This standard specifies the layout principles, survey methods and accuracy indicators for the establishment of first- and second-class leveling networks throughout the country, and is applicable to the layout of the first- and second-class leveling networks. GB/T 12897-2006 National first- and second-class leveling measurement specifications GB/T12897-2006 Standard download decompression password: www.bzxz.net
This standard specifies the layout principles, survey methods and accuracy indicators for the establishment of first- and second-class leveling networks throughout the country, and is applicable to the layout of the first- and second-class leveling networks.

ICS.07.040
National Standard of the People's Republic of China
GB/T.12897-2006
GB12897-1991
National first and second order leveling specifications
Specifications for the first and second order leveling2006-05-24 Issued
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Standardization Administration of China
2006-10-01 Implementation
Foreword·
1 Scope
Normative references
3 Terms and definitions
Leveling network:
Elevation system and elevation datum
Spot accuracy·
Layout principles:
4.4 Leveling point layout density·
Route naming and hydraulic point numbering
Connection of new routes with existing routes,
4. 7 Gravity measurement on the water route
4.8 Technical design of the leveling network
5 Point selection and stone burial
5.1 Point selection
5.1.1 Select the water jacana route
5.1.2 Select the leveling point
Describe the water push point
5.1.4 Work to be done after the point is selected
Data to be collected during point selection
Data to be submitted after point selection
5.2 Stone burial
Brown stone type
Select marble type
Water jacana marker
Burial of marker stone
5. 2. 4. 1
5.2. 4. 5
5. 2. 4. 6
Embedding of bedrock leveling stones
Establishment of rock stratum leveling stones
Embedding of concrete column leveling stones
Establishment of steel pipe leveling stones
Embedding of road leveling stones
Establishment of market foot leveling marks
External finishing of leveling stones
Control of key processes·
5.2.7 Land occupation and trusteeship of leveling stones
Stability period of leveling stones
Information to be submitted after burying the stones
Inspection and maintenance of leveling stones.
GB/T 12897--2006
GB/T12897—2006
6.1 Selection of instruments
6.2 Calibration of instruments
Only technical indicators of instruments+
7 Leveling observation·
7.1 Observation method
Observation time and meteorological conditions
7.3 Setting up observation stations
7.4 Sequence and method of observation at observation stations:
7.4.1 Observation with optical level
Observation with digital level,
7.5 Time and inspection
Observation tolerance of observation stations and setting up the plate
Observation tolerance of observation stations·
7.6.2 Starting and ending point of the round trip of the digital level section Station setup 7.7 Matters to be avoided during observation -
7. Observation of various elevation points
Observation of nodes
Detection when connecting or connecting new and old routes
Discrepancy between round trip elevation measurement and loop closure error
Re-measurement and extraction of results
8 Description of cross-river leveling observation
Scope of application
Selection of measurement method
Selection and layout of site
Requirements for cross-river leveling observation
8.5 Number of measurement rounds and tolerance
Optical micrometry
Preparation work
Observation method
Tilt spiral method
Preparation work
8. 7.2 Observation methods
8.8 Theodolite inclination method·
Preparation work:
8. 8. 2 Observation methods
8.9 Distance measurement trigonometric height method·
Preparation work
Determination of height difference between measuring stations on the local shore·
Distance measuring plate:
Vertical angle observation
8. 9. 4. 1
Observation procedures:
Observation methods·
8.9.5: Mutual difference of height difference between measuring rounds
Re-measurement and extraction of observation results
8.1 GPS leveling measuring plate method
Technical requirements
Point selection,
Label embedding:
Instruments and equipment·
Field observation·
8. 10. 5: GPS observation records, data processing and result calculation GPS baseline solution 8. 10. 7. 1 Quality check of GPS baseline solution Tenghe leveling plate GPS network adjustment processing Height difference calculation: 8.10.10 Supplementary survey and re-survey Ice survey 8.12 Night observation 9 Recording, sorting and screening of field work 9.1 Recording methods and requirements
9.1.1 Recording methods
9.1.2 Recording items
9.1.3 Recording requirements
9.1.4 Arrangement and inspection of observation records
9.2 Field calculation
9.3 Inspection, acceptance and submission of field results
Inspection, acceptance and quality assessment of results
Technical summary·
Submission of materials
Appendix A (Normative Appendix)
Format of data for selecting points and burying stones and instructions for marking stonesA.1 Tools for selecting points and burying stones
A, 2 Drawing of leveling route map
A.3 Drawing of leveling point records
A.4 Drawing of leveling network node connection cabinet
A,5 Hydraulic push mark cabinet
A.6 Hydraulic push mark stone section cabinet
A, Material placement and lubrication of sub-leveling mark stone Seven construction requirements table A,8 Contour map of extreme depth in the figure
A.9 Custody of measuring mark
Appendix (normative appendix) Instrument inspection method B. 1 Inspection of hydraulic scale
B.2 Calibration of circular level on hydraulic scale
B.3 Determination of curvature difference of hydraulic scale scale division surface
B.4 Determination of zero point inequality of a pair of leveling scales and reading difference of basic and auxiliary scales GB/T 12897-—2006
G/T12897—2006
B,5 Determination of verticality between the center axis of hydraulic scale and the bottom surface of scaleB.6 Sight of hydraulic scaleB.7 Calibration of hydraulic gauge on hydraulic scale
Determination of source moment difference and scale value of optical micrometer of hydraulic scale: B.9 Determination of error in sight observation of levelB.10
Determination of compensation error of automatic leveling level: Calibration of level ten-wire
Determination of sight band number of level
Focusing lens of level Determination of running reading error Determination of receiving error of bubble hydraulic level
Calibration of hydraulic level
Determination of dead angle of automatic leveling instrument with double pendulum Determination of error in height difference observation and vertical axis error of leveling station Determination of dynamic error and division error of hydraulic leveling device Determination of division value of leveling instrument: Determination of line error of vertical circle of theodolite Determination of error in vertical angle observation of theodolite in one measurement round Verification of error of sight distance measurement of digital hydraulic level Appendix C (Normative Appendix) Production and observation record of cross-river hydraulic leveling gauge plate c. 1
Operation of cross-river leveling sight glass
Observation records of cross-river leveling plate
Appendix 1 (Normative Appendix) Format of observation notebook and calculation of height difference tableD.1
Field observation plan of first and second grade hydraulic measurementD.2 Calculation of height difference correction number of hydraulic measurementD. 3
Field height of leveling plate and general wind scale table·
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GB/T12897—2006
This standard is a revision of GB12897—1999. This standard replaces all contents of GB12897-—1991. Compared with GB12897-1991, the main technical changes include: Modification of some technical regulations for the layout of hydraulic network a)
Modification of the specifications and technical requirements for the burial of some leveling point markers, and addition of the specifications and technical requirements for the burial of new markers
Added the technical methods and technical requirements for digital hydraulic instrument observation and inspection; added the technical methods and technical requirements for GPS cross-river hydraulic measurement: d)
Modification of some technical regulations for leveling calculation. e)
Appendix A, Appendix B, Appendix C of this standard.The appendices are all normative appendices. This standard is proposed by the National Administration of Surveying, Mapping and Geoinformation. This standard is under the jurisdiction of the National Technical Committee for Geographic Information Standardization. The main drafting units of this standard are: the Surveying and Mapping Standardization Institute of the National Administration of Surveying, Mapping and Geoinformation, the Second Geodetic Surveying Institute of the National Administration of Surveying, Mapping and Geoinformation, the Geodetic Data Processing Center of the National Administration of Surveying, Mapping and Geoinformation, and the National Basic Geographic Information Center. The main drafters of this standard are: Xiao Xuenian, Ji Henglian, Ge Zhicheng, Dong Hongwen, Li Rongchun, and Zhang De. V
1 Scope
National first- and second-class leveling specificationsbzxZ.net
This standard specifies the layout principles, survey methods and accuracy indicators for establishing first- and second-class water leveling networks throughout the country. GB/T12897--2006
This standard is applicable to the layout of national first- and second-class water leveling networks. Regional precision water leveling networks can be used as a reference. 2 Normative references
The clauses in the following standards also become clauses of this standard through reference in this standard. For all referenced documents with dates, all subsequent amendments (excluding the contents of the consultation) or revisions are not applicable to this standard. However, the parties who reach an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For all referenced documents without dates, the latest versions are applicable to this standard. GB/T3161 Optical theodolite
GB/T10156 Water pile instrument
GH/T16818 Medium and short-range photoelectric range gauge bottle GB/T 18314
Global Positioning System (GPS) measurement specification
GH50007—2002 Specification for the design of building foundations Provisions for the compilation of surveying and mapping technical summaries
CH 1001
CI1002
Provisions for inspection and acceptance of surveying and mapping products
CH1003·Surveying and mapping product quality assessment standardCH/T 1004
CH/T 2004
CB/T 2006
Surveying and Mapping Technical Design Regulations
Basic Regulations for Field Electronic Records
Zhangcha Ning Electronic Recording Regulations
JJG8 Calibration Procedure for Leveling Rod
JJG414
Calibration Procedure for Optical Theodolite
JJG425
Calibration Procedure for Leveling Instrument
JJG703
Calibration Procedure for Photoelectric Hardness Tester
JJF1ti8Global Positioning System (CPS) Receiver (Geodetic and Navigation) Control Specifications 3 Terms and Definitions
The following terms and definitions apply to this standard: 3.1
Node
A water projection point in a leveling rod that connects at least three water projection lines. 3.2
Level lag line
The level line between two adjacent nodes in the same leveling network. 3.3
Section
The leveling line between two adjacent basic leveling points in a hydraulic route. 3. 4
Leafling section
The leveling line between two adjacent leveling points
GB/T 12897—2006
Connect levelling
The observation of including a leveling point or other program point in a hydraulic route. 3. 6
Branch levelling
The observation from any leveling point in the route to any other fixed point. 3.7
Adjioning levelling
The observation of connecting any point in a newly established hydraulic route to a leveling point on another hydraulic route. 3.8
Check levelling
Observation to check whether the change of the measured quotient difference meets the requirements. 3.9
Repeated levelling
Observation repeated due to unqualified leveling. 3.10
Re-survey of leveling
Measurement of the leveling route at regular intervals. 4 Leveling network
Elevation system and leveling datum
The leveling point adopts the positive belt height system, which is calculated according to the 1985 national elevation datum. The elevation of Qingdao national origin is 72.260m. Islands should also adopt this system and datum: when there are difficulties, a local leveling origin can be established, and its elevation datum can be determined based on the average sea level obtained from the tidal data on the island. For any leveling point elevation determined by using the bureau's leveling origin, this should be noted in the leveling point result table and the relevant information of the local elevation base should be explained.
4.2 Measuring grain density
The accidental mean error M of the water level per kilometer is estimated. The mean error M of the leveling type per kilometer should not exceed the digit specified in Table 1. The average section M and the method of calculating Mw are as specified in 9.2.3 and 9.2.4. 4.3 Layout principles The unit is meter 4.3.1 The first-class leveling route should be laid along the road as far as possible. The leveling route should be closed into a ring and form a network. The circumference of the first-class leveling loop should not exceed 1600km in the eastern region and 2000km in the western region. It can be wider in mountainous and difficult areas as appropriate. 4.3.2 The first-class water network should be re-measured every 15 years, and the starting time of each re-measurement should not exceed 5 years. 4.3.3 The second-class water network is set within the first-class water ring. The second-class leveling route shall be laid along highways, roads and rivers as far as possible. The circumference of the second-class hydrographic loop shall not exceed 750km in plains and hilly areas, and may be relaxed in rural areas and difficult areas. 4.3.4 The basic points of tide gauge stations near the hydrographic route shall be measured with single precision according to the first-class hydrographic estimation. The basic network points and continuous operation stations of the national satellite positioning system, the basic network points of the national power system, the standard points of the crust monitoring network, and the settlement measurement basic points of cities and industrial areas shall be included in the hydrographic route for continuous measurement. If continuous measurement is really difficult, it can be measured by support. The measurement level is the same as that of the route. Other basic points, hydrological points, meteorological stations, etc. near the hydrographic route (hereinafter collectively referred to as "other fixed points") can be included in the route for continuous measurement or support measurement according to the requirements of the user unit. 2
4.4 Leveling point layout density
GB/T12897--2006
Leveling points should be laid out at certain intervals on the leveling route. Leveling points are divided into three types: bedrock leveling points, basic leveling points, and ordinary leveling points. The spacing and layout requirements of various leveling points should be implemented in accordance with the provisions of Table 2. Table 2
Leveling point type
Leveling point
Leveling point
Leveling point
400k right
40 km or so. Economically developed areas 20 km ~30 km Desert areas about 60 km
4 km~8 km. 2 km~4 km in economically developed areas; about 10 km in desert areas
4.5 Naming of routes and numbering of leveling points
Layout requirements
It is advisable to set it at the node of the same technical leveling route. In large cities, major national projects and areas prone to geological hazards, it should be set in additional areas with deeper rocks. The requirements can be appropriately relaxed: no less than 4 in each province (municipalities directly under the central government, autonomous region)
Set it on the first and second class leveling routes and at their nodes; in central cities; in counties and towns, it is advisable to set it in hard rock strata, at a location with stable ground + conducive to observation and long-term preservation + near the business point of the leveling route in mountainous areas; for avoidances with a length of more than 300m: near the scale points on both sides of the river where it is difficult to measure
4.5.1 The leveling route is named with the abbreviation of the starting and ending place names. The order of the starting and ending place names is from west to east, from north to south. The grades of first- and second-class leveling routes shall be indicated by I and II before the line name. 4.5.2 The water level points on the route shall be numbered in the order of 1.2, 3, etc., starting from the starting leveling point of the line. 4.5.3 The bedrock leveling point shall be named after the location where it is located, with the three characters "bedrock point" added after the place name. 4.5.4 The basic leveling point shall be followed by the character "基" and the upper and lower marks shall be followed by the characters "上" or "下" respectively. If it is a road leveling point, "道" shall be added after the end number of the leveling point, such as I京津48道. 4.5.5 The leveling branch line shall be named after the name of the elevation point it measures, with "支" added after it. The leveling points on the branch line shall be numbered in the order of 1.2.3...··· from the starting leveling point to the measured elevation point. 4.5.6 When using old leveling points, the monthly leveling point names shall be used. If it is necessary to renumber, the old name of the point when the stone marker was set should be indicated in brackets after the new name.
4.6 Connection between the new route and the measured route
4.6.1 The starting point and end point of the newly established first- and second-class leveling route should be the bedrock leveling point or basic hydraulic push point of the measured higher or equal-class route. When the whole point cannot be connected with the measured route temporarily, the future connection line should be anticipated. 4.6.2 When the newly established leveling route passes through or is close to the first and second class leveling points of the surveyed route, it is within 4km and within 1km of the third and fourth class leveling points that have been measured. When measuring the new line, the measured water push points should be included in the discussion plan for continuous measurement or connection measurement. When connecting measurement, the measured water points should be tested according to the provisions of 7.10.
4.6.3 For the connection measurement of leveling points on the measured route, the measurement shall be carried out according to the lower level accuracy requirements of the new route and the measured route. 4.6.4 When the newly established leveling route coincides with the measured leveling route, the old leveling points should be used as much as possible. When there is doubt about the stability of the old leveling point or the specifications of the old leveling point marker do not meet the requirements, the stone should be re-buried. The number of the newly buried leveling marker is the original point number followed by the four-digit year number when it was buried, and the old leveling point should be connected. 4.7 Straight force measurement on leveling routes
4.7.1 Gravity should be measured at each leveling point on the first-class leveling route. Gravity should also be measured at each leveling point on the second-class leveling route L with an elevation greater than 4000m or an average elevation difference between leveling points of 150m~-250m. In the first and second-class leveling sections with an elevation difference greater than 250m, gravity should be measured at the places where the ground inclination changes.
4.7.2 In areas with elevations between 1500tn~4000m or an average quotient difference between leveling points of 50m~150m, the average distance between gravity points on the second-class leveling route should be less than 23km. 3
GB/T12897-2006
4.7.3 The gravity measurement of leveling point .1 shall be carried out in accordance with the requirements for intensified gravity measurement. 4.8 Technical design of leveling network
4.8.1 Before laying out the first and second leveling networks, the leveling survey area, geology, hydrology, meteorology and road data should be collected in reverse order. Technical design should be carried out on the basis of the existing first, second, third and fourth leveling routes. According to the geomorphic, geological and hydrogeological conditions, and taking into account the needs of various industries, the best route should be selected to form a uniform grid.
4.8.2 The layout of the first leveling network should be carried out in sections in sequence, and each area should contain three or more satellite positioning system continuous operation stations. The start and end time of each leveling loop observation should not exceed 2 years. If the interruption time of hydraulic observation in a loop exceeds 6 months, it should be interrupted and connected at the rock point or satellite positioning system continuous operation station. If the connection points where the interruption time of leveling observation in the same leveling loop exceeds 6 months are all satellite positioning system continuous operation stations, the closing time limit of the loop can be relaxed. 4.8.3 The requirements, contents and approval procedures of technical design shall be implemented in accordance with CH/T1004. 5 Site selection and rock burial
5.1 Site selection
5.1.1 The leveling route shall be selected on roads with smaller slopes and large exposed areas as much as possible; a) areas with strong pine trees and areas with very strong terrain shall be avoided; b) expressways shall be avoided; d) streets with frequent pedestrians and vehicles, large rivers, tidal bores, swamps, valleys and other obstacles shall be avoided as much as possible; when the first-class leveling route passes through a large rock fault zone or an area with unstable geological structure, it shall be jointly studied and selected with the relevant geological and geotechnical departments.
5. 1.2 Selecting the leveling point
The water leveling point should be selected at a location with a stable foundation, representative of the ground business, and conducive to long-term preservation and remote measurement, and convenient for the determination of coordinates by satellite positioning technology.
Water leveling points should be selected near government offices, schools, and parks near the route tunnel. Road leveling points set on the shoulder should be selected near the monument or fixed orientation objects on the road (within 2). The following locations are not selected as extended leveling points! Locations susceptible to flooding or with high groundwater levels: a) Landslides, slopes, subsidence, uplift and other ground deformations are prone to occur: embankments, riverbanks, swamps and places with large groundwater level changes (such as oil wells and machine wells) + 50m from the railway, 30m from the highway (except for ordinary leveling points) or other locations that are subject to violent movement: d) Buildings that are not being adjusted or are about to be renovated:
Locations where the marking stone will be removed due to construction in the short term or where it is inconvenient to observe; g) Sections on the road 1 town.
5. 1.3 Selection of bedrock leveling points
Bedrock hydraulic push points should be selected on the outcrop of the bedrock or on the bedrock not more than 3m below the ground. When selecting bedrock leveling points, geological personnel should be involved, and the existing data should be collected and analyzed. On-site surveys should be conducted to understand the geological structure, the nature of the rock and soil, the adverse geological phenomena and groundwater. If the existing data cannot meet the requirements, necessary exploration should be carried out. After the non-leveling point is selected, the geological survey report shall be submitted point by point: the content of the geological survey report includes: a) the geodetic coordinates, topography, geomorphology, geological structure, adverse geological phenomena, stratification conditions, and physical and mechanical properties of rocks and soil of the leveling point; b) the stability of the ground, the uniformity of cracks and rocks, and the allowable bearing capacity, the depth and variability of groundwater, the maximum freezing depth and melting depth of ten, and the engineering geological hazards that may occur after the leveling point is set. Improvement suggestions: the upper geological map within 50m around the point and the geological characteristics map of the leveling point pit. The preparation of the geological survey report shall refer to the provisions of Article 3.C.3 of GB500072002. 4
5.1.4 What should be done after the point is selected
GB/T12897-2006
After each leveling point is selected, a point mark with a point number and a marker type should be set. According to the requirements of A.3 and the format of Figure A.2, the water level point record should be filled in. In the process of selecting the leveling route, the leveling route map should be drawn section by section according to the requirements of A.2. See Figure A.1 for a sample. The nodes of the leveling network should be filled in the node connection map according to the requirements of A.4 and the format of Figure A.3. 5.1.5 Supplementary information to be collected during point selection
If the required information is not fully collected during the technical design, the natural geography, transportation, material supply, sand and water sources, human resources and other relevant information on the area and landscape should be collected during the point selection. 5.1.6 Data to be submitted after the site selection is completed:
) Records of leveling points, leveling route map, route node connection map; h) Geological survey report of bedrock leveling points; other relevant data collected during site selection;
Technical summary of site selection work (mainly explaining the natural geographical conditions of the survey area: implementation of site selection work and suggestions for burial and observation work; utilization of old leveling markers: types of proposed leveling markers, statistical tables of numbers, etc.). 5.2 Buried Stones
5.2.1 Types of Benchmarks
Based on the different buried locations, materials and buried specifications, leveling point markers are divided into 1 type of markers as listed in Table 3. Among them, road leveling markers are water-permeable leveling markers buried on the shoulders of roads. Table 3
Types of Benchmarks
Yanyan Water Holding Points
Basic Benchmarks
Ordinary Benchmarks
Deep Bedrock Leveling Marks
Shallow Bedrock Leveling stone
Lao Zhanhua basic water standard stone
Concrete E column basic leveling stone
Steel pipe basic leveling stone
Standard stone history
Permafrost area pipeline basic water standard stone
Sand mold ground and concrete column mushroom basic leveling standard rock layer ordinary leveling stone
Concrete living road leveling stone
Steel pipe general wine leveling stone
Water paint area steel pipe general road water standard stone||tt| |Claim Han area concrete column general leveling stone road water goose mark stone
Slope foot water mark
The buried specifications and materials of the mark stone refer to 4, 6 and A.7.5.2.2 Selection of buried stone type
The type of water leveling point mark stone shall be specially considered according to the geological conditions. The type of mark stone of other leveling points shall be selected according to the soil exploration and soil conditions according to the following principles: a) There are rock outcrops or the depth is not more than 1.5m below the ground Location: Priority should be given to burying the level mark: b) In desert areas or areas with frozen soil depth less than 0.8m, concrete leveling stones should be installed; c) In frozen soil depth greater than 0.8m or in waterlogged areas, steel pipe leveling stones should be installed. There are solid buildings, memorials, towers, bridges, etc. and solid stone sights, and the level mark can be buried: d
e) For ordinary leveling points in water network areas or economically developed areas, road leveling marks can be buried. 5
GB/T 12897—2006
5.2.3 Leveling Marks
A gold flag leveling mark made of copper or stainless steel should be embedded in the center of the top surface of the leveling stone. Road-avoiding leveling marks are made of yellow-brown PVC material. Leveling points included in the national spatial data infrastructure should use the common mark of coordinates, business and gravity measuring plates. Marking specifications are shown in A.5.
5.2.4 Burying of benchmark stones
5.2.4.1 Burying of bedrock level benchmark stones
5.2.4.1.1 The burial of deep bedrock (the depth of the rock layer from the ground is more than 3m) leveling stones should be designed according to geological conditions, and single-layer or multi-layer protective and enhanced leveling stones should be designed and constructed by professional units. 5.2.4.1.2 Burial of shallow bedrock (the depth of the rock layer from the ground is not more than 3m) leveling stones 5.2.4.1.2.1 Prefabricated steel skeleton
The skeleton of the concrete column is made of 3 foot bars with a diameter of 10mm and 6mm diameter steel bars, and a circle of variable bars is tied every 0.3m to form a three-axis column. The foot bars are bent into a half-line with a diameter of 25mml. The steel bars are formed into an equilateral triangle with a length of 175mm, and the variable bars are stacked and tied tightly. The length of the tied steel skeleton is equal to the length of the concrete column plus 0.1㎡. The steel frame of the concrete base is cross-bound into a mesh with 10mm diameter steel bars, and the two ends of the steel screen are bent into half-widths with a true diameter of 25mm. The specifications and shapes of the frame are shown in the relevant cross-section diagram of the benchmark stone in A.6. 5.2.4.1.2.2 Excavation of the benchmark stone pit
The benchmark stone pit is excavated with the selected point mark as the center, and the size is convenient for operation. The benchmark stone pit is excavated to the vertical rock surface. 5.2.4.1.2.3 Construction of the base
On the hard rock surface after removing the weathering layer, the base pit is excavated according to the size of the rock layer level benchmark stone base. Holes with a diameter of 20mm and a depth of 0.1\ are drilled at the four corners and the center of the base pit. The holes at the four corners are required to be about 0.1m away from the edge of the base pit and symmetrical with the holes in the center of the base pit. A steel bar with a diameter of 20mm and a length of 0.25m is driven into each hole. Before building the foundation, clean the foundation pit and pour concrete to the depth of the pedestal. After sufficient consolidation, install the foundation steel frame and tie it to the steel bars embedded in the rock layer. Install the column steel frame vertically in the center of the foundation wall. Tie the bottom of the column steel frame to the foundation steel frame firmly. Then pour concrete to the top surface of the foundation. After sufficient consolidation, make the concrete surface level. If the hard rock surface is not more than 0.4m from the ground, place a hydraulic mark on the foundation wall at 0.2m from the stone column on the north right side of the mark: the lower mark; if the rock layer depth exceeds 0.4m, the lower mark should be placed on the north side of the stone column, 0.2m below the column surface. 5.2.4.1.2.4 Construction of the marker column
a) Construction of the marker column using the model plate
After the concrete of the base solidifies (about 126 at room temperature), vertically install the column model plate layer by layer in the center of the base (make the lower mark hole face north when the model plate is installed). After pouring the concrete room\the lower mark hole and fully tamping it, place the mark in the lower mark hole, and then pour concrete to the surface of the column model plate. Press the short level mark in the center of the column top. The mark should be placed straight and level. The top surface of the concrete should be smoothed. After the concrete solidifies (about 12h at room temperature), remove the formwork, add the mark iron protective cover and cement protective cover (apply oil to the inside of the iron protective cover) before backfilling, and do the external finishing. The buried specifications and conditions are shown in Figure A, 9. b) Use prefabricated culverts to build the marker stone column.
Use a standard filter concrete pipe with an inner diameter of 0.25m to replace the model plate to make the marker stone column. The total length is the specified column height plus half of the base length.
When the concrete base is half poured, put the base steel frame, insert the column steel frame into the cleaned culvert (the foot-shaped elbow at the lower end of the foot bar should protrude about 0.2m from the culvert wall), use a lifting device to hang the culvert and the column steel frame above the center of the base, tie the bottom of the column steel frame and the base steel frame to the center of the base, and drop the pipe on the center of the base and the culvert. Use objects to support the culvert in a plumb state, and pour concrete up to the top of the base. After the initial setting of the concrete of the base (about 1h at room temperature), a layer of covering material is placed on the base, and soil is filled into the marking pit and compacted to about 0.3m below the ground. When backfilling, the culvert should be kept in a plumb state. A hole with a diameter slightly larger than 30mm is drilled on the north side of the culvert 0.2m away from the upper end of the culvert for placing the marker. Concrete is poured in the culvert to the lower marking hole, and the marker is placed. The concrete is poured out to the top of the culvert, and the lower gas is discharged by vibrating. A water plate is installed on the top of the culvert.
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