The construction of municipal engineering is mainly divided into two aspects: road engineering and drainage engineering. The measurement of municipal engineering is often complicated and variability in urban construction because of the surrounding construction environment and geographical location. This requires us to determine the construction plan according to the construction drawings and the surrounding buildings and surrounding underground pipelines. Based on years of construction experience, the municipal engineering construction survey is divided into two parts: road construction measurement and drainage construction measurement.
1 Road construction survey
1.1 Construction side pile determination
After the start of the road project, the piles of the design institute in the center line will be destroyed due to road excavation. Therefore, two rows of construction side piles are often nailed on both sides of the road line outside the road line (for example, existing structures on both sides of the road can also be marked on the structure), wherein the side piles are marked with the distance to the road, and Mark the station number and elevation (high-level use and design road elevation elevation mark).
1.2 Longitudinal and cross-section measurements
Longitudinal and cross-section measurements can be made by mid-line measurements, side-by-side pile lines, and control coordinates and leveling points (currently using software as a road earthwork calculation expert). The main purpose of the longitudinal section and cross section measurement is to calculate the earthwork volume. Therefore, after the measurement of the longitudinal section and the cross section is completed, the measurement results should be checked against the engineering quantity on the design drawing. If the deviation is small after comparison with the design drawings, the original engineering quantity shall prevail. When there is a large difference between the engineering drawings and the design drawings, the supervision engineer shall be notified immediately to make the verification and change. The earthwork review work must be carried out before the construction of the road works. If the actual measured earthwork volume at the site does not match the designed earthwork volume, the report shall be submitted to the supervisor before the construction. Some projects only submitted to the supervisor after the excavation of the pipeline foundation, and the actual measured earthwork volume did not match the designed earthwork volume. Re-testing and increasing the visa were required. The general supervision was rejected. Therefore, we must pay attention to the timeliness of the work. It should be noted that in addition to satisfying the number of points specified in the specification, it is appropriate to add some points, such as hillsides or potholes, where the amount of earthwork increases or decreases.
1.3 Subgrade engineering release line
During the construction, the elevation and standard cross-section drawings are first designed according to the design profile view, and the subgrade center elevation and side pile setting are carried out on the ground (this step has been completed when the first step is applied to the pile), and the contractor pulls the wire during construction. When the contractor pulls the wire for construction, the surveying personnel must re-test the accuracy of the contractor's release point at any time to avoid reversing the wire pull-down error. It should be noted that the total station position or the original well position of the road must be marked and recorded before using the total station or GPS before excavating the roadbed.
1.4 cement stabilized macadam base layer release line
Water stable bottom layer construction can still be used to measure the height of the piles on both sides of the road. The same measurement personnel should conduct random inspection at any time to avoid errors. The construction of the side-level stone foundation should be carried out after the completion of the water-stable foundation. The foundation thickness is constructed according to the standard, which requires that the roadside line elevation must be controlled according to the design and construction when the subbase water is stable.
1.5 side flat stone masonry laying line
Due to the increased accuracy requirements of the leveling stone, this step requires the use of a total station or theodolite for edge measurement.
1) Straight line segment. Due to the error of the measuring instrument, the measuring data and the placement operation, the points on the same line on the map are generally not exactly on the same line after being placed on the ground. Therefore, it is necessary to straddle and straighten as many straight lines as possible through or near the temporary point. The threading can be carried out with a total station or theodolite. Finally, two or more control piles are laid at points A and B or their direction lines, and the straight line is fixed on the ground. When using the total station or the theodolite to thread, the instrument can be placed at point A, and then the point B is taken. After the direction is determined, the threading and placing work can be performed. When there is no special requirement for the straight line stakeout, a pile is set at 20m, and the side of the stone top is elevated. Put it on the pile at the same time.
2) Curve segment: After calculating the coordinates of each station on the curve, use the total station to set a point according to 10m. Similarly, the side stone top elevation is placed on the pile.
1.6 Water stable base layer construction stakeout
Since the construction of the road side stone has been completed, the road alignment has been basically determined, so the water stability base layer no longer needs to do line control, only need to do elevation control. The construction of water-stable base has begun to be paved with pavers, so the elevation control is controlled by the line method. Traction method construction: The main form of the line method is steel wire rope method and aluminum alloy rail method (currently, our company uses aluminum alloy rod to control elevation), the two methods are basically the same. The road elevation can be applied to the fixed steel or aluminum alloy rail bracket according to the road mileage and the cross slope position of the line. During the construction process, the surveying personnel still need to conduct random inspections on the road elevation to avoid errors.
1.7 asphalt surface layer construction stakeout
Before the asphalt construction, the paving machine should be determined in advance, the edge line should be sprinkled according to the width, and the cement stabilized gravel cross section should be measured, and the road surface elevation should be compared. The pavement and the road height can be paved by reasonable adjustment. .
2 drainage engineering construction measurement
Properly performing the lofting work of drainage works such as pipes and trenches according to the design drawings is an important work content of drainage engineering measurement. Whether the construction stakeout is accurate or not has a direct impact on the progress and quality of the project. Therefore, the surveyor should carefully read the drawings, carefully review the elevation of each part, and understand the design intent so that the measurement work can be done in a timely and accurate manner. In addition to the general preparation work, the construction survey of the drainage project shall also test the plane position and elevation of other above-ground and underground structures where the existing pipe and ditch entrance and exit intersect with the pipeline. If the data is found to be inconsistent with the design data or other The problem should be solved in time with the design unit.
2.1 Determine the pipeline centerline
The various pipeline works for new construction projects should be determined according to the road design standard cross-section and plan. The surveyor should first understand the relationship between the pipeline centerline and the road centerline, and then set up the pipeline centerline based on the road centerline. When measuring the pipeline centerline, the center pile shall be set at the starting point, the end point, the plane vertices and the control points of the straight line section and the inspection well according to the design drawing, and shall be set at appropriate positions outside the trench excavation range at these points. Construction control piles.
2.2 Find out the actual situation on site
1) After the design of the yard to control the level of the pile, use the level gauge to measure the upstream and downstream access points of the pipeline to see if it is consistent with the design access point elevation. If the inconsistency is made, report the materials to the owner and the design institute. Request to get an official document).
2) After releasing the open line of the pipeline before excavation, excavate the pit along the line of the pipeline organized by the owner, and excavate the pit along the line (belonging to the visa scope, the supervision confirms the amount of the project), and expose the original underground pipeline within the road range. Properties such as well location, material, depth, direction, and type are marked on the drawing by position and a table is drawn.
2.3 Determine the slotted edge
After releasing the pipeline centerline, determine the width of the upper opening of the trench according to the excavation depth, and release the edge line for excavation on both sides. If the working surface is not allowed to open the width of the opening, determine the other construction methods according to the actual situation and the owner, supervision and design, and complete the special scheme. Construction is possible.
2.4Comparing drawings according to actual measurement results on site
According to the pile number, the excavation position of the pipeline is measured in situ, and the actual excavation depth is consistent with the excavation depth of the design drawing. If the discrepancies are serious, the problem may be the level error, the field measurement error, the drawing error, the actual site. There is a deviation between the situation and the design. If this happens, it should be checked item by item immediately to avoid big mistakes.
2.5 Measurement considerations during construction
1) During the pipeline excavation process, the surveyor requires the surveyor to use the level gauge to track the measurement. It is strictly forbidden to lay the pile in advance and hand over to other personnel to control the elevation.
2) Beginning of trench excavation, firstly determine the approximate excavation depth according to the previous measurement results. Stop digging when the excavation is close to the design elevation of the pipeline structure bottom 30cm. According to the inner bottom elevation (over the water surface), turn up 1m (upwardly For any height, as determined by the actual situation, the piles shall be flattened on both sides of the groove. At the same time, in order not to affect the degree of compaction at the bottom of the groove, the machine shall not be directly digging to the bottom of the pipe structure. 20cm should be reserved according to the height of the flat pile. The wall thickness + pipe structure is manually excavated and flattened at the bottom of the groove. During the trench excavation process, the direction of the trench is checked and measured at any time by using the roadside pile to avoid the trench digging.
3) After the pipe groove is completed, use the instrument at the bottom of the groove to re-release the center line at the bottom of the groove and release the elevation according to the pile number on the center line, and add the elevation pile at the well position to control the bottom hole elevation.
2.6 Construction points of caisson measurement
Sinking sinking control:
1) During the sinking process of the wellbore, it is easy to tilt and should be noted. In the case of poor soil quality and rapid sinking to the design elevation, there is still the possibility of tilting the wellbore. Therefore, you need to pay attention to the measurement at any time and correct it in time.
2) There are many reasons for the inclination during the sinking of the wellbore, mainly because the soil under the foot of the lower part of the wellbore is uneven, the earth pressure around the well wall is unbalanced, the operation mode of the excavation is asymmetrical, and there is an obstacle at some point under the blade. caused.
3) Observing the inclination of the wellbore generally uses the top measurement method, using the level gauge to measure the elevation along several fixed points on the wellbore, calculating the inclination of the wellbore through the elevation difference, and then taking effective measures to correct the deviation.
4) When the sinking sink is close to the design elevation, the observation frequency should be increased. In order to prevent the self-sinking from being too fast, the blade foot soil should not be dug. Once it sinks to the design elevation, the bottom is sealed immediately.