Foundation pillows are called special supports designed to stabilize the soil under various kinds of buildings and structures. Such elements are an indispensable part of the construction of the foundations of both urban high-rise buildings and private houses. In addition to the stabilizing effect, such pillows also have a protective. If available, the base of the house does not come into contact with groundwater, and therefore, is not subject to destruction. The sizes of foundation pillows may have different. The same applies to their physical and mechanical characteristics.
Main varieties
During the construction of residential and industrial buildings, pillows can be used:
Both of these varieties are laid under the foundations quite often. The advantage of the first type of pillows is low cost, good shock absorbing properties and ease of arrangement.
Concrete structures of this variety are, of course, more expensive and more difficult to install. However, such pillows give the base of the building more stability, making it more reliable and more durable. Such foundation cushions for strip foundations may have different sizes .
Characteristics of sand and gravel pillows
The shock-absorbing layers of this type are usually equipped only under the foundations of low-rise private country houses. Pillows of this variety are placed both under the slab and under the tape base. Such a stabilizing layer is also provided under the supports of columnar foundations.
The simplest and cheapest kind of substrate foundations of houses is sand. To equip it, however, it is only possible:
Cushioned cushions are more dense. Pour them from the material of different fractions. Previously, under such pillows, a small layer of river sand is applied to the bottom of the trench or foundation pit.
Requirements for the arrangement of sand and gravel pillows
Substrate this type of substrate under the foundations of country houses in compliance with the following standards:
the thickness of the sand stabilizing pad should not be less than 30 and more than 80 cm;
the thickness of the leveling layer of sand under the crushed stone cushion should be equal to 15 cm;
the thickness of the rubble pillow itself should be at least 25 cm.
The dimensions of the foundation pillows of this type in most cases are equal to the area of ββthe tape itself or the base plate of the house or the cross-section of the support pillars.
It is believed that if the soil on the site is weak, it is better to equip a combined crushed stone-sand substrate under the foundation of the house. The ratio of materials when filling trenches in this case is defined as 60% to 40%. In any case, pillows made of bulk materials should be carefully compacted during installation. For reliability, this operation is recommended using a vibrating plate.
Concrete structures
This type of pillow is mounted mainly under heavy high-rise buildings and structures. Most often, reinforced concrete structures are used to give strength to the foundations and stabilize them. Such pillows have greater strength and, consequently, service life. Reinforced concrete cushions are enclosed during the construction of high-rise buildings, of course, only under strip foundations.
When assembling the foundations of houses, both stabilized structures cast in place and prefabricated ones can be used. Both that, and other options of substrates are considered rather reliable.
Concrete Pad Pouring Requirements
This procedure is performed using standard technology. That is, a pillow is poured under the foundation as follows:
at the bottom of the trenches, a leveling sand cushion is pre-arranged with tamping water;
formwork and reinforcement cage are installed in the trench;
the pillow is poured with concrete mixture.
When arranging such a stabilizing structure, it is necessary to comply with the following SNiP standards:
The size of the foundation pillows of this type exceeds the sole area of ββthe very base of the house. According to the regulations, the width of the stabilizing reinforced concrete structure must be 15 cm more than the same indicator of the foundation sole.
Ready-made reinforced concrete foundation pillows: dimensions in accordance with GOST
The pluses of such substrates are primarily increased strength and high installation speed. The only drawback of pillows of this type is the complexity of transportation and the need to use special equipment during installation. Such substrates are mounted under jellied, as well as prefabricated strip foundations.
In the manufacture of reinforced concrete structures at enterprises without fail, among other things, certain standards are observed. Regulates the sizes of the foundation pillows GOST 13580-85. According to this document, such structures may have a height of 300 or 500 mm.
The width of products of this type varies in the range of 800-3200 mm (in increments of 200 mm). The length of reinforced concrete pillows depends on their width. You can determine this indicator for standard-size products using special tables. For plates of different widths, this indicator is 780, 1180, 2380 and 2980 mm (in different variations).
Types of bearing capacity
Fundamental pillows FL sizes according to GOST 13580-85, therefore, may have different. But there is another indicator, taking into account which the selection of such products during the construction of houses can be made.
Pillows of this type can be made from different materials and according to different technologies. Accordingly, their bearing capacity may be different. In this regard, all reinforced concrete finished foundation pillows are classified into 4 large groups. To determine how durable such a block is, you can mark it. The higher the class of the product, the greater the bearing capacity it differs.
How are marked: transcript
The purpose of a reinforced concrete slab of this type as a foundation pillow itself can be determined by the PL designation. Regulates the labeling of such products by GOST. FL 16.24-3-P.
According to the designations provided by the manufacturer, you can find out, among other things, the dimensions of the foundation blocks-pillows. The decoding of such products as follows:
the first two digits after "FL" - the width of the product (for example, 16 - 1.6 m);
the second two digits are the length of the pillow;
the next digit is the load bearing class (1, 2, 3 or 4).
If the letter P is additionally indicated in the plate marking, then it is made of concrete with low permeability. Such products may be used including on wet soils.
Mounting technology
In terms of bearing capacity and size, the PL base cushions can thus vary significantly. But in any case, when installing such structures, certain technologies must be followed.
Blocks of strip foundations themselves are marked as FB. According to the regulations, in the construction of buildings and structures it is supposed to use PL plates made using the same building materials as the FB.
Reinforced concrete foundation pillows are installed as follows:
marking is carried out on the site and a trench is excavated;
the bottom of the trench is rammed using special equipment;
waterproofing material is laid;
a leveling sand-gravel pillow is poured at the bottom of the trench;
the bottom substrate is also carefully compacted;
FL plates are delivered to the construction site;
with the help of a crane, they are mounted in a trench;
PL reinforcement is performed;
with dressing, the blocks of the foundation itself are installed;
the walls of the pillow and foundation are waterproofed;
backfilling of trenches is carried out.
When installing blocks of pillows, builders without fail use a level. After all, the upper plane of the finished foundation must be absolutely horizontal.