Height reference of buildings (landing of buildings on the terrain). Geodetic stakeout of the foundation Determination of elevations of the foundation

One of the fundamental works in the construction of a cottage or a country house is the geodetic support of construction. Geodetic works are carried out, starting from the vertical planning of the territory and up to the last sheet of the outer skin of the building. And neglecting the geodetic breakdown of the foundation is an irreparable mistake, which can be very expensive.

Many of us who are engaged in such a responsible business as building our own house or cottage sometimes neglect geodetic services and competent construction support. And the point here is not whether it is independent construction on its own, or an order from a company specializing in the construction of cottages, services for the implementation of construction and installation work.

Both options provide for savings on optional (as it seems to many) geodetic measurements, the lot of which takes place at various state district power plants, nuclear power plants, thermal power plants and other critical production facilities. And here lies the biggest mistake. We build something for ourselves and for our clients, who must be satisfied with the completed order, and therefore not have problems during the further operation of their home.

The foundation starts from the ground

The basis and the most expensive part of the construction is the foundation of the cottage, in which you need to invest a lot of effort. A good insurance for the quality of the work performed is the geodetic breakdown of the foundation, correctly fixed on the territory of the future building.

Geodetic work during the construction of the foundation of a building is divided into several stages:

Sand leveling.
Preliminary breakdown of the boundaries of the foundation.
Formwork installation control.
Planning and high-altitude control of concrete work.

Sand leveling. What goes around comes around.

It is logical that without properly preparing the base, we will not get a high-quality foundation pour that meets the basic requirements of table 5.12 of SP 70.13330.2012 in terms of cross-sectional thickness and other parameters. Therefore, armed with a tripod installed in the working position, a level, screwed to the tripod with a set screw and a rail, we align the base under the foundation.

Important advice! It is obligatory that any geodetic equipment must be verified in a specially certified center for verification of measuring instruments, which is confirmed by a certificate of successful metrological certification issued by one of the many organizations that have in their arsenal the necessary precision equipment for verification.

Alternately placing the rail on the sand within the boundaries of the future foundation, we take readings along the rail with an accuracy of 1 mm. Fortunately, the magnification of the telescope of most levels is 30 times, and even at a great distance it will not be difficult to see each stroke of the staff. The place where the reading was the largest will be the lowest point on the surface against which the sand base needs to be leveled.

Important advice! If the design or working documentation of the building indicates the top of the sand base and the coordinates of the boundaries of the foundation, tied to the local system of coordinates and heights, then it is necessary to obtain from the Federal Service for State Registration, Cadastre and Cartography (Rosreestre) the coordinates and heights of the nearest (relative to the building) geodetic signs (benchmarks). Moreover, at least three such benchmarks are necessary for the correct location of the future building on the ground.

The control of the correctness of the work performed will be the same reading on the rail anywhere in the sandy base. This means that the surface is horizontal. After the base of the foundation is leveled and the accuracy of the work corresponds to the main geometric parameters of Table 6.3 of SP 45.13330.2012, you can proceed to the next stage of work.

Preliminary breakdown of the boundaries of the foundation. Look don't miss!

Columnar, pile or solid monolithic and strip foundations, which are more common for cottages, are laid down by the project - it is not so important. Any foundation has its own characteristic turning points or radial bends that need to be fixed in place. In this work, we will be helped by a tacheometer - a geodetic device that allows you to take out both the design heights and (unlike the level) and design coordinates.

Having set the total station in the working position and carried out the binding of the total station using the resection method (if it is necessary to stake out the foundation in the local system of coordinates and heights), you need to install the mini milestone (usually supplied with the device) in the intended location of any corner of the foundation, and take a reading. Planned coordinates and height displayed on the instrument display will tell you in which direction to move the minipole to find the exact position of one of the corners of the foundation.

Important advice! A mini milestone, in contrast to a large milestone with a massive reflector, will allow you to achieve the necessary accuracy of stakeout of any points, because has the property of flexible height adjustment. In places where the landscape is leveled, the height of the mini-milestone can be several centimeters, which will significantly reduce the error in the deviation of the mini-milestone reflector from the vertical position and increase the accuracy of the geodetic stakeout of any foundation.

In the same way, you can find the position of all the corners of the foundation, and in the case of the presence of radial (semicircular inserts), the following procedures should be performed:

take out in nature the center of the circle of the semicircular insert;
place the zero stroke of the tape measure in this place and stretch the tape measure to a distance equal to the radius of the semicircle of the foundation;
pass with the required frequency from the beginning to the end of the radial insertion and secure these places with stakes.

In the future, having such a detailed breakdown of the semicircular part of the foundation, it is possible to achieve accurate installation of the formwork, as well as the aesthetic beauty of the flooded complex foundation sector! The result of this stage of work is small-diameter reinforcement hammered into the sand preparation, standing vertically relative to the ground.

Formwork installation control - measure seven times…

When constructing the formwork, it is necessary to monitor its verticality relative to the ground. If the height of the foundation is 500 or more millimeters, then the slope of the formwork is not excluded, which means an error in the planned position of the top of the foundation and, most dangerously, a decrease in the strength of the formwork. When pouring, a formwork that is not properly fixed and even at a slight slope may well fall apart and disrupt the concrete work.

Therefore, the control of the verticality of the formwork with a conventional building level can significantly save both money and nerves. Applying a level across the installed formwork board, you can immediately, during installation, level the formwork. It is especially necessary to pay attention to the alignment of the angles of the formwork with the clogged reinforcement (installed in the previous stage) indicating the angles of rotation of the foundation, as well as the straightness of the formwork on each of its sides.

After mounting the formwork in the same way as the previous operation, we check the angles of rotation of the foundation using a tacheometer for compliance with the design position, but already putting the mini-milestone on top of the formwork board. With a quality work done, it is convenient, seeing the rigidly fixed boundaries of the foundation, to lay out the reinforcement and knit the frame.

Planning and high-altitude control of concrete work. Go!

This stage is the final stage and is an indicator of the quality of the previous stages of work. And here you need a surveyor!

Before pouring, it is necessary to install high-altitude beacons with the help of a level or total station, which will show the level of concrete pouring. It is preferable and much more convenient to do this work with a total station, and here's why. Many modern total stations have a laser sight, including which you can see the aiming point without looking through the telescope. All you have to do is point the laser point at the desired side of the formwork and take the reading.

The height that will be displayed on the display will tell you whether to move the laser spot up or down with the instrument's directing screws. Having found the required design height, you can hammer a nail into the place of the laser spot or draw a line with a waterproof marker. As for the center of the foundation, here it is possible to tie short rods to the main reinforcement cage, arranging them so that the top of the rod is at the level of the fill. This will be a good reference for the concrete work crew.

But the most confident and high-quality work of the surveyor during pouring. When leveling concrete as a rule, the geodesist can non-contactly (by pointing the laser pointer of the total station directly at the liquid concrete) control the newly leveled concrete and give valuable guidance on the deviation from the design height of certain sections of the foundation.

1. The value of the correct layout of the foundation

In construction, marking the foundation for a house is the transfer of dimensions and axes of the designed structure from the drawing to the construction site.

With an incorrectly marked foundation, its walls will not form a rectangle, but a rhombus or trapezoid. This may not be visible to the eye, however, when laying the slabs of the first floor already - above the basement, they may fail or hang in one of the corners. This position will be noticeable. It will turn out much worse if there is not enough support area for the plate, and instead of 150 - 200 mm, it will remain 50 or 30 mm. The slab will fall into place, and then, after loading with a screed, flooring, heat and sound insulation and their structural elements, furniture and residents, it can break off part of the wall and ...

It is also problematic to build a roof without right angles. It will be very difficult or impossible to install rafters and mount the roof correctly, for example, laying tiles or slate.

2. Requirements for the site. Georeferencing based on geodesy data (soil types, groundwater)

The site for construction should be, if possible, flat, free from trees and shrubs. It would be nice if it had a slight slope.

The contours of the site must have clear, i.e., points that do not move during the entire construction period, which are marked on the plan. If one of the edges of the site goes to the "red line", then it must be marked on the ground. You can score several stakes on this line.

If possible, several wells should be drilled to determine the characteristics of the soils at the site, the level of groundwater and their chemical composition.

If the groundwater on the site is close to the surface and is located near the design level of the foundation, then it is imperative to arrange drainage, i.e. drainage. In this case, water must be diverted 0.7 - 1 m from the bottom of the foundation.

3. Tools and materials for marking

Markup tools include:

Roulette. Preferably metal, at least 10 m long, preferably 20 m. Fabric is lighter and a little more comfortable, but it sags and accuracy decreases.
Laser level for marking the foundation, its height, horizontality, and other works.
The water level, also known as the flexible level or hydraulic level, is a long flexible tube with transparent glass or plastic sighting tubes at both ends, on which divisions are made exactly every 1 mm and each of them is closed with a cork. This device operates according to Pascal's law for communicating vessels. The length of the flexible tube is 12 meters or more. The tube is filled with water so that it is approximately in the middle of the sighting tubes.
Thin strong rope (twine), cord. You can use thin wire, but it is not very convenient to use.
Markers, pencil, paper, multiplication table, formulas.
Hammer, nails.
Material for the manufacture of cast-offs - wooden stakes - at least 16 pcs. and bars - 8 pcs. Sometimes 8 pieces are used. U-shaped pieces of steel reinforcement that are driven into the ground.

4. Brief description of the laser level

A laser level is one of the devices that belong to a large group of measuring instruments.

The main purpose of the level is to determine the difference in heights of one place on the surface relative to another place and the construction of planes: vertical, horizontal and any intermediate in the form of a line - a trace of a laser beam. In addition, such a device can build point projections - give a point on the surface.

The most commonly used self-leveling cross levels, which build two perpendicular planes - horizontal and vertical. They can be rotated and installed in any direction. The horizontal plane is constantly adjusted by the auto-leveling elements.

The main characteristics of laser leveling are:

measurement accuracy, professional devices give an error of up to 3 mm at 10 m, and household devices up to 0.5 mm at a distance of 1 meter;
measurement range: in household up to 10 m, professional - 30 m or more;
the number of planes to be designed - usually two or more, etc.

But the level is, first of all, a measuring tool.

It will help you well only if you know how to use it correctly.

Having taken it for temporary use, that is, for rent, do not expect it to work on its own.

If you do not know what alignment is, do not rent the device.

Starting work with it, check the accuracy of measurements, whether the settings are knocked down, that is, check all the characteristics described in its passport. All verification operations are in the description for the device.

There are no works on the laying out of the foundation that cannot be carried out without a level. Therefore, the usual water level, properly used, may well replace it. Although a laser level speeds up and simplifies work at a construction site.

5. How the strip foundation works, its advantages

It is called tape because it looks like reinforced concrete tapes laid in a trench dug along the contour of the building. If the soil is crumbling, the laying depth is large, and there are many intermediate walls inside the perimeter of the building, for which it is also necessary to build a foundation, then a foundation pit is torn off, in which all foundation work is carried out.

Structurally, the strip foundation can be monolithic or precast-monolithic. In the latter case, its upper part will look like a monolithic reinforced concrete belt, located along all the walls of the foundation, assembled from separate blocks.

When conducting private construction, trenches for a strip foundation, in order to save money, can be dug manually. In this case, the soil is either removed or scattered over the site, raising its level.

The depth of the strip foundation is usually determined by the level of soil freezing. For the southern regions of Russia, it is slightly more than a meter, in the northern regions and in Siberia - 1.5 - 2 and even more.

Advantages of strip foundations:

simple construction technology;
it is possible to lay a basement or basement floor;
built on solid soils - stone-sand and clay;
they are quite economical;
parameters - width, depth, amount of reinforcement, etc. indicators that affect strength are easily adjustable.

You can build such a foundation under the house with your own hands.

6. Marking axes and angles - placing benchmarks outside the perimeter of the foundation

The starting point of all markings should be a point on the ground, which is precisely “tied” to the site plan. Most often this is a corner point, usually associated with the so-called "red line" - the border of your site and public territory, on which neither you nor anyone else is allowed to build. Crossing the border of your and neighboring area with the "red line" will give such a point. The fence of your site should be located inward from the red line.

Usually the house is located from this fence and from the neighboring fence at distances:

according to sanitary and household standards defined by SNiP 30-02-97, clause 6.7: at least 3 m;
according to fire safety standards SP 42.13330.2011p.7.1: at least 6 m from windows to the walls of a neighbor's house or garage, bathhouse, barn, etc., at least 3 m - from a residential building to the border of a neighboring plot.

Therefore, you need to retreat to the specified distance or further, and you can start marking the foundation with your own hands.

A. Installed on the terrain "red line". If the owner is going to build a house exactly at a normalized distance from the "red line", then it is better to invite a professional land surveyor to mark the future corners of the house. But most often they retreat by 1 - 1.5 m from these restrictions.

Precise orientation to the cardinal points. It is possible at a great distance from the "red line". But usually they are guided by the center line of the street or road.

If you mark the corners of the foundation with pegs, hammering them exactly at the points of the future corners of the house, then when digging a trench, the marking pegs will definitely fall into the trench.

Therefore, the marking of the site for the foundation begins with the fact that outside the trench or pit, or rather, outside the excavator's work area, wooden support frames are installed. They are called cast-off boards or beams, and simply - cast-offs. Some "experts" call them "benches". Cords or wire are pulled over them. The intersections of the cords will give the necessary marking points, but not on the ground, but “hanging” in the air. These "points" are later transferred to the ground or to the formwork.

On the upper bar of the cast-off, three or five carnation marks are hammered:

in the center - axial mark, for the axis of the foundation wall;
to the right and left of the axial - marks the width of the foundation wall;
even further - the width of the pillow under the foundation.

Step 1. Marking the initial side.

We start from the side that is closer to the "red line".

At 1 - 1.5 m outward from any corner we hammer in two cast-offs. We stretch the axial cord. With the help of a water level, set the upper part of the cast-off bars at a height of "0". Stepping back 1 - 1.5 m, we drive the first peg into the ground - we make the starting point. From it, with a plumb line, we “raise” the point on the cord. We measure the length of the wall along the axes on the cord and make a mark on it. We lower the point to the ground and hammer in the second peg. Between the pegs - the axis of the first wall.

Step 2. Marking the side perpendicular to the initial one.

Using the Pythagorean theorem and, knowing the lengths of the sides of the foundation, we calculate the length of its diagonal (along the axes). On the cast-off of the perpendicular side, on the axial nail, we fasten the end of the cord and pull it onto the opposite cast-off. From the intersection with the axial cord, we measure the length along the axes of the second side and make a mark on the cord of the axis of the second side. On a free piece of cord, we tie knots along the length of the diagonal along the axes. We fix one knot on the mark of the axis of the third side and pull the second knot in the direction of the opposite cast-off of the second side. Aligning the second knot with the mark on the cord of the second side and pulling the cords, we get the first right angle.

Another way to construct a right angle is the "Egyptian triangle" method. On the cord of the first axis, from its intersection with the second axis, we measure 4 meters or a distance that is a multiple of this value. On the cord of the second axis we measure 3 m or a multiple of the distance to the same extent. We make marks on the cords and measure the distance between them with a tape measure. It should be 5 m. Moving the second cord relative to the point of intersection with the first, we achieve the exact value - 5 m. The angle in this case will be straight.

Step 3. We do these operations two more times and get two more right angles.

The last actions should take place in the zone of one point - the virtual corner of the foundation, opposite the first corner. If all measurements were done accurately, and the calculations were accurate, then the last two nodes should match.

Step 4. Checking the squareness of the markup.

From school geometry it is known that both diagonals of a square or rectangle are equal. Therefore, a check is made by measuring the length of both diagonals and comparing them.

A difference of a few centimeters is acceptable. The marking of the foundation axes is completed.

Step 5. Marking the edges of the walls and pillows. We retreat the necessary distances from the axial mark, drive the carnation-marks into the oblong bar and pull the cords already along the borders of the walls.

After checking the correctness of the virtual layout of the entire network in terms of, i.e., in the horizontal plane, it is all removed and excavation can begin with an excavator.

6.1. Permissible errors when marking foundations

Errors usually accumulate. Therefore, you need to start with the highest possible accuracy of the initial markup. The diagonals of the foundation of an ordinary house should differ by no more than 3 - 5 cm. If you managed to get a difference of 2 cm, then this is very good.

If it is 1 - 2 cm, then you know how to make markings and work carefully. If it is 3 - 4 cm - then you are at the limit. If it is 5 cm or more, then you need to check the lengths of all segments and make adjustments up to the last operation. Recheck every corner and all knots. After that, again check the diagonals.

7. Marking to ensure high-altitude leveling of the foundation

Such marking is done with a laser level and applied to the cast-off stakes with a wood marker.

For this, the height of the foundation level, more precisely its upper plane, is calculated. For a prefabricated monolithic foundation, this will be the upper plane of the monolithic belt.

A laser level is installed and a horizontal plane is “beaten off” at the desired height. It will cross all columns of all cast-offs. At the point of contact, you need to put a marker on the label columns.

After the site is ready for placing the foundation, the network of marking cords is restored, and all significant points of this network are transferred using a plumb line down to the bottom of the ditch or pit to mark the area for laying (installing) the pillow and formwork for the walls.

Formwork can be installed.

Questions and answers on the topic

No questions have been asked for the material yet, you have the opportunity to be the first to do so

The initial stage of construction is considered to be surveying the relief and "binding" the building on the ground, that is, determining the distance, elevations and angles in relation to any already existing points (objects) strictly marked on the ground. Such points are usually points created geodetic service almost throughout the entire territory of our country, called the geodetic network.

The relief of the site is a set of irregularities of its surface. To determine the relief of the site, the elevation marks of individual points on its surface are compared with the elevation mark of the ocean surface. In our country, the reference point is considered to be the average level of the Baltic Sea, corresponding to the zero mark of the Kronstadt water current - a copper board built into the abutment of the bridge. To determine the height marks of the building foundation, it is advisable to install a "ground mark" on the site, which can be a piece of a metal pipe hammered into the ground below the calculated freezing point of the soil. So that the soil sign is not damaged during earthmoving, it is placed in an area inaccessible to machinery. The place where the ground

the sign should be clearly visible from the construction area of the building. Until the completion of the construction of the zero cycle, the soil sign must not be sprinkled with soil or cluttered with building materials. For safety, soil signs are protected by a wooden or metal cast-off.

As a soil mark, you can use the top point of the foundation of an existing building or structure that is not demolished during the construction process.

The height marks of the peaks of the topographic map are determined using a special geodetic instrument called a level (Fig. 8). It is mounted on a tripod and fixed by base 1 with three adjusting screws 8. Using these screws, the level is set strictly horizontally (distortions are controlled by hydraulic level 2). The final adjustment of the horizontal position of the telescope 6 with the eyepiece 4 and the front sight 5 is carried out after each turn of the level using a cylindrical level.

The process of determining the elevation of one surface point above another is called leveling. To do this, the level is installed between two points, the difference in elevations of which must be determined (Fig. 9). A leveling rod is installed on these points and, alternately pointing the telescope at them, determine the value indicated by the intersection of the optical grid threads. The difference between the obtained values means the difference in elevations of the desired points. The numerical values of these points are applied to the topographic grid (Fig. 10), after which the volumes of earthworks for the vertical layout of the site are determined.

The volume of earthworks between two adjacent profiles is determined by the formula

where F, and F2 are, respectively, the areas formed between the design line and the line of the earth's surface

Rice. 10. Sample topographic grid

fillet obtained by a geometric method defined for both embankments and cuts;

L - distance between profiles.

The simplest method for determining the volume of earthworks while maintaining balance is to solve the problem using a grid of squares with vertex marks found by horizontal interpolation or leveling. To do this, taking the lowest mark of the top of the square as a conditional zero, determine the excess of all the tops of the squares over this zero

Find the average excess for each square;

where n is the number of squares;

hi, h2, h3 - excesses of the square vertices obtained during the calculation. Knowing the area of a square (P), it is easy to find the volume of an earthen body within each square.

By the sum of the volumes of individual squares, the volume of land of the designed site is determined. Knowing the volume of land and the total area of the land, determine the thickness of an evenly distributed layer

The found value of t makes it possible to determine the design elevation of the horizontal platform

The correct determination of the marks of the territory and the buildings being built on it ensures efficiency and reduces the volume of earthworks, helps to preserve the natural relief, supplementing it with artificial transformations. This issue is especially relevant in areas with complex engineering and geological conditions. Incorrect solution of these problems leads to an increase in earthworks, overspending of building materials, which affects the cost of construction and the architectural appearance of the site.

Lecture on the topic: Engineering organization of the territory of populated areas.
Part 9: Altitude binding of buildings. (planting buildings on the terrain)

Height reference of buildings (landing of buildings on the terrain)

The height of the landing of buildings is determined based on the design marks of the adjacent territory and bordering intra-microdistrict passages.

Buildings and structures on the design relief should not be underflooded.

In the case of lowering the relief towards the building, at a distance of 5 m from the blind area, an artificial tray with a transverse slope of 10 to 25% is arranged.

The transverse slope of the blind area of the building is taken equal to from 5 to 10%.
The minimum longitudinal slope for the building is determined from the drainage conditions - 4-5%.
The maximum longitudinal slope is assigned based on the fact that the difference in the red marks of the corners of buildings should not exceed 1.2m.
The smallest difference in the mark of the finished floor and the blind area is 0.5m, the largest - from 1 to 2m. Thus, the mark of the finished floor is determined by summing the maximum red mark of one of the corners of the building and the value selected according to the project from 0.5 to 2m. With a greater height difference, it is necessary to change the standard design of the building.

With a greater difference in height, it is necessary to change the design of the building (use of stepped-type houses, vertical displacement of individual sections of typical houses) or carry out special measures (terracing of the slope, installation of slopes, retaining walls, etc.).
Consider the height reference of buildings on a specific example (Fig. 15 and 16).

Fig.15. Building Elevation Determination .

1. Determine the marks of the corner of house A (the highest):
164,32 + 0,10 + 5 0,025 = 164,55
2. Determine the marks of the corner of house B: 164.55 + 0.05 = 164.60

3. We determine the marks of the clean floor: 164.60 + 0.85 = 165.45

4. Determine the marks of the angle B: 164.55 - 0.80 \u003d 163.75

5. Determine the angle marks: 163.75 - 0.24 \u003d 163.51 ≈ 163.50

6. Checking the difference along the facade B - D:
164,60 - 163,50 = 1,10 < 1,2 м

along the facade A - B: 164.55 - 163.75 = 0.80< 1,2 м
Along the facade and end,

Foundations for heavy equipment consist of a sole that transfers the pressure of the weight of the equipment and the foundation itself to the ground, as well as the foundation itself and embedded parts for attaching the machine. The size of the sole depends on the weight of the equipment and the nature of the operation of the machine, as well as the properties of the soil. The designers of the design organization that develops construction drawings determine the depth of the foundation and the dimensions of the sole, calculate the strength of the foundation, determine the grade of concrete from which this foundation should be built, and provide all the necessary embedded parts and openings for pipelines of electrical cables, etc.

It is very important to check the dimensions of the foundation. Before starting the installation, builders must transfer the executive scheme of the foundation. The executive scheme is a drawing of the foundation, on which, next to the design dimensions, the actually completed, or, as they are called, executive dimensions are shown. A qualified installer and foreman must be able to understand the executive schemes.

Let's analyze the executive scheme of a simple foundation (Fig. 10). The foundation is designed to accommodate the pump and electric motor, with the motor base located above the pump base. The diagram shows the design dimensions of the foundation (only those dimensions that are relevant for installation are shown) and the actual ones. So that they can be distinguished and compared, the actual dimensions are written above the design ones and are surrounded by a rectangular frame. It is important for the installer to set the height marks of the upper part of the foundation and the position of the bolts according to the executive scheme. In some cases, especially when installing complex machines, it is required to know other dimensions of the foundation.

Fig. 10. Executive scheme of the foundation for a pump with an engine.

An elevation mark is the height of a point in comparison with a conditional plane, the height of which is assumed to be zero. In factory floors, the floor level of the lower floor is usually taken as the zero mark. In the example being analyzed, the floor level is also taken as the zero mark, and all other marks are compared with it.

In FIG. 10 it can be seen that the sole of the pump must be at floor level, i.e. at zero, and the foundation surface is lowered by 30 mm to leave room for the gravy. Therefore, the top plane of the left side of the foundation should be -30. During installation, the pump must be installed on pads 30 mm thick so that it takes the design position.

In order not to obscure the scheme, only the actual linear dimensions (length, width, distance between bolts, etc.) are put down on the drawing itself, and the points for measuring elevations are indicated by numbers and put in a separate table.

Consider, for example, the elevation of the left side, measured at point 5. From the table, we learn that the actual elevation of this point is -38 mm, i.e., the foundation is “underestimated” by 8 mm against the project. This must be taken into account and, in order to properly install the pump, place linings under it with a thickness of not 30 mm, but 38 mm.

In this order, the entire scheme is considered. In this example, almost all dimensions deviate from the design within the limits allowed by the tolerances. Only the height mark of the bolt 9 raises doubts. Apparently, due to careless installation during concreting, the bolt turned out to be 12 mm lower than necessary. This can result in the bolt threads not extending beyond the top end of the nut when fully tightened.

For example, a very simple foundation was taken. Schemes of complex foundations are drawn up and studied in the same sequence. The study of any circuit, complex or simple, must be taken very carefully, this will prevent possible errors in advance. In order for the installer to be able to consciously approach the consideration of the executive scheme, it is necessary to know the permissible deviations in the dimensions of the foundation, in which there are no complications in installation. In table. 2 shows the tolerances for the acceptance of foundations for the installation of equipment.

Table 2. Acceptance tolerances for foundations for equipment installation

Checked size and nature of the deviation	Permissible deviation from the dimensions of the drawing, mm
For concrete foundation:
main dimensions (length, width, etc.)	±30
dimensions of recesses, protrusions and internal cavities	+20 -10
notches, protrusions and internal cavities	±10
elevations of the top surfaces of the foundation associated with the machine	+5 -10
For foundation bolts:	With bolt diameters up to 50 51 - 100 St. 100
height	±5	±8	±10
along the axes	±3	±5	±5
by deviation from the vertical position, mm per 1 lin. m	1	1	1
According to the breakdown of axes (accuracy of punching dies)	±1.0
According to the elevation marks of benchmarks	±0.5