But to bury deeper does not mean that it will be stronger.

So, the depth of the zero level is determined by many parameters - and it is better to entrust this issue to specialists. Engineering and geological surveys are being done, the type of soil is being investigated, the level of groundwater and its freezing are measured. A lot is also decided by the constructive feature of the building: the number of floors, superstructures, wall material - and the bathhouse in this parameter is just less demanding on the power of the base than a residential building. More details about determining the depth of the foundation can be found in a small interesting book by V.S. Sazhin "Do not bury the foundations deep".

Does depth really always "save"?

But it is far from always necessary to strive to make the foundation deeper if the soil is restless - in fact, there are methods of how to compact and make any soil more solid. And therefore, if the bathhouse is not built at all massive, there is no point, as the builders like to say, “to bury money in the ground”.

So, first you need to study the problem well. For example, if water is often visible on the surface or close to it, competent drainage around the foundation will save. Indeed, it is pointless to strengthen the foundation in this case by increasing the support - the zero level will continue to "walk", and a lot of money will be spent on such a method. There really is a lot of depth here.

But if landslides are observed along the perimeter, the foundation is undermined and even somewhere it begins to sag - it is not it that needs to be strengthened, but the soil. So, for sandy soil, silicatization is good - the soil around the foundation is watered with a mixture of liquid glass and water, one to one, and the resulting wet sand is tamped well. Or they use chemical reagents: small-diameter wells are drilled, and special resin compositions are pumped into them. Durable and inexpensive, and for soft soils - what you need.

Determine the depth using the formula

Here is the standard formula for calculating the depth of the foundation:

Hp = mtmHн, where:

• Hн - depth of soil freezing,
• mt - 0.7-1, the coefficient of influence of the building heat on soil freezing at the outer walls,
• m - 1.1, coefficient of working conditions.

Soil type, temperature and other parameters

So, how to correctly calculate the depth at which the bath should be laid?

Average temperature of the region

Many today, of course, rely on average calculations and fill the foundations 90 cm deep, but experienced builders always insure themselves against a cold winter and reach 1.10 m and no less! Moreover, frosts in Russia are certainly not uncommon. Why, even since Soviet times, the foundation has been laid to a depth of 110 cm - so even in frosty winters, the heaving of the soil cannot disturb anything.

Do we heat the basement?

Unheated structures are laid 10% deeper than the level of soil freezing depth, and heated ones - 20-30% higher. Another point: under the inner walls of the bath, the foundation can be deepened less - it is allowed building codes... But at least 40 cm is important!

The depth of soil freezing

So, in all areas - their own characteristics of the soil, its density and water saturation. Ask the owners of neighboring buildings for such characteristics. But note that if there is a body of water nearby, the winter soil swelling may be much larger than expected. How to find out the standard depth of soil freezing in your area? Use this card here:

Soil properties

What is Seasonal Soil Heave? This is water underground, which freezes in winter, increases in volume (remember school physics) and pushes out what is in this soil. In the spring, it melts and sinks the ground again.

For example, according to official information, on the territory of the Moscow Region, 80% of soils are heaving. These are clays, loams and sandy loams, and all this puffs up a lot in the seasons. On peat soil, there is no need to talk about depth at all: the only possible foundation here is a floating slab.

No less important for determining the required depth of the strip and any other foundation is water saturation: if it is clay and it is heaving, then the deepening of the foundation will have to be made significant. In an extreme case, it is better then to use a stove - for a small bathhouse, that is what you need.

In general, the ideal condition for any foundation is when the groundwater is above the depth of soil freezing. Indeed, when they intersect, groundwater freezes and "swells" the soil, and unevenly, which leads to a distortion of the foundation. And these are cracks and even worse. Because the strength of the seasonal swelling of the soil is 10-15 t / m2, not sickly, right?

Shallow foundations - a benefit or a smart calculation?

And, finally, when determining the depth of the foundation, you need to focus not so much on the type of soil, but on the array of walls and their material. So, profiled beams and logs, from which the Russian bath is built most often, is a flexible and elastic material. After all, a tree is a fibrous structure, and then it works great for deformation, and quite easily survives any movement of the foundation. That is why it is recommended to build a steam room from a log house on a tape shallow foundation only 50 cm deep is enough. A frame bath can have the same base - after all, all its elements are connected by corners, and therefore, you also do not need to worry about cracks and deformations.

Of course, shallow foundations are most often erected in order to save money on the construction of a bath: earthworks little, and the coarse sand used replaces the soil and helps to reduce the degree of deformation. Such foundations can move imperceptibly to the eye, but massive buildings from this can completely collapse. After all, such wall material as brick and stone will not tolerate vibrations and stretches. Both the stone and the brick are fragile, and therefore, regardless of the weight of such a bath, the foundation for it is necessary, as they say, unshakable - one that would not tilt by a millimeter. Otherwise, the walls in the first year will "please" with not small, rapidly growing cracks.

And even after such information, you find it difficult to calculate correctly to what depth you need to dig the foundation for your bath? Welcome to the section ""!

One of the main conditions for determining the depth of foundations on heaving soil is the depth of its freezing. In our country, seasonal soil freezing can reach a depth of 2.5 meters or more. In buildings without basements, the cost of foundations of such a height is unreasonably high, so many people have questions: is it possible to install a foundation above the freezing depth and can the depth of soil freezing be reduced?

There are answers to these questions. Yes, foundations can be installed on freezing ground. These are foundations in the form of monolithic reinforced slabs or reinforced strip foundations on a deep underlying layer of non-porous soil. In this section, we will not consider them, this is a separate large topic. The depth of soil freezing can also be influenced. This is what this article will be about.

Impact of air temperature on soil

The whole process will be considered in the Celsius scale, taking 0 ° С as the reference point.

Imagine that there is a steel ball on the ground with a temperature equal to that of the ambient air. Let us represent the temperature, which the ball will spread to the ground, in the form of vectors (Fig. 16).

Fig. 16. Temperature effect on the ground

Thus, during the winter, the ball will spread a negative temperature to the ground and freeze the ground around itself in a hemisphere on a scale that repeats the contour of the ball. The more cold days there are in winter, the further into the ground the frozen hemisphere will spread. Since winter is not eternal, one day the hemisphere will reach its maximum and will not increase any more. The maximum depth at which the soil turns from plastic to solid is called the depth of soil freezing.

In the spring, the ball heats up and begins to melt the frozen soil underneath. That is, the same process takes place as during freezing, only the temperature vector changes its sign from minus to plus. If there are few warm days, then the soil will not have time to melt to the full depth to which it is frozen. Such soil is called permafrost. We will not consider it now. Further, we are only interested in the soil that completely warms up on summer days.

We examined the process of soil freezing from the action of one ball, in fact, billions of such conventional balls lie on the ground and act on it, forming a frozen or thawed field underneath. If you place any building structure on this field, it will cause an anomaly in it (Fig. 17). The perturbation of the frozen soil field will be different and depend on the thermal regime of the object placed on it. When placing an unheated building, the soil under the building will freeze to a shallower depth, since the temperature in the building will still be higher than in an open field. If the building is heated, then the soil under it will not freeze at all or it will freeze slightly as it will be heated by the building. Therefore, the thermal regime of the building is taken into account regulatory documents(Table 10) and affects the depth of the foundations.

rice. 17-1. Freezing of soil from exposure to negative temperatures
rice. 17-2. Freezing of the soil when an unheated structure is located on it
rice. 17-3. Freezing of soil when a heated structure is located on it

Reducing the negative impact of frozen soil

Construction rules (SP 22.13330.2011) define the freezing depth “equal to the average of the annual maximum depths of seasonal freezing of soils (according to observations for a period of at least 10 years) on an open horizontal site, bare from snow, at a groundwater level located below the depth of the seasonal freezing of soils. "

In this definition, every phrase is important:

• "Average of the annual", that is, the depth of freezing can be greater than or less than the specified value;
• “An open area, bare from snow,” means that under the snow the depth of freezing of the soil will be less (the thicker the snow, the less freezing);
• "With underground waters below the freezing depth", that is, dry soil is examined, if it is wet, the freezing depth will increase.

It is not in the building rules, but everyone knows that the compacted soil becomes more heat-conducting due to compaction and freezes deeper.

Thus, based only on the definition Building Regulations we see several ways to reduce the depth of freezing. The area around the building structure must be covered with snow, not compacted or damp. Ideally, this should be a plowed field and then the soil on it will definitely not freeze to the standard depth even in the most severe winter. But in reality, everything looks a little different. There are access roads to the house, snow from which is removed if possible, and the autumn rainwater from the roof is diverted not far from the house.

The greatest danger to the foundation is represented by temperature vectors located in a strip around the building with a width equal to the depth of soil freezing. If they are removed or somehow reduced, then the foundation can be installed above the depth of soil freezing (Fig. 18).

rice. 18. Schematic diagram of reducing the depth of freezing

Decrease negative impacts from freezing the soil in at least two ways:

1. changes in the physical and mechanical properties of the soil;
2. thermal insulation of the soil.

This is the most simple ways available to the amateur developer.

Changes in the physical and mechanical properties of soil

From the previous pages of this site topic, we know that different soils have different properties. Some of them, when frozen, do not change their structure, others increase in volume and push out the foundation, breaking it in different planes. Let us call such soils frost-susceptible and immune.

Fig. 20. Soils susceptible and resistant to frost

Frost-resistant soils consist of rock fragments (coarse sands, gravel and pebble soils). They also need to replace heaving soils around the perimeter of the building, in whole or by mixing with the old soil removed during the development of the foundation pit. To reduce the effect of atmospheric water on the properties of soils, it is diverted from the foundation. This is done in two ways. Surface rain and melt water is removed by means of a blind area around the building with slopes from 5 to 10%. Water can be diverted along the terrain or into a special drainage ditch filled with coarse-grained soil with a top layer designed in the form of beautiful paths. In construction areas with high snow and frequent rainfall, water seeping to the foundation is diverted from the foundation by means of underground drainage. Perforated pipes are laid around the building in a layer of coarse-grained drainage soil, covered with geotextiles to avoid siltation of the pipes and covered with drainage fine-grained soil. Further, pipes drain water from the foundation along the slope of the terrain or discharge water into drainage wells buried at a distance from barrels covered with stones. The soil around the foundation will not retain water, which means it will not swell in frost (Fig. 19).

Fig. 20. Water drainage schemes from the foundation

The suction of groundwater into the body of foundations and basement screeds is interrupted by the installation of coating and gluing waterproofing, as well as by the device of bedding from fine-grained drainage soils. Due to the relatively large distances (by molecular standards) between the particles, such a bedding cannot retain water in itself, and even more so it cannot suck its top and moisten the bottom of the foundation. Capillary suction can also be stopped by spreading a plastic film under the foundation (Fig. 21).

Fig. 21. Cutting off capillary suction

Thermal insulation of soil

If the replacement and drainage of soils around the house involves a large amount of earthwork in which we affect the thermal conductivity of the soil by simply replacing one type of soil with another, then the thermal insulation of the soil assumes leaving the same soil with a decrease in its thermal conductivity. This is done by installing thermal insulation. I have already said more than once on other pages of the site and will repeat again that the common term "insulation" is used incorrectly. Correct name material - thermal insulation. It is a partition between two materials that interrupts the flow of heat. Thermal insulation retains heat if the material it covers was warm or retains cold if the material was initially cold.

rice. 22. Insulated blind area

Laying a strip of thermal insulation along the perimeter of the building with a width equal to the freezing depth will weaken the flow of negative temperatures penetrating into the soil layer and it will freeze to a shallower depth. On such soil, it will be possible to install a foundation of a lower height (Fig. 22). Structurally, soil insulation is combined with a blind area and is called an insulated blind area. To prevent frost from passing to the base of the foundation through its body, the cold bridge is interrupted by thermal insulation of the basement base (Fig. 23).

rice. 23. Thermal insulation of the base

If you come across drawings showing thermal insulation along the outer vertical wall of the foundation, then the basement is insulated, not the ground. Such insulation retains heat in the basement, while the warmth of the house does not warm up the soil, and the depth of its freezing does not change. That is, the thermal insulation of the foundation walls has nothing to do with the thermal insulation of the ground. They are different Constructive decisions solving different problems.

Laying a strip of thermal insulation around the house can be done at the level of the basement sole and combined with the thermal insulation of the basement (Fig. 24). In this case, two tasks are solved simultaneously: basement insulation and thermal insulation of the soil. The strip of thermal insulation here will be narrower than on the surface of the soil and will depend on the depth of immersion of the foundation.

Fig. 24. Basement and ground insulation

Insulated blind area is best used for buildings without a basement, and recessed thermal insulation for buildings with a basement.

Strip foundation - reinforced concrete structure with rectangular shape cross section. This type of building base is used for buildings made of various materials with a density of more than 1000-1300 kg / m 3. Its use is determined by the severity of the floors, the presence of a basement, and other factors.

It is not recommended to lay a strip foundation on deep-freezing and highly weathered soils.

It is generally accepted that the foundations of the main building and the adjacent extension are laid at the same depth. But if the difference in the loads of buildings on the foundations is large, the depth of their laying may be different. In this case, along the entire length of the foundation, ledges with oblique corners are made, connecting the different-level parts of the structure. The height of the ledges should be from 300 to 600 mm, the angle does not matter.

Back to the table of contents

Factors affecting the depth of the foundation

The higher it is located, the less it will take concrete mix for its filling and, accordingly, financial costs. But sometimes it is unacceptable to save on this. The depth of the foundation of the structure depends on three main factors: the depth of soil freezing, the proximity of groundwater and the type of soil at the construction site.

Other factors that determine the degree of foundation deepening include the planned durability of the building (building class), the sensitivity of the house structures to uneven precipitation, and the relief of the site. Other characteristics of the object related to specific conditions are also of decisive importance.

Often the upper layers of the soil have strong compressibility and the ability to change their properties depending on weather conditions. The foundation in such areas should be deepened on stable bearing soils, no matter how deep they are.

According to the effect on the strength of the base, soils are divided into several groups:

• rocks, coarse rocks with sand, gravelly sands of large and medium size;
• fine and dusty sands;
• sandy loam;
• loams, clays, coarse rocks with clay filler.

There is an opinion that by deepening the foundation below the freezing layer, we solve everything possible problems with structural stability. But this method does not guarantee protection from the effects of frost heaving of the soil, especially for light buildings. If the pressure of the freezing layer on the base of the foundation is excluded, its effect on the walls of the structure is preserved. You can reduce this influence in the following ways:

• a sliding layer is created on the side surface of the base from a material with a low coefficient of friction (construction film, coating or welded waterproofing, roofing material);
• the foundation is poured in a trapezoidal shape with a narrowing upward;
• the soil near the foundation is protected by means of screens combined with devices from waterlogging ( storm sewer drainage);
• the sinuses of the foundation are filled up.

The primary task in the design of the foundation is to determine the depth at which the bearing layer, together with the underlying layers, would ensure a uniform settlement of the structure, not exceeding the maximum permissible rate.

Back to the table of contents

Determination of the depth of the foundation

To calculate the depth of laying the foundation of the building, simple studies of the soil of the site and the calculation of significant parameters will be required.

Using the standard indicator, the depth of soil freezing on the site is calculated taking into account the heating mode of the building according to the formula: Df = k × Dfn, where:

• Dfn - standard freezing depth;
• Df is the estimated freezing depth;
• Kn is a coefficient that takes into account the heating mode of the building (SNiP 2.02.01-83).

The type of soil can be determined by kneading it in the palm of your hand and rolling it up in the form of a cord. Then try to shape the sample into a ring and notice its plasticity:

• if the ring remains intact, the soil is clayey;
• if it breaks down into fragments, it is loam;
• ring, crumbling when folding - the soil consists of sandy loam.

If determining the type of soil is difficult, it is better to contact a specialist.

Then it is necessary to determine what is in the place where the strip foundation will be laid. A well is drilled to a depth of 2.5-3 m. A plastic or metal pipe is lowered into it so that soil does not crumble into the well. The water level is measured at different times of the year. Measurements are taken to determine if the groundwater rises above 2 m to the depth of soil freezing.

Using the data obtained (estimated freezing depth, type of soil, groundwater level) and table 2 of SNiP 2.02.01-83, the required one is determined.

If the groundwater level is more than 2 m below the soil freezing depth, the strip foundation is laid to a depth that depends on the composition of the soil:

• gravelly, medium and coarse sands - 0.5 m;
• sandy loam and fine sands - not less than 0.5 m;
• clays, loams, coarse soils - not less than 0.5 Df.

When the groundwater is closer than 2 m from the depth of soil freezing (Df), the foundation is laid to a depth of at least Df.

Back to the table of contents

Ways to reduce the required foundation depth

To reduce the cost of laying the foundation to a great depth, measures are taken to reduce the impact of heaving soil on the foundation of the future structure.

The most radical way is to replace heaving soil with non-heaving soil. To do this, a pit is dug, in size exceeding the design parameters of the foundation to a depth below the freezing level. Instead of the selected soil, sand is poured and tamped. The sand has good bearing capacity and does not retain moisture in the structure. This method is the most reliable, but requires a large amount of earthwork.

Reduces the depth of freezing and waterlogging of the soil equipment blind area. They are concrete platforms with a slope of about 10 °. The width of the pads depends on the type of soil and the size of the roof overhang. On collapsible soils, the blind area is about a meter wide.

To lower the groundwater level under the construction site, ditches are arranged with water drainage along the slope of the relief. Such structures are effective for drainage during showers and melting snow. For areas where the groundwater level is constantly elevated, solid drainage systems are built.

There is another way that reduces the depth of soil freezing. It is relatively cheap and effective. It consists in laying polystyrene foam plates under the blind area of ​​the foundation. When using slabs up to 5 cm thick, soil freezing is reduced to a depth of 30 cm.

When erecting a non-massive wooden (frame, timber) house, you can save on deepening the foundation by installing it directly into the freezing layer at a shallow depth. But such a foundation should be well reinforced and laid above the groundwater level. The base united along the perimeter of the building into a single rigid frame structure redistributes uneven loads.

When the soil swells in one of the sections under the foundation, the structure does not crack, but rises, supporting the weight of the structure. At the same time, the plane of the base is preserved and deformations in the structures of the house do not occur. For the foundation, sand and gravel must be backfilled. The use of bedding allows you to smooth out the unevenness of the soil heaving, and the reinforced concrete frame distributes the loads along the perimeter, preventing skewing of the structures.

When choosing a site for construction, attention is paid to the physical properties of soils in the first place.

If the soil is bulk, alluvial, peat or vegetative, the construction of a building on this site should be abandoned.

They are absolutely unsuitable for foundations. The highest building properties of soils are in those areas where the soil has long and tightly packed, the content of coarse sand and clay is high.

Physical properties of soils for construction

What are the differences in the physical properties of soils such as sand and clay?

First of all, the main building properties of these soils are as follows. Pure sands have a negligible bond, and clays have significant cohesion. Sands are not plastic, clays are plastic. Sands are compressed almost immediately after the application of force, while clays under the action of an external load are compressed very slowly. At that time, the degree of compressibility of the sands is negligible, the clays are compressed strongly.

What is called a continent, and what should be the qualities of this soil for the construction of foundations?

Any soil capable of serving as a natural basis for the construction of the necessary structure on it is called a continent. Required from the mainland: sufficient strength; low and uniform compressibility; indestructibility; sufficient power; non-weathering. Sufficient strength is determined by the ratio between the weight of the structure per 1 cm of the base area and the pressure permissible for the same area of ​​the given soil. You should also take into account the nature of the load and the depth of the foundation.

What does “light - heavy” house mean?

Heavy is a house on the construction site of which the tangential heaving forces capable of acting on the lateral surface of the foundations buried below the calculated freezing depth are less than the weight of the house. Light is a house on the site of which the tangential heaving forces are greater than the weight of the house. From these definitions it follows that one and the same house can be light or heavy, depending on: on the climatic zone where it is being built; on the degree of heaving of soils; from the thermal regime of the house; from design features basement of the house. For example, an unheated house in the Moscow region may be classified as heavy, and on construction sites in Novosibirsk, with the same soil characteristics, but where the standard freezing depth is 2.2 m and the total heaving forces are greater, it is classified as light houses. To obtain indicators for other regions of Russia, the given parameter for the Moscow region must be divided by 1.4 and multiplied by the standard freezing depth of the region under consideration. Then the estimated freezing depth of the base of an unheated house for Novosibirsk region will be 1.54 × 2.2-1.4 = 2.42 m.

What soil for the foundation of the house is better

What soils are better for the foundation of a future building?

The best soils for foundations are rocky solid and layered, as well as densely packed, rocky clastic, sandy coarse-grained and dense clayey. Vegetable soil, peat, as well as all kinds of alluvial and bulk soils are completely unsuitable.

How reliable is sandy soil in central Russia?

The strength of sandy substrates increases with the size of the sand particles. Slight deformations under load are experienced by sands of medium size. Watering has almost no effect on the strength of coarse and medium-sized sands. Fine sands, with an increase in humidity, noticeably lose in this indicator. However, the most reliable are foundations composed of coarse-grained soils, in which most of the mass falls on particles with a diameter of more than 2 mm; if there are less than 50% of such particles, the soil is sandy. Their load-bearing capacity is not adversely affected by the presence of water or sand aggregate.

Why is it impossible to build foundations on sandy loam, loam, loess-like soils and peat?

Dusty-clayey soils, depending on the content of clay particles, are divided into sandy loam (3-10%), loam (10-30%) and clay (more than 30%). They are all unstable. mechanical performance determined by porosity and moisture. With the increase of the latter, load bearing capacity of such soils is reduced.

The construction of foundations on silty soils is associated with great difficulties, since such soils have significant porosity and anisotropy.

Loess and loess-like soils in a dry state are quite stable due to the presence of strong structural bonds. However, when moistened, these connections are broken, and under load such soil subsides.

It is a mixture of clay or sandy soils with plant residues, characterized by slow sediment development, high compressibility and anisotropy. In addition, peat often contains environments that are aggressive towards the materials of which the underground structures of a building are made.

The depth of soil freezing in the Moscow region and how to reduce it

Houses can be regularly heated in winter and unheated (occasionally heated or with a delayed period of regular heating).

How does this affect the estimated depth of soil freezing in the Moscow region during the construction of buildings?

In unheated houses, the estimated freezing depth of soils increases in comparison with the standard by 1.1 times. In the Moscow Region, the depth of soil freezing is considered to be 1.6 m. If the houses are heated, then the calculated freezing depth is less than or equal to the normative one (depending on the design features of the basement part and the temperature in the house).

For example, at a temperature in a basement house of at least + 15 ° C and the installation of insulated floors along the basement floor, the calculated depth of soil freezing at the external foundations is 1.1 m, at a temperature of at least + 10 ° C - 1.26 m, at a temperature of 0 ... + 5 ° C - 1.4 m. In a heated house with a warm basement or technical underground at a temperature of at least + 15 ° C, the estimated freezing depth of soils near the outer walls of the basement or foundations will be 0.7 m.

Does the soil freeze evenly around the perimeter of the house?

During the winter period, more snow can be deposited on one side of the house than on the other. Where there is more snow, there is less freezing and swelling. At the porch, garage and between them, if they live in the house, the snow is removed along the paths regularly, and if they do not live - periodically. In these places, the freezing of the soil can be greatest. In heated houses with ground floor below there may be a furnace, a sauna. In places where they are located, the adjacent soil may not freeze at all. Under the inner foundations of unheated houses, the soil can freeze to a greater depth than under the outer foundations in the presence of snow. Under the internal foundations in heated houses, the soil may not freeze at all. If the heated houses have adjoining, and, then the freezing under them is much greater than under the outer foundations of the heated part of the house.

What should be the foundation if the soil freezes unevenly?

In light houses, the requirements for the spatial rigidity of the foundations are increased. The higher the degree of heaving of soils, the big demands are presented to the spatial rigidity and strength of foundations. Here, prefabricated foundations with low stiffness characteristics are unsuitable for use. In medium- and highly-weathered soils, it is necessary to install prefabricated monolithic or monolithic reinforced concrete strip foundations in the form of a single spatial, rigid frame with the inclusion of all foundations, including internal ones. Such a frame, together with an anti-heaving cushion, eliminates the unevenness of heaving deformations.

How to reduce the depth of soil freezing if, for one reason or another, the construction of a house is scheduled for winter?

How to defrost soil?

There are two ways to thaw frozen ground: using solar heat or water heat; combustion of solid, liquid or gaseous fuels. The cheapest is the combustion of solid fuel (firewood), followed by filling the fires with sawdust. Under the air cover, firewood and sawdust smolder for days, "letting go" the heat down and warming the earth in depth. When developing frozen soils, percussion machines are used - jackhammers. Trenches worked out in winter should be backfilled immediately.