Foundation heights. Height reference of buildings (landing of buildings on the terrain)
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. Constructors design organization developing construction drawings, determine the depth of the foundation and the dimensions of the sole, calculate the foundation for strength, 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.
The elevation mark is the height of a point in comparison with the conditional plane, the height of which is taken 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 pump sole should be at floor level, i.e. at the zero mark, and the foundation surface should be 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.
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. one hundred | ||
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 |
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 strip foundation can be monolithic or prefabricated-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.
Accurate 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 soLecture 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.
- 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.
Consider the height reference of buildings on 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,
Topic 5. GEODETIC SUPPORT
CONSTRUCTION OF THE UNDERGROUND PART OF BUILDINGS
AND FACILITIES
DEVICE OF THE PIT AND DETERMINATION OF THE VOLUME
SOIL
When arranging pits, the following basic operations are performed: laying out the contours of the pit, installing cast-offs, sight lines, monitoring the excavation of the pit, cleaning the bottom and slopes, transferring axes and heights to the pit, executive surveys of the open pit.
Before laying out the foundation pit, according to the layout drawing, the dimensions of the reserve of the outer edge of the foundation base and the depth of its laying are established. The reserve is necessary to prevent the slope of the pit from collapsing and to install the formwork. The size of the reserve depends on the depth of the pit (at a depth of 2-3 m, it is taken as 20 cm).
From the main axes of the building, fixed on the ground or cast-off, the boundary of the inner contour of the pit is broken, taking into account the accepted margin of the outer edge of the foundation base. From it, the boundary of the outer contour (upper edge) of the pit is broken, taking into account the steepness of the slope.
The boundary of the outer contour of the pit is fixed on the ground with stakes every 5-10 m, between which a cord is pulled or a groove is made for 1-2 bayonets of a shovel to indicate the boundary of opening the pit.
To lay out trenches for strip foundations, from the main axes of the building to the right and left, values \u200b\u200bare deposited, which in total make up the width of the base of the foundation.
Breakdown of pits for columnar foundations is carried out along the main and auxiliary axes, in the alignment of which the centers of the foundations are outlined. From the centers, the contour of the pit is broken.
Control over the progress of excavation and bringing the depth of the pit to the design mark of its bottom is carried out using sight lines or a level.
Permanent sights in the form of horizontal bars are nailed to the cast-off posts at the same height (usually 1 m above the zero mark). On the bar sign the mark of the sight.
To determine whether the soil is selected from the pit to the design mark, a portable (running) sight in the form of a rail is installed at its bottom. A line is marked on the rail with paint, the distance to which from the heel of the rail is equal to the difference between the marks of the edge of the bar of the permanent sight and the design bottom of the pit. If the line on the running sight is higher than the cord stretched between the nearest planks, then the soil from the pit has not yet been selected to the design mark.
To determine the actual elevation of the bottom of the pit using a level, first set the leveling rod to a benchmark with a known elevation. H p and take a reading on the rail but. Then the rail is transferred to the bottom of the pit and a reading is taken b. The excess between the benchmark and the bottom point of the pit will be h= but- b. By adding the excess with its sign to the mark of the benchmark, they get the mark of the bottom of the pit at this point:
Excavation in pits and trenches is completed with a shortage of 10 - 20 cm to the design mark, after which the bottom of the pit is manually cleaned according to the results of leveling it in squares. The tops of the squares are fixed with stakes, the upper sections of which (beacons) are located at the level of the design mark, and they are stripped. After cleaning the slopes of the pit with the help of squares with plumb lines or guides, an additional survey of the pit is carried out. Deviations from the design dimensions in the width and length of the pit should not exceed 30 cm. The deviation of the bottom of the pit for foundations from the design ones is allowed no more than ± 5 cm, provided that these deviations do not exceed the thickness of the fill underlying layer. Permissible mean square measurement errors when arranging pits: linear - 1/1000; angular - 45 "and high-rise - 10 mm.
Rice. 36. The scheme of transferring the axes of the foundation
into the pit with theodolite
1 - theodolite; 2 - leading sign; 3 - cast-off; 4 - roulette; 5 - axial wire; 6 - axial risk; 7 - movable mark
The completion of the excavation device is confirmed by executive geodetic documentation: an act of readiness of the excavation, a scheme for a planned high-altitude survey of the excavation, a cartogram for calculating the volume of earth masses.
The transfer of the axes to the pit is carried out using a theodolite from the leading points (Fig. 36), fixing the axes, or plumb lines from the intersection points of the axes, fixed by wires stretched along the cast-off (Fig. 37).
Fig.37. Scheme of transferring center axes
into the pit with plumb lines:
1 - cast-off; 2 - risks of axes; 3 - axial wire; 4 - beacon blocks; 5 - mooring; 6 - plumb
Rice. 38. Scheme of transferring the design mark to the bottom of a deep pit
In the pit, the axles are fixed with temporary signs at the bottom or on the slopes.
The transfer of heights to the pit is carried out by a level directly to the bottom or along the slopes. Marks are transferred to deep pits using a suspended tape measure and two levels (Fig. 38).
From Fig. 28 it can be seen that the mark of the bottom of the pit H to = H rp + but- L-b,
where H rp - benchmark mark;
L- the length of the tape between the lines of sight of the levels:
L = t - p.
Determining the volume of soil during the development of the pit is necessary for the operational control of the actual volume earthworks. The volume of soil depends on the size of the pit in terms of its depth, the laying of slopes and construction. For pits with different slopes (slope steepness) (Fig. 39, a), you can use the formula for calculating the volume of the obelisk:
where V- the volume of the pit;
h- depth of the pit;
but - long side of the pit at the bottom;
but 1 - the long side of the pit is at the top;
b- the short side of the pit is at the bottom;
b 1 - the short side of the pit is at the top.
Rice. 39. Pit scheme:
a - with different laying of slopes; b - complex configuration
For pits with the same slopes, a formula is used to determine the volume of soil, using which there is no need to measure the upper dimensions of the pit in terms of:
where h a b - the volume of the pit, excluding slopes;
h(a+ b) - the volume of the pit above the slopes, excluding angles;
from - horizontal projection of slopes;
The volume of the pit above the slopes in the corners.
For ease of calculation, this formula can be reduced to the following form:
V= h[ ab +(a + b) with + ]. (84)
For pits of complex configuration (Fig. 29, b) and with the same slopes, the formula is used
where S- area of the lower base of the pit;
R - perimeter of the lower base of the pit:
P =(a + b + d+ e+ g+...).
For small pits with slopes with their area below 100 m 2 and depth up to 4 m (in order to simplify the calculation), the volume of soil is determined as the product of the area in the average section of the pit and its depth:
V= S cf∙ h .(86)
For pits with vertical walls and fasteners, the volume And soil is determined by the formula
V= S·h.(87)
Operational control of the volume of earthworks using this method allows to reduce the complexity of this process.
DEVICE AND CONSTRUCTION OF FOUNDATIONS
Initial data for execution geodetic works for the arrangement of foundations, there are schemes of the axes of buildings and structures with distances between them and reference to foundation structures, plans and sections of foundations and pits for supporting structures, technological equipment, marks of bearing surfaces of foundations and foundations.
The accuracy of the foundation device is characterized by the displacement of the axes of the elements relative to the mounting axes and the displacement of the planes and supporting surfaces from the design height.
As well as general principles and methods of geodetic marking work during the device various types foundations have their own characteristics.
Installation of prefabricated strip foundations (Fig. 40) begins with the installation of corner pillows and blocks along a wire stretched over the axial nails of the cast-off.
Rice. 40. Scheme of breakdown of prefabricated strip foundations:
5 - theodolite; 6 - axial risks
With a significant length of the building (more than three sections), a number of intermediate (beacon) blocks are installed with an interval of 15-20 m. The remaining blocks are laid along the pier, fixed on the outer edge of the previously mounted blocks. Axes fixing the inner faces of the foundation blocks are transferred to the laid foundation pads, and the blocks are mounted according to the risks of these axes. The correct installation of the blocks in the plan is checked (Fig. 41) from plumb lines with an axial wire, lateral leveling or hanging with a theodolite, and vertically and horizontally - with a plumb line and level.
Simultaneously with the geodetic control of the installation of foundation blocks, the inputs to the building of underground utilities are laid out using longitudinal and transverse building axes, for which the necessary holes are left in the masonry of the blocks, taking into account the design mark of the input.
Rice. 41. Foundation installation control:
a - in the way of the lead string; b - theodolite;
c - lateral leveling method
After the installation of the first row of blocks is completed, leveling is carried out. Deviations in the position of the upper surface of the blocks from the horizon are corrected when arranging a horizontal seam (bed) for the next row of blocks.
After the installation of the foundation blocks is completed, their location is checked with the drawing up of an executive diagram, which shows the displacement of the blocks from the axes and fluctuations in the actual marks relative to the design ones. Deviation of blocks from the axis and installation height is allowed up to 10 mm. The height setting is controlled using a level. Based on the results of the executive survey, the installation horizon is leveled for laying floor slabs above the basement or technical underground. The device of monolithic strip foundations (Fig. 42) begins with the erection of formwork. Reinforcement is installed in it, after which it is filled with concrete to the required mark. The internal edges of the formwork coincide with the edges of the foundation.
Rice. 42. Formwork for a monolithic strip foundation:
1 - slats; 2 - level; 3 - cast-off; 4 - axial wires;
5 - formwork box
The formwork is installed in the design position from the building axes fixed on the cast-off with the help of a theodolite or plumb lines. Height control is carried out on unhardened concrete with a level. The rail is placed on a sheet of plywood or tin so that its heel does not sink into concrete. The upper edge of the foundation is marked on the formwork with nails or paint. The mark is transferred using a level from the nearest benchmark with an accuracy of 3-5 mm. The position of the formwork is controlled from the center axes. Its deviation from the design position in the plan should not exceed 5-10 mm.
The verticality of the formwork installation is checked by a plumb line, the height position - by a level.
After filling the formwork with concrete, it is leveled with a wooden bar. For an accurate result, metal pins are driven into the unhardened concrete, fixing their top at the design mark. In such concrete, metal plates (brackets) can be laid to fix axes and marks on them. Performing this operation from the inside of the foundation is especially necessary if technological equipment will be installed in the basement in the future.
Formwork for a monolithic foundation for columns is made of boxes, which are installed in the planned position according to the risks on their ribs or along the rails. To do this, on the upper edges of the shields, the middle of the box is marked and slats are nailed over it. The edges of the rails should be located along the axes of the box. From the wires stretched along the axes of the column above the pit, plumb lines are lowered and the box is moved until both risks or slats nailed to the box touch the plumb line. In this position, the box is firmly fixed. The foundation box for the prefabricated column is usually concreted not to the design mark, but somewhat lower, so that later it will be possible to pour and level the concrete to the design mark applied to the formwork. At the end of concreting, using a theodolite, the longitudinal and transverse axes of the columns are applied to the upper plane of the foundation, marking them with risks on concrete or on pre-laid metal brackets or plates. Then a high-altitude executive survey of the foundations is carried out. The rail is placed at the corners of the foundation rectangle and in its center.
Reinforced concrete columns are installed on a glass-type foundation. Plates for glasses are laid along the axes on the cast-off. The correct installation of the plates is checked with a theodolite, and in height - with a level. The horizontalness of the base is checked using a level or building level, the layout of the base is checked using a rail laid on the bases in different directions. When constructing a glass, the concreting of its bottom is not brought to the design mark by 2-3 cm in order to fill the bottom with cement mortar after leveling to the desired mark. The bottom of the recesses of the foundations (glasses) is leveled in all corners and in the middle. According to the notches on the foundations, the distance between the axes is checked, their displacements and the distance from the axes to the walls of the foundation cups are determined.
An additional work in the construction of a foundation for metal columns is the installation of anchor bolts using special conductors firmly attached to the foundation formwork (Fig. 43).
Rice. 43. Installation diagram of anchor bolts:
a - under metal columns; 6 - control of anchor bolts according to
height; 1 - template; 2 - anchor bolts with nuts; 3 - fastening bolts
bottom; 4 - template board; 5 - metal ruler
Rice. 44. Preparation of the foundation for the installation of steel columns
but- up to the design mark; b- followed by concrete pouring;
1 - channels; 2 - design plane; 3 - anchor bolts; 4 - anchor of an anchor bolt;
5 - pouring concrete after the column is installed
For precise installation of anchor bolts, a special template is made for each typical group of anchor devices. The simplest template for columns with a small load can be made from durable wooden boards, fixedly fastened together and with formwork. Under columns with a significant load, instead of wooden templates, steel ones are made.
The holes for the template anchor bolts should not differ in plan from the holes on the column shoe. Axes are drawn on the templates corresponding to the axes on the formwork. Axes of templates and formwork must be aligned.
High-altitude installation of bolts to the design mark is carried out using leveling. Approximately installed bolts are leveled from the original benchmark. Then, using a millimeter ruler, determine the difference between the design and actual marks. Deviations in plan and height of anchor bolts from their design position should not exceed 5 mm. After the final installation of the bolts, they are fixed together by welding with pieces of reinforcement and the foundation is concreted.
After the concrete has hardened, the template is removed, the bolts are leveled, and according to the marks obtained at their base, nails are driven into the semi-hardened concrete to the design mark, along which the surface of the shoe resting on the columns is grouted. Height measurements when installing nails are performed with a metal ruler.
Then make a control survey. It is performed with a theodolite, which is installed on the leading signs of two mutually perpendicular axes. A reading is taken along the vertical thread of the theodolite on a metal ruler with millimeter divisions applied to the center of the anchor bolt.
Pile foundations are constructed in accordance with the plan of the axes and the pile field. Piles are arranged in one or more rows or combined into groups - bushes.
The centers of the piles are marked from the fixed main axes using a theodolite and tape measure or from axial wires. The theodolite is installed above the alignment axial signs, oriented along the alignment of the axes and the design distances to the centers of the piles are laid in this direction. The centers of the piles can be determined using plumb lines suspended at the intersection of the axial wires.
With a bush arrangement of piles, the center of the bush is marked in the described way and the centers of the piles are broken from it. It is convenient to make a detailed breakdown from the central points with a special template if the size of the bush does not exceed 3 m.
For piles located not on the axes and remote from the center but of the bush, their position from the axes is determined by the method of perpendiculars using a tape measure and eker.
To control the amount of immersion, each pile is marked by meters in the direction from the tip to the head, and the design depth of immersion of the piles is marked with the letters PG. The verticality of the immersion of the piles is ensured by setting the guide boom of the pile driver in a vertical position. When using vibrating pile drivers, the verticality of the guide boom is checked with theodolites, and when using pile drivers with hammers and push pilers, with heavy plumb lines.
If, during the immersion, a deviation of the piles from the vertical position is noticed, then the work is suspended to correct the position of the boom and the pile.
At the end of pile driving, marks are made on their heads for cutting piles for head supports and grillages. After cutting the piles, an as-built survey is performed to determine the deviations of the centers of the tops of the piles from the design position and their marks. In cases where the position of the driven piles differs from the standard (more than 0.2 of the pile section), duplicate piles are driven in.
grillages on pile foundations, on which the supporting structures are based, are built prefabricated or monolithic. In both cases, the horizontality of the upper surface of the grillage is controlled.
Pile foundations. Places for driving piles are determined from the points of intersection of the axes. The axes, fixed outside the contour of the pit, are transferred first to the upper edge, and then to its bottom. The sequence of laying out pile driving sites depends on the type of pile fields, the accepted pile driving schemes, and the directions of movement of pile driving installations (installation for driving or driving piles).
With a single-row arrangement of piles (Fig. 45, but) all the main (overall) axles are transferred to the bottom of the pit (A, B, 1, X etc.). Intermediate axes are divided between the overall ones at the bottom of the pit and are chosen in such a way that the distance between them is no more than the length of the tape measure used. Overall and intermediate axles are fixed on construction benches 2 . .
Rice. 45. Breakdown of piling sites with a single row arrangement (but)
and construction bench (b):
1 - anchorage point of the axis on the edge of the excavation, 2 - construction benches, 3 - signs of fixing the alignments of the axes, 4 - pile driving points, 5 - vertical and horizontal rods, 6 - movable mark
Between moving marks b benches (Fig. 45, b) installed in the alignments of the axes of the same name, they pull the mooring cord (fishing line) and transfer the intersection points of the longitudinal and transverse axes of the building to the bottom of the pit. The intersection points are marked on the upper end of the stake driven into the level with the ground. In the alignment of one of the axes, a tape measure is pulled and, when the piles are located on the axis, stakes are hammered in at the design distances between the piles, fixing the places 4 of their immersion. When the piles are located outside the alignments of the axes at a distance of no more than 4 m, the places of immersion of the piles are broken, postponing the design distances between the piles from the tape measure stretched along the alignment. At the points obtained, perpendiculars are restored “by eye” and the places of immersion of piles are determined with a second tape measure.
With a cluster arrangement of piles, the breakdown sequence changes somewhat. At the bottom of the pit, after fixing the main axes on the construction benches, the centers of the bushes are determined. Distances are measured with two tape measures from the alignment formed by the fishing line. A long tape measure is pulled along one axis between the movable marks of construction benches. A fishing line is pulled along the marks of the other axis. At the intersection of the tape measure and fishing line, the center of the bush is determined. Keeping the direction of the alignment of the axes, with the help of a second tape measure or meter, the location of each pile in the bush is determined.
When the piles are located at a distance of more than 4 m from the axes, parallel to the axes taken out in nature, the lines are broken with an offset from the alignment of the axes by an amount equal to the distance from the pile to the previously taken out axes. Places for piling are determined both in single-row and cluster arrangement.
To control the immersion depth on each pile, divisions are applied every 1 m from the tip to the head. Meter segments are marked with bright risks with meters digitized, and the design immersion depth is marked with the letters PG.
The verticality of the pile immersion is ensured by installing the guide boom of the pile driver in a vertical position. When using trackless pile drivers based on tractors and crawler cranes, the soil is planned under one mark. The rail heads for rail pile drivers are brought to the same marks. The plumbness of the guide boom of vibratory pile drivers is checked with theodolites, and pile drivers with hammers and push pilers are checked with heavy plumb lines. The weight of the plumb line (in any case, more than 5 kg) depends on the length of the piles to be driven and the strength of the wind. If during immersion the pile deviates from the vertical position, the work is suspended and the position of the boom and pile is corrected.
On the heads of the installed piles, the design mark of their felling (cutting) is taken out. After cutting off the heads, an executive survey of the position of the piles in the plan is performed. Shooting is carried out from the alignments of the lines parallel to the offset from the axes. These alignments are obtained by moving the movable mark along the crossbar of the construction bench by an amount equal to the diameter of the pile plus 100 mm. When piles are located outside the alignments of the axes, the shooting is carried out directly from the alignments of the axes. If measurements are made up to the faces of the piles, the offset of their centers is calculated as follows.
Rice. 46. Executive survey of the pile field
For example, the design binding of the center of the pile to axis 1 (Fig. 46) is 1250 mm, 1 to the axis B- 265 mm. Displacement of the pile head from the design position along the axis B calculated from the results of measurements: 1250 - (1436 + 1040) / 2 = 12 mm; 1250 - (1448 + 1047) / 2 = 2.5 mm. The average displacement is (12 + 2.5)/2 = 7 mm, and along axis 1 on both sides of the pile, the displacement will be 265 - (265 + 65)/2 = 0 mm.
The numbers on the as-built survey diagram indicate the displacement of the pile head from the design position. The place where the number is written shows the direction of the offset.
Deviations during pile driving should not exceed 0.2 ... 0.4 of the side or diameter of the pile.
Theodolite is installed above the alignment of the 7th axis and brought into working position. The pipe is oriented along axis 1. When the piles are located on the alignments of the axes, the pipe is directed sequentially to the piles located at least 3 m apart, and the alignment of the axis is marked on the heads with a pencil. When the piles are located outside the alignments of the axes at a distance of no more than 4 m, a leveling rod 3 is horizontally applied to the heads of the piles, which are also located at least 3 m along the alignments. .
Rice. 47. Transferring axles to piles:
1 - sign of fixing the alignment of the axis, 2 - sighting rays, 3 - rail, 4 - face of the pile, 5 - theodolite, 6 - stake, 7 - alignment of the axis
The perpendicularity of the rail to the alignment of the axis and its horizontalness are determined "by eye". The heel of the rail with a count of 0 is leaned against the edge of the pile, perpendicular to the alignment. By horizontally moving the rail, a reading is introduced into the bisector of the grid of threads of the theodolite pipe but. Reference value but along the rail is equal to the design binding of the pile to the axis.
The observer checks the horizontal position of the rail and its perpendicularity to the alignment using the grid of telescope threads. In this case, the rail is applied to the head (node II ) at an angle of 45° to the vertical plane passing through the face 4 of the pile. All axes passing along the dimensions of the building, as well as longitudinal and transverse axes, which are located at a distance equal to the length of the tape measure used or less, are transferred to the piles.
On device monolithic foundations using a pile foundation, the breakdown consists in marking the longitudinal and transverse axes of buildings on the pile heads.
The axes are transferred to the piles sequentially from the signs 1 fixing their alignments 4 to the edge of the pit (node 1 ). The axes on the edge of the pit are fixed on the upper end of wooden stakes 6 with a diameter of 10 cm, a length of 25 cm. The stakes are hammered no closer than 1 m from the top edge of the pit. The alignment of 7 axes is marked (with a pencil or other marking means). Then the theodolite is installed sequentially over the transferred points and its pipe is oriented along the alignments of the axes of the same name.
According to the described method, all overall axes, as well as longitudinal and transverse axes, located at a distance equal to the length of the tape measure used or less, are transferred to the piles.
Further, all longitudinal and transverse axes are marked on the pile heads. When piles are located at a distance of more than 4 m from the alignment of the axes, lines parallel to the axes are transferred to nature, with an offset from the axes by an amount equal to the distance of the pile from the axis plus 200 ... 50 mm. Axes on piles are marked with pencil lines.
Frame reinforcement and formwork are marked in plan from the axes placed on the pile heads. To do this, geometric leveling transfers the height marks to the heads of the svans. 3 marks of the top of concreting and control marks separated from the marks of concreting by 100 mm. They are signed +0.1 m.
The correct installation of the formwork is checked by measuring the distance from the axial marks on the pile heads to the inner edge of the formwork with a rail (meter) 2 and determining the thickness of the protective layer 5 of concrete. The verticality of the formwork is controlled by plumb lines along the outer edges, and the value of the concrete protective layer in the lower section is checked “by eye”.
When arranging foundations in a sliding formwork, in addition to the previously described layout work, the formwork is aligned. To do this, the formwork walls are installed with an inclination, which ensures an increase in the distance between them downwards (the taper is within 10 ... 14 mm, if another taper is not established by the project). The slope of the walls is checked by a plumb line. Additionally, the distance between the inner surfaces of the wall sheathing is also found, which is determined in the middle of their height (this distance is equal to the design wall thickness).
During the concreting process, the installed formwork is continuously monitored. If the formwork is deformed or displaced, the concreting is suspended and the formwork elements are returned to the design position. In this case, measurements are performed in the same way as when installing the formwork.
Upon completion of concreting, an executive survey of the foundations is carried out in plan and in height. For shooting in plan, the axes are again transferred to the upper and side faces of the foundations. Measurements are taken from the transferred axes and their deviations are determined by the difference between the measured and design distances.
An example of recording the results of an executive survey of monolithic foundations is shown in fig. 49. The numbers with a plus or minus sign show the deviation of the top or bottom of the foundations from the design marks (plus - excess in comparison with the design, minus - underestimation). Numbers without signs indicate the amount of expansion or narrowing of the foundations; at the same time, if the figure is written on the inside of the foundation outline, then it is narrowed, if on the outside of the outline, then the foundation is expanded.
Rice. 48. Breakdown of axes and marks for the installation of reinforcement and alignment of the formwork
(reinforcement conditionally not shown):
Prefabricated foundations. Foundations for foundations are checked for height by leveling. With a pit depth of up to 3 m, marks on its bottom are transferred directly from the edge. In this case, the rear rail is installed on one of the benchmarks, and the front rail is installed on the rack of the construction bench at the bottom of the pit or on a fixed stake. The level is set very low so that the sighting axis is located at a height of no more than 1.2 m from the ground. With a pit depth of more than 3 m, the marks are transferred to its bottom in several stages. The leveling course is laid along the route for the exit of vehicles from the bottom of the pit (along the ramp), and in its absence, a slope is used to install the rail.
Rice. 49. Executive survey of foundations
Marks at the bottom of the pit are fixed on temporary benchmarks laid at least two per construction site. The marks of the bases of the foundations are determined for each foundation in several places. Separate prefabricated foundations are broken in this way (Fig. 50). Axes are brought to the bottom of the pit for the installation of corner and lighthouse foundation blocks or pillows. The alignments of the axes of the building are sequentially transferred to the upper edge (bench 3), and then to the bottom of the pit. With the help of theodolite 1, all the overall longitudinal and transverse axes, as well as axes passing through the installation grips or queues, are transferred to the bottom of the pit construction works. The correctness of the transfer of the axes is controlled by measuring the length of the diagonals.
Rice. 50. Transferring axes to foundation blocks:
1 - theodolite, 2 - sign of fixing the alignment of the axis, 3 - construction benches,
4,6 - tape measure, 5 - mooring cord, 7 - movable mark
Corner and lighthouse foundation blocks can be installed without transferring the axles to the bottom of the pit and using the alignment of the axles on the upper edge or construction benches. In this case, the foundations being laid are oriented with two theodolites, and the intermediate foundation blocks, setting aside the design distances between them with a tape measure 4 . If shoes are installed on the foundations for columns or foundations are mounted in several rows in height, the axes are broken using the first row of laid foundations as the base. In this case, all the markings of the alignments of the axes and the lines of their intersections are marked.
If the corner and intermediate blocks are installed along the theodolite and level, then there is no need to lay out the axes on the construction benches. In this case, a mooring cord 5 is used, which is pulled along construction benches 3, corner and lighthouse foundations at a distance of 20 ... 30 mm (to the edge of the foundation being mounted).
Prior to the installation of foundations, installation risks are marked with a meter on their faces. With a symmetrical binding of the foundations to the axes, the installation risk is applied in the middle of the foundation, with an asymmetric binding, the installation risks are applied by measuring the values of the bindings from the same edges on all foundations.
When installing shoes under columns (Fig. 51), reference risks 1 applied, based on the size of the openings of the glasses. The hole is marked in accordance with the binding to it or the axes of the column. With the help of a ruler, a fishing line and a plumb line, this marking is transferred to the outer edges at the point of contact between the installed foundation and the mounted shoe. Orientation risks 3 on the foundations and installation risks 2 on the shoes are combined by eye.
Rice. 51. Combination of risks when installing the foundation under the column:
1.3 - reference risks, 2 - installation risks
Elevation marks during the installation of columns in the glasses of foundations are checked by geometric leveling and leveled by placing calibrated gaskets and installing embedded fixing devices. Gaskets are calibrated in thickness according to high-altitude as-built survey data.
Strip prefabricated foundations are broken in the same way as separate ones. To fix the position of the axes, you can use the mounting wire 1 (Fig. 52), stretched between the construction benches 2. In this case, the transfer of the axes to the pit is carried out using plumb lines 3. Thus, corner and lighthouse foundations are installed.
Rice. 52. Scheme of breakdown of strip prefabricated foundations
Intermediate foundations are arranged between corner and lighthouses using a mooring cord. If the foundations are mounted in several rows in height, then the subsequent breakdown of the axes and the removal of marks is carried out using the first row of laid foundations as the base.
Upon completion of the erection of prefabricated foundations, an executive survey is performed. To do this, axes are again transferred to all elements of the foundations. When performing shooting of shoes for columns, the height marks are determined by the bottom of the glasses.
When constructing a foundation by a contracting construction organization, the quality of the erected foundation is documented by an act signed by representatives construction organization And technical supervision customer or developer.
The executive scheme drawn up by the construction organization is attached to the act. The executive scheme is drawn up on the basis of the executive geodetic survey of the foundation structures, during which the actual planned and altitude position, as well as the verticality of the structural elements of the foundation and its dimensions or deviations from the design dimensions are determined. Separately, as-built drawings of underground engineering networks should be submitted with reference to the input of sewerage, water supply, etc. into the house.
The control of the position of the foundation structures in the plan and its geometric parameters is carried out directly by measuring the distances with a steel tape measure. The control of the height position of the supporting planes (the horizontality of the upper cut of the foundation) is performed by geometric leveling. The perpendicularity of the longitudinal and transverse axes (walls) of the foundation is determined by theodolite. The verticality of the walls (pillars) of the foundation is verified by a plumb line.
Rice. 53. Geodetic executive scheme of the foundation:
Explanations: 1 - the figure in the circle indicates the serial number of the location for determining the mark of the lighthouse; 2 - figure with a minus sign indicates the thickness of the leveling layer of the solution; The thickness of the solution between the points is determined by interpolation
The executive scheme is a foundation plan (Fig. 53), on which its actual dimensions and height deviations are applied. According to the results of the check, the permissible limit deviations are determined (see SNiP 3.03.01-87, table. 12). They must not exceed the following values:
deviations of the foundation walls from the vertical - 20 mm;
displacement of the foundation from the center axes (marks) - 12 mm;
deviations of marks of beacons relative to the mounting horizon - ± 5 mm.
For the mark of the mounting horizon, as a rule, take the average value of the transferred marks or the mark of the highest point (for the convenience of leveling the horizon under one mark). The surface of the foundation under the mounting horizon is leveled with a cement-sand mortar according to pre-installed beacons, the thickness and location of which are transferred to nature from the executive scheme.
Drawing up an executive scheme of the foundation
If the construction of the foundation is not carried out by a contracting construction company, but by the developer himself or hired workers, then the executive scheme can be performed without the use of geodetic instruments (theodolite and level). It is enough to have a plumb line, a building level, a steel tape measure and a water level (see Fig. 7). First, the highest point on the foundation surface is determined, which is taken as a conditional zero mark of the mounting horizon, then this mark is transferred using a water level to other places pre-marked and numbered on the plan and foundation. According to the ruler attached to the level, the value (thickness of the beacon solution) is determined in millimeters to align the mounting horizon. Beacons for leveling the mounting horizon can be installed immediately in the course of working with the water level. To do this, the laid solution is leveled with a trowel until it is aligned with the water level of the water level.
The geometric dimensions of the foundation are measured with a tape measure, rectangularity - with diagonal measurements, and verticality - with a plumb line. The horizontal level of the leveling layer of the mortar laid on the beacons is determined by the building level. The location of the entrance to the house of underground engineering networks is marked on the drawing (section of the foundation), determining the entry points by two perpendicular notches with a distance from the top of the foundation, corners of the house, doorway, etc.
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