Laying out and securing the axes of small artificial structures. Executive layout of the building axes

GEODETIC WORK IN CIVIL

CONSTRUCTION

PRODUCTION OF ZERO CYCLE WORK

Breakdown of axes of buildings and structures

Buildings and structures consist of individual interconnected geometric elements. This connection is ensured by the relative position of the axes. Laying out a building consists of identifying and fixing axes on the ground. The configuration and dimensions of the building determine the number and type of axes to be transferred to reality.

There are three types of axes of buildings and structures. The main axes are two mutually perpendicular lines, relative to which the building or structure is located symmetrically. The main axes on the general plan are designated by Roman numerals.

The main axes run along the contour of a building or structure, some of them - longitudinal - are designated by letters, and those perpendicular to them - transverse - are designated by numbers. This designation of axes allows us to avoid unambiguity of concepts in the production of alignment and construction work.

Figure 1 - Main and main axes of the building

bot (Fig. 1). For linear structures (roads, pipelines, canals), the main and main longitudinal axes are outlined in the project. If the structure is rounded, then the axes follow its contour.

Auxiliary or alignment axes are used for detailed breakdown of parts and elements of structures. They are designed and laid out most often parallel to the main axes, but can also be located at an angle to them. When laying out, it is enough to secure the main and main axes with four signs, two on each side of the building. Signs must be located at the same distance from the building, in places that ensure their long-term safety and unhindered work, especially during the construction of the zero cycle, and must be fenced off (Fig. 2) from the horizon to subsequent floors. Therefore, the distances to the leading signs should be no less than the full height of the structure, and, if possible, be one and a half heights of the building.

To reduce the number of axis signs, you can paint it on the walls of existing buildings that fall within the alignment of this axis.

In addition to the planned layout on the ground, each building under construction must be provided with at least two working high-rise benchmarks. The mark of the finished floor of the first floor of a building under construction is taken as zero; in the future, all marks below the floor will be negative, and above - positive. The construction zero mark is transferred to working benchmarks using the geometric leveling method.

The installation location of working benchmarks is selected taking into account their ease of use during high-altitude alignment and control work and taking into account their safety for the entire construction period.

After completing the layout of the building or structure, securing the axes and installing working benchmarks, the surveyor and pro-

Figure 2 - Axle layout diagram

The contractor of the construction work draws up an act of transfer and acceptance of the alignment work, attaching a diagram for securing the axes, linear and angular dimensions between the axes, starting points of the geodetic alignment base and other necessary data.

Construction of cast-offs

To carry out detailed alignment work during the construction of the underground part of the building (zero cycle), a cast-off is built. It is a special fence installed along the outer contour of a building under construction at a certain distance from the main axes, to which the main and detailed alignment axes are transferred. The casting ensures high accuracy (1-2 mm) of laying out the axes and transferring them to the pit when constructing foundations. It is designed on the general plan parallel to the contour of the building and so that it does not fall into the area of excavation, installation of construction cranes or storage areas of building structures. Typically, the distance from the wall of a building under construction to the cast-off is 4-8 m, but no closer than 1.5-2 m from the upper edge of the foundation pit.

According to the design, the cast-off can be solid, sparse or folded. In case of continuous demolition along the perimeter of the building, pillars are dug in approximately 2-4 m at the accepted distance. Using a level, marks are made at one level, at a height of 0.5-1.2 m, and edged boards are nailed. In some places for transport to leave, breaks are made (Fig. 3, A).

A sparse cast-off is arranged similarly to a continuous one, but only at the locations of the axes (Fig. 3, b). Casement cast-off (Fig. 39, V) consists of free-standing pillars,

Figure 3 - Types of cast-offs:

A- solid; b - sparse; V- folding

placed in the alignment of all axes of buildings. Each pair of pillars secures a separate axis. All pillars are installed along a line parallel to the axes of the building. The cuts should be at the same height. On terrain with a large slope, the cast-offs are built with ledges.

In the practice of housing construction, inventory casting is widely used. It consists of metal anchors driven into the ground every 3-4 m. Metal racks with couplings are inserted into the holes of the anchors, into which a tubular rod is mounted horizontally. The axles on the rod are fixed with a special movable clamp with a sign indicating the name of the axle.

The relative error of linear measurements when dividing axes according to wear is 1/10,000-

1/25,000. The accuracy of the axes is determined by errors in the non-parallelism of the sides of the cast-off to the longitudinal and transverse axes of structures, deviations of the cast-off from straightness and its non-horizontalness; in order to ensure the specified accuracy of the axes by wear, the influence of each error should not exceed approximately 1/50,000.

The angle of non-parallelism of the cast-off is found from the formula:

It cannot be more than 22". The amount of deviation of the cast-off from the target is calculated as follows.

To perform marking work, the following methods are used: polar and rectangular coordinates, angular, linear and alignment serifs.

Angular notching method used to mark inaccessible points located at a considerable distance from the starting points.

There are direct and reverse corner serifs.

In the direct angular intersection method, the location of the design point on the ground WITH(Fig. 10) are found deposited at the starting points A And IN design angles at 1 and at 2. The basis of the notch is either the specially measured side or the side of the alignment network. Design angles at 1 and at 2 are calculated as the difference between the directional angles of the sides. Directional angles are found from solving the inverse geodetic problem using the design coordinates of the point being determined and the known coordinates of the starting points.

Rice. 10.

The accuracy of the layout using the direct angular intersection method is influenced by errors: the direct intersection itself, the initial data, theodolite centering and sighting targets , fixing the alignment point. During alignment work, centering the theodolite and sighting targets using optical plummets, as well as fixing the set-out point can be performed relatively accurately. Therefore, the main errors that determine the accuracy of the direct angular notching method are the errors of the notching itself and the source data. The total value of these errors can be significant, which will require angular notching with increased accuracy.

The required layout accuracy in this case can be achieved as follows. Having set aside the angles in l and in 2 as accurately as possible, the position of the point is determined in nature WITH. Then, at the reference points, the exact value of the delayed angles is measured using the appropriate number of techniques. For the example given, when using a 2T30 theodolite, at least four steps must be performed. The angle r at the point is also measured WITH. Having distributed the discrepancy in the triangle equally over all three angles, determine the coordinates of the point WITH. Comparing them with the design values, corrections (reductions) are found, according to which in nature they shift (reduce) the approximately offset point WITH. This method is called closed triangle method.

The use of the reverse corner cutting method for staking is also based on the principle of reduction. Approximate position is found on the ground ABOUT" split design point ABOUT(Fig. 11). At this point, a theodolite is installed and angles are measured with the required accuracy to at least three starting points with known coordinates. Using resection formulas, the coordinates of an approximately certain point are calculated and compared with the design values. From the difference in coordinates, the reduction values (angular and linear elements) are calculated and the point is shifted to the design position.

Rice. eleven.

To control the angles at this point, calculate its coordinates again and compare them with the design ones. In case of unacceptable discrepancies, all actions are repeated.

In the linear intersection method, the position of the point to be staked out WITH(see Fig. 10) are determined at the intersection of the design distances S 1 and S 2, laid down from the starting points A And IN. This method is usually used to lay out the axes of building structures in cases where the design distances do not exceed the length of the measuring device.

It is most convenient to carry out the breakdown using two tape measures. From point A on a tape measure the distance S 1 is plotted, and from the point IN on the second roulette - S 2. Moving both roulettes with the zeros aligned with the centers of the points A And IN, at the intersection of the ends of the segments S 1 and S 2, find the position of the point to be determined WITH. geodetic alignment road construction site

Polar coordinate method widely used when laying out the axes of buildings, structures and structures from theodolite or polygonometric points, when these points are located relatively close to the points taken out into nature.

In this method, the position of the determined point WITH(Fig. 12) are found on the ground by deposition from the direction AB design angle b and distance S. Design angle b is found as the difference in directional angles b AB And b AC , calculated as well as the distance S from solving inverse problems using the coordinates of points A, B and C. To control the position of a fixed point WITH can be checked by measuring at the point IN angle in" and comparing it with the value obtained as the difference in directional angles b VA And b Sun " .

Rice. 12.

The error of the actual layout using the polar method depends on the error in constructing the angle b and the error in deposition of the design distance S. The calculation shows that for these conditions, reducing the error in the position of the point set out in nature is possible only with a significant reduction in the error in deposition of the design distance - at least by half.

Methods of leading and leading-linear serifs are widely used for setting out the alignment axes of buildings and structures, as well as the installation axes of structures and technological equipment.

Design point position WITH in the alignment notch method, it is determined at the intersection of two alignments specified between the starting points 1-1" and 2-2" (Fig. 13). The target is usually set with a theodolite, which is centered over the reference point (for example, 1), and the telescope is oriented towards the sighting target, centered on another reference point (in this case 1"). Position of the point WITH fixed in a given alignment.

The mean square error of the alignment intersection depends on the errors in constructing the first and second alignments, as well as the error in fixing the reference points.

Rice. 13. A- alignment serif; b- leading-linear serif

Sliding-linear method allows you to determine the design position of the point to be plotted WITH(see Fig. 13) by plotting the design distance d along the target AB.

Rectangular coordinate method They are used mainly when there is a construction grid on the site or in the workshop of an industrial enterprise, in the coordinate system of which the position of all the main points and axes of the project is specified.

Design point breakdown WITH(Fig. 14) are produced according to the calculated values of the increments of its coordinates D X and D Y from the nearest grid point. Larger increment (in Figure D Y) laid down along the alignment of grid points AB. At the resulting point D install a theodolite and build a right angle from the side of the grid. A smaller increment is laid along the perpendicular and the resulting point is fixed WITH. To control the position of the point WITH can be determined from another point on the construction grid. The scheme of the rectangular coordinates method essentially combines the scheme of the linear and polar methods.

Rice. 14. Layout scheme using rectangular coordinates

The method of polar coordinates is widely used when laying out the axes of buildings, structures and structures from points of theodolite or polygonometric traverses, when these points are located relatively close to the points taken out into nature.

In this method, the position of the determined point WITH(Fig. 16) are found on the ground by deposition from the direction AB design angle β and distances S. Design angle β is found as the difference of directional angles and AB and α A.C., calculated as and distance S from solving inverse problems using point coordinates A, B And WITH. To control the position of a fixed point WITH can be checked by measuring at the point IN corner β ׳ ’ and comparing it with the value obtained as the difference in directional angles a B A And α CA .

Rice. 16. Layout scheme using the polar coordinate method

The mean square error of setting out point C is determined by the formula

The error of the polar splitting itself depends on the error m β constructing an angle β and errors t S deposits of design distance S

. (56)

The influence of source data errors when t A = t B = t A B expressed by the formula

, (57)

and centering errors

. (58)

Formulas (57) and (58) are similar. From these formulas it follows that to reduce the influence of errors in the initial data and centering it is necessary that the angle β and the ratio were minimal, the polar angle would be less than the right angle, and the design distance would be less than the layout basis, i.e. β < 90°, S< b.

For approximate calculations, taking β = 90° and S=b, we get

; , (59)

and for the total error in the position of a point divided by the polar coordinate method,

. (60)

For example, let’s evaluate the accuracy of the design point breakdown With with points of polygonometry moves, for which b= 250 m t AB = 10 mm. Let's accept S=100 m, , β = 45°, m β= 10", e= 1 mm and m f= 1 mm.

The deposition error of the design line will be

mm;

linear value of the error in constructing the design angle -

mm,

quantities t β And ρ expressed in seconds;

influence of source data errors -

From the ratio of the obtained values it is clear that errors of centering and fixation can be neglected. Thus,

The calculation shows that for these conditions, reducing the error in the position of the point set out in nature is possible only with a significant reduction in the error in deposition of the design distance, at least by half.

Rice. 17. Scheme of layout using the design polygon method

If the point to be laid out is located at a considerable distance from the starting point, then it is necessary to postpone the design angles and distances several times using the polar method, laying out the design course (Fig. 17). If there is direct visibility from the point WITH per point IN for control, adjacent angles are measured γ 1 and γ 2, forming a closed corner polygon. Therefore, this method is called the design polygon method . During precise alignment work, the corners of the polygon are equalized, and the coordinates of the point are calculated from them and the design distances WITH, compare them with the design ones and, if necessary, reduce them to the design position.

With a rare alignment basis, the design polygon method can be used to lay out all intersection points of the main axes of the structure from one starting point. In this case, the design path with the design angles and distances is laid completely.

Work on the breakdown of artificial structures located on the axis of the existing railway. paths and on the designed bypass have almost no differences.

In both cases, it is necessary first of all to check and restore the correct position of the track axis.

In the case where the structure is located on a direct path, proceed as follows.

At a distance of at least 200 m from the structure in one direction or the other, sections of a well-aligned track are selected and a theodolite is installed on the axis of the track of one section, and on the axis of the track of the other section - milestone.

Then the theodolite is pointed at the pole and the axis of the path is attached along a vertical thread, setting the poles “towards themselves”, i.e. bringing their installation closer gradually from the initial milestone to the theodolite.

Two of these milestones must be placed near the artificial structure on both sides so that any point on the earth’s surface within the project’s intended location for the structure can be seen from them.

The reference points for laying out the structure on the straight section of the bypass should be the turning angle points.

To break and secure the axis of the structure, which coincides with the axis of the track, in low places of its location, i.e. to project it onto the terrain, it is necessary to move the theodolite to the installation site of one of these milestones and, orienting it to a remote milestone on the axis of the path, then use the milestones to mark the position of the axis of the structure along the entire lowered part.

If the shore closest to the theodolite is not visible, then the theodolite must be rearrange the milestones, located on the opposite bank, and repeat the above breakdown.

After breaking out the longitudinal axis of the structure, the position of the transverse axis is broken down. It determines the location of the structure on the railway line.

This provision is indicated in the construction project:

if the structure is being erected on a stretch, then its position is indicated by the picketage of the line;

if it is constructed on station tracks, then most often its position is indicated relative to the station axis.

According to these data, using a steel tape, they lay down distance from the nearest picket or another firmly fixed point indicated in the project and hammer in a stake.

An ecker or theodolite is installed at this point, centered, oriented along the axis of the track and a right angle is struck on both sides of the axis of the track. The direction of the axis is indicated by milestones.

If the angle in the project is not 90°, then the ecker cannot be used and the required angle is marked with a theodolite or goniometer. This completes the breakdown of the axes of the structure.

The axles are usually secured with piles with a diameter of 10-12 cm, driven into the ground by hand to a depth of about 0.7 m or pillars dug to a depth of about 1 m. Such pillars are installed one or two at each end of the longitudinal and transverse axes.

One of these pillars can be made high-altitude benchmark. Moreover, if the construction of the bridge will last more than a year or the breakdown is done in the fall for next year’s work, then the benchmark must be buried 0.25 - 0.50 m below the freezing depth of the soil.

In addition, at the lower end of the benchmark it is necessary to cut and nail two mutually perpendicular strips to prevent the benchmark from sticking out of the ground when the upper layers of the soil freeze.

Axis

In order to more accurately secure the position of the axle on the posts securing the axle, you should first, instead of poles indicating the direction of the axes, hammer in small pegs or stick pins from the tape into the ground.

Then, at a distance of 2 m from these studs, four pegs must be driven into the ground, located at the ends of two straight lines intersecting the stud, and a wire should be pulled between them in pairs through hairpin and secure the position of the wires either with nails or notches on the stakes.

Having then removed the wires and the pin, they drive a pile instead of the latter or dig a hole to install the post.

When the pile is driven or the post is installed, the wires are pulled through the notches on the stakes again and at the point of their intersection a nail is driven into the post or a notch is made.

We can also recommend driving, flush with the ground surface, near each pillar at a distance of 1 m towards the structure (or away from it, depending on the conditions of preservation) in the direction of the axis of the structure, more sections of iron pipe with a diameter of 2-2.5 cm, a length of 0.5- 0.7 m for control in case of damage to pillars during construction work.

To protect against damage, the poles should be painted white or red and fenced. If the ground is rocky, then instead of installing pillars, the surface of the rock at the axis point is cleared and leveled, two grooves intersecting at the point are cut out with a chisel, and sometimes a circle with a diameter of 10-20 cm is cut around the point.

The grooves and circle are painted over with oil paint.

If the structure is located on a curve

If the structure is located on a curve, then first of all the curve is checked by re-staking it.

To do this, you need to measure, calculate and straighten the curve if the structure to be broken is built on an existing path.

If the structure is designed on a site located along a curve, where there is no rail track at the time of laying out, then it is necessary to lay out the curve from tangents using the ordinate method or the angle method.

To do this, first of all you need post directions of straight lines, adjacent to the curve, find the point of their intersection and measure the angle of rotation with a theodolite.

Then, using the radius of the curve and the lengths of the transition curves specified in the project, make the main and detailed breakdown of the curve after 10 m.

After this, by measuring with a tape along the axis of the curve, a point is designated WITH(Fig. 101) location of the transverse axis of the bridge in accordance with the design.

From this point, two more points are divided at strictly the same distance from it A And IN so that they are outside the scope of the work. Between points A And IN draw a straight line and find its middle WITH 1 .

If now at this point we restore the perpendicular with an ecker or theodolite, then it should pass through the previously set point WITH, and this perpendicular will be the transverse axis of the bridge.

The transverse axis is continued in both directions from the longitudinal axis of the bridge and is marked with milestones or pins at points D And E outside the scope of work.

Then all four points A, IN,D And E on the straight axis of the bridge they are secured with pillars, piles or notches on the rock.

Detailed layout of bridge supports is usually made from a straight axis AB. If local conditions require this, you can also split the auxiliary straight axis A 1 B 1 outside the scope of work and also provide a detailed breakdown regarding it.

The position of the centers of individual supports of a small bridge on a curve is established from a rectilinear axis using the coordinate method. If all spans are the same, then they stand with a theodolite in the center ABOUT each support (Fig. 102):

measure the angle between the three centers of the supports and, dividing this angle in half, obtain the direction on the axis of the support or hang the chord rs(see Fig. 102), connecting the centers of the supports adjacent to this support ABOUT, find the middle of this chord and restore a perpendicular to it with an ecker nm, giving the desired direction of the support axis.

If the supports are located at unequal distances, then the auxiliary points used to divide the direction of the support axes should be divided on the curve symmetrically relative to each support, as described above.

The layout of the main axes AB and DE (see Fig. 101) should be checked.

To do this, determine by the chainage position of the middle WITH(Fig. 103):

the broken bridge and the beginning of the curve NK distance to the bridge axis from the beginning of the curve NK.

Using the length of the curve (twice the distance) and its radius, find the corresponding tangent values from the tables T, bisectors B and rotation angle A.

After this, the found length is measured on the ground from the beginning of the curve T.

Here at the point F place a theodolite and divide the bisector of the angle, for which, using a theodolite, an angle equal to 90-(α/2) is laid off from the tangent line with the help of a theodolite. The direction of the pipe axis, with correct layout, will point to the previously divided points WITH,D and indicating the direction of the transverse axis of the bridge.

Length F.C. must be equal to the bisector B. The position of the points A And IN can be checked by breaking them down using tables using the ordinate method relative to the beginning of the curve NK.

All of the above actions assume that the breakdown is carried out in a dry valley or the width of the watercourse does not exceed 1 m.

If the river is wider, then in all places where stakes and piles are installed, simple scaffolding should first be arranged on piles or trestles.

In the second case, when it is necessary to break the axis of the place on a route traced and fixed by picketing, work also begins with restoring the longitudinal axis of the structure.

To do this, you need to find on the ground the corner posts installed during tracing at the corners of rotation.

The axis of the bridge is defined by the two vertices of the rotation angles behind the opposite ends of the bridge.

The bridge axis is hung between these two points, as described above in the first case. In the same way as described there, the transverse axis of the bridge is broken and secured.

The layout of the axes of the structure on a bypass located on a curve is no different from the case of a bridge located on a curve on the main track.

The angular notching method is used to lay out inaccessible points located at a considerable distance from the starting points. There are direct and reverse corner serifs.

In the direct angular intersection method, the location of the design point on the ground WITH(Fig. 1) are found deposited at the starting points A And IN design angles 1 and 2. The basis of the notch is either the specially measured side or the side of the alignment network. Design angles 1 and 2 is calculated as the difference between the directional angles of the sides. Directional angles are found from solving the inverse geodetic problem using the design coordinates of the point being determined and the known coordinates of the starting points.

Figure 1 - Layout scheme using straight and linear notches

Reverse corner cutting method. Approximate position is found on the ground ABOUT" point to be staked ABOUT(Fig. 2). At this point, a theodolite is installed and angles are measured with the required accuracy to at least three starting points with known coordinates. Using resection formulas calculate the coordinates of an approximately certain point and compare them with the design values. From the difference in coordinates, the reduction values (angular and linear elements) are calculated and the point is shifted to the design position.

To control the angles at this point, calculate its coordinates again and compare them with the design ones. In case of unacceptable discrepancies, all actions are repeated.

Figure 2 - Scheme of the reverse corner cutting method

Linear notching method

In the linear intersection method, the position of the point to be staked out WITH

(see Fig. 1) are determined at the intersection of design distances S 1 And S 2 , plotted from the original points A And IN. This method is usually used to lay out the axes of building structures in cases where the design distances do not exceed the length of the measuring device.

It is most convenient to carry out the breakdown using two tape measures. From point A measure the distance using a tape measure S 1 , and from the point IN on the second roulette − S 2 . Moving both roulettes with the zeros aligned with the centers of the points A And IN, at the intersection of the ends of the segments S 1 and S 2 find the position of the point to be determined WITH.

2.3 Polar coordinate method

In this method, the position of the determined point WITH(Fig. 3) are found on the ground by deposition from the direction AB design angle and distancesS. The design angle is found as the difference between the directional angles α AB and α AC, calculated as well as the distance S from solving inverse problems using the coordinates of points A, B And WITH. To control the position of a fixed point WITH can be checked by measuring at the point IN angle β" and comparing it with the value obtained as the difference between the directional angles α BA and α BC.

Figure 3 - Layout scheme using the polar coordinate method

If the point to be laid out is located at a considerable distance from the starting point, then it is necessary to postpone the design angles and distances several times using the polar method, laying out the design course (Fig. 4). If there is direct visibility from the Sleep point, the point IN for control, adjacent angles are measured And , forming a closed corner polygon, which is why this method is called using the design site method. During precise alignment work, the corners of the polygon are equalized, the coordinates of point C are calculated from them and the design distances, they are compared with the design ones and, if necessary, reduced to the design position.

With a sparse alignment, the design polygon method can be used to lay out all intersection points of the main axes of a structure from one starting point. In this case, the design path with the design angles and distances is laid completely.