JGJ/T 8-1997 Specification for building deformation measurement JGJ/T8-97
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Engineering Construction Standards Full-text Information System
Industry Standards of the People's Republic of China
Specifications for Building
Deformation Measurements
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Industry Standards of the People's Republic of China
Specifications for Building Deformation Measurements
MeasurementsJGJ/T8—97
Editing Unit: Comprehensive Survey, Research and Design Institute of the Ministry of ConstructionApproving Department: Ministry of Construction of the People's Republic of ChinaEffective Date: June 1, 1998
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Notice on the Release of the Industry Standard
"Code for Measurement of Building Deformation"
Jianbiao [1997] No. 308
In accordance with the requirements of the former Ministry of Urban and Rural Construction and Environmental Protection's Chengke (84) No. 153 document, the "Code for Measurement of Building Deformation" edited by the Comprehensive Survey, Research and Design Institute of the Ministry of Construction has been reviewed and approved as a recommended industry standard, numbered JGJ/T8—97, and will be implemented on June 1, 1998.
This code is managed by the Ministry of Construction's Survey and Geotechnical Engineering Standards and Technology Management Unit, the Ministry of Construction's Comprehensive Survey, Research and Design Institute, and the specific interpretation and other work is the responsibility of the editor-in-chief. It is published by the Ministry of Construction's Standards and Norms Research Institute. Ministry of Construction of the People's Republic of China
November 14, 1997
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General Provisions
Elevation Control
3.1 Grid Point Layout...
..2 Main Technical Requirements.
3.3 Geometric Leveling
3.4 Liquid Static Leveling
Plane Control|| tt||..·..
4.1 Network point layout
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Main technical requirements
Horizontal angle measurement
4.4 Distance measurement
5 Settlement observation
Building settlement observation
Foundation pit rebound observation
Layered settlement observation of foundation soil
Construction site settlement observation
Digital displacement observation
Building main body tilt observation
Construction Observation of horizontal displacement of buildings
Observation of cracks
Observation of deflection
Observation of deformation under sunlight
Observation of wind vibration
Observation of landslides at construction sites
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7Data processing
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General provisions
Verification of observation results
Adjustment of observation results
Deformation analysis
Collation of deformation measurement results
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Types of elevation control point markers
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Types of observation piers and gravity balance ball aiming marks -* 56
Type of settlement observation point mark
Settlement observation result map
Displacement observation result map
Terms used in this code
Additional explanation
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1 General
1.0.1. This code is formulated to achieve advanced technology, economic rationality, safety and applicability, and ensure quality in building deformation measurement.
2 This code is applicable to various settlement (including rise) measurements and displacement measurements of foundations, superstructures and sites of industrial and civil buildings (including structures). 1.0.3 The deformation allowable value based on which the measurement accuracy is determined and the inspection items, methods and maintenance requirements of the instruments used for deformation measurement shall not only comply with the requirements of this regulation, but also comply with the provisions of the relevant national standards and specifications in force. Engineering Construction Standard Full-text Information System
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2 General Provisions
2.0.1 The building deformation measurement shall accurately reflect the actual deformation degree or deformation trend of the building, structure and its site, and use this as the basic requirement for determining the operation method and the quality of the inspection results.
2.0.2 Before the measurement work begins, the measurement scheme shall be designed according to the deformation type, measurement purpose, task requirements and measurement area conditions. For major projects or projects with important scientific research value, the optimization design of the monitoring network shall also be carried out. The measurement scheme shall be selected after field selection, multi-scheme accuracy estimation and technical and economic analysis comparison. 2.0.3 The implementation of deformation measurement shall comply with the following procedures and requirements: 1 According to the requirements of measuring settlement or displacement, the measurement points shall be selected respectively, the corresponding benchmarks shall be buried, and the elevation network or plane network shall be established, or a three-dimensional network may be established. The original elevation system of the survey area shall be used for elevation measurement, and an independent coordinate system may be used for plane measurement. 2 The monitoring network shall be observed according to the determined observation cycle and total number of times. Newly built large and important buildings shall be systematically observed from the beginning of their construction until the deformation reaches the specified stability level.
3 The observation results of each cycle shall be processed in a timely manner, and a reference system close to or consistent with the actual deformation situation shall be selected for adjustment calculation and accuracy assessment. For important monitoring results, deformation analysis shall be carried out, and the deformation trend shall be predicted. 2.04 Deformation measurement points can be divided into control points and observation points (deformation points). Control points include benchmark points, working base points, and working points such as contact points, check points, and orientation points. The selection and use of various measuring points shall meet the following requirements: 1 The reference point shall be selected at a stable position outside the deformation influence range for long-term preservation. When in use, a stability check or inspection shall be carried out, and a stable or relatively stable point shall be used as a reference point for measuring deformation.
2 The working reference point shall be selected at a stable or relatively stable position close to the observation target and convenient for joint measurement of the observation point. When the working reference point for measuring the overall deformation is observed according to the two-level network, the reference point or check point shall be used to check its stability before use. The working reference point for measuring the deformation of the section can be directly used as the starting point. 3 When the reference point and the working reference point need to be connected, a contact point shall be arranged. When selecting its point position, the configuration of the connection shall be taken into account, and the position shall be relatively stable. 4 For working base points or benchmarks that need to be checked for stability separately, check points should be arranged, and their positions should be selected in groups at stable positions according to the check method used. 5 For working base points or benchmarks that need to be oriented, orientation points should be arranged, and stable points that meet the aiming requirements should be selected as orientation points. 6 Observation points should be selected at positions on the deformed body that can reflect the deformation characteristics. They can be observed from the working base points or nearby benchmarks and other working points. Note: 1 Overall deformation refers to the deformation of the observation targets that are all moving points, including the absolute deformation and relative deformation of the foundation and base;
2 Segment deformation refers to the deformation of the observation target with a relative fixed point, including independent local foundation deformation, overall building deformation and structural segment deformation. 2.0.5 The classification of building deformation measurement and its accuracy requirements shall comply with Table 2.0.5.
Grades and accuracy requirements of building deformation measurement Deformation measurement grades
Note: 1
Settlement observation
Observation point and station
Mean error of height difference
Displacement observation
Observation point, etc.
Mean error of standard
Special precision engineering and important scientific research project deformation observation with extremely high accuracy requirements
Large buildings and scientific research project deformation observation with high accuracy requirements
Buildings and scientific research project deformation observation with medium accuracy requirements; heavy The mean error of the height difference of the observation point of the building main body inclination observation and site landslide observation refers to the mean error of the height difference of the observation point in geometric leveling measurement or the mean error of the relative height difference of adjacent observation points in static leveling measurement,
2 the mean error of the coordinates of the observation point refers to the mean error of the coordinates of the observation point relative to the station (such as the working base point, etc.), the mean error of the coordinate difference, and the equivalent mean error of the deviation value of the observation point relative to the baseline, and the mean error of the horizontal displacement component of the building (or component) relative to the bottom fixed point. 2.0.6 For an actual project, the accuracy level of deformation measurement should first be estimated according to the allowable deformation values of various types of construction (structures) in accordance with the provisions of Chapters 3 and 4 of this Code, and then determined according to the following principles:
1 When only a single allowable deformation value is given, the corresponding accuracy level should be selected according to the estimated observation point accuracy:
2 When multiple allowable deformation values of the same type are given, the observation point accuracy should be estimated separately, and the corresponding accuracy level should be selected according to the highest accuracy among them;
3 When the estimated observation point accuracy is lower than the third-level accuracy requirement in Table 2.0.5 of this Code, the third-level accuracy should be adopted;
4 For observation items where the allowable deformation value is not specified or is difficult to specify, the appropriate accuracy level can be selected according to the principles of design and construction, with reference to the experience of similar or similar projects, and in comparison with the provisions of Table 2.0.5. 2.0.7 The observation cycle of deformation measurement shall meet the following requirements: 1 For a single-layer network, observation points and control points shall be observed according to the deformation observation cycle. For a two-layer network, observation points and control points of joint measurement shall be observed according to the deformation observation cycle, and the control network part may be observed according to the re-measurement cycle. 2 The deformation observation cycle shall be determined based on the principle of being able to systematically reflect the change process of the measured deformation and not omitting its change moment, according to the size of the deformation per unit time and the influence of external factors. When abnormal deformation is found during observation, the number of observations shall be increased in time. 3 The re-measurement cycle of the control network shall be determined according to the measurement purpose and the stability of the point position, and it is generally advisable to re-measure once every six months. During the construction process, the observation time interval shall be appropriately shortened, and the observation time interval may be appropriately extended after the point position is stable. When the re-measurement results or test results are abnormal, or the measurement area is affected by external factors such as earthquakes, floods, and blasting, re-measurement shall be carried out in time.
4 The first (i.e., zero cycle) observation of deformation measurement shall appropriately increase the observation amount to improve the reliability of the initial value.
5 When observing at different periods, the same observation network and observation method should be adopted, and the same type of measuring instruments should be used. For special and first-level deformation observations, it is also advisable to fix the observation personnel, select the best observation period, and observe under basically the same environment and conditions. 2.0.8 In addition to using the various methods specified in this code, other methods that can meet the accuracy requirements specified in this code may also be used for building deformation measurement. Engineering Construction Standard Full-text Information System
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3 Elevation Control
3.1 Network Point Layout
3.1.1 The layout of the elevation control network shall meet the following requirements: 1 For survey areas with fewer buildings, the control points and observation points should be laid out in a single layer: For large survey areas with many and scattered buildings, the network should be laid out in two layers, that is, the control points form a control network, and the observation points and the control points measured together form an extended network. 2 The control network should be laid out as a closed loop, a node network or an elevation route. The extended network should also be laid out as a closed or elevation-adhering route. 3. Each survey area should have no fewer than three leveling base points; for small survey areas, there may be fewer than three when the point is confirmed to be stable and reliable, but there must be no fewer than three including the working base points. The benchmark stone of the leveling base point should be set in the bedrock layer or the original soil layer. In the construction area, the distance between the point and the nearby building should be greater than twice the maximum width of the building foundation, and the benchmark stone depth should be greater than the depth of the adjacent building foundation. At the point inside the building, the benchmark stone burial depth should be greater than the depth of the foundation soil compression layer. 4. The location of the working base point and the contact point should be determined according to the needs of the network. The distance between the level point as the working base point and the adjacent building shall not be less than 1.5 to 2.0 times the depth of the building foundation. The working base point and the contact point can also be set on the stable permanent building wall or foundation.
5 All kinds of leveling points should avoid traffic arteries, underground pipelines, warehouses, water sources, river banks, soft fill, landslide areas, machine vibration areas and other places where the markers and signs are prone to corrosion and damage.
3.1.2 The selection and burial of the markers of the elevation control points shall meet the following requirements: 1 The markers of the leveling base points can be selected according to the different geological conditions of the location of the point, such as rock stratum leveling base point markers, deep-textured bimetallic pipe leveling base point markers, deep-textured steel pipe leveling base point markers or concrete basic leveling base points. Engineering Construction Standard Full Text Information System
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2 The markers of the working base points can be selected according to the different requirements of the point, such as shallow-buried steel pipe leveling base points, ordinary concrete leveling base points or leveling marks on the foot of the wall or on the wall. 3 The type of the markers of the elevation control points can be implemented according to Appendix A of this specification. The specifications and burial of the stone markers in special areas and with special requirements shall be designed separately. After the stone markers and signs are buried, they shall be stable before observation can begin. The stabilization period shall be determined according to the observation requirements and geological conditions, and should not be less than 15 days.
3.1.3 For the leveling points and observation points determined by the liquid static leveling method, the setting of their points shall meet the following requirements: 1 The leveling points and observation points shall be set on the same elevation plane, and the maximum height difference between the points shall not exceed ±1cm. When some points cannot meet this requirement due to the limitations of site conditions, constant difference points with different upper and lower elevations but vertically corresponding upper and lower positions shall be set to transfer the elevation. 2 The type and burial of the observation mark shall be determined according to the model, structure, reading method and site conditions of the liquid static level used. The specification and size design of the mark shall meet the requirements for the placement of placed, suspended or fixed instruments. 3.2 Main technical requirements
3.2.1 The mean error of observation of final settlement shall be determined according to the following provisions: 1 The mean error of observation of absolute settlement (such as settlement, average settlement, etc.) can be determined according to the foundation conditions, combined with experience and analysis for projects with extremely high precision requirements; for projects with other precision requirements, ±0.5mm, ±1.0mm, and ±2.5mm can be selected according to the categories of low, medium, and high compressible foundations. 2 The mean error of observation of relative settlement (such as settlement difference, foundation tilt, local tilt, etc.), local foundation settlement (such as foundation pit rebound, foundation soil stratification settlement, etc.) and expansion soil foundation deformation shall not exceed 1/20 of the allowable value of deformation. 3 The mean error of observation of overall deformation of buildings (such as overall vertical deflection of engineering facilities, etc.) shall not exceed 1/10 of the allowable vertical deviation. 4 The mean error of observation of structural segment deformation (such as deflection of horizontal components, etc.) shall not exceed 1/6 of the allowable value of deformation.
5 For the mean error of observation of deformation in scientific research projects, the mean errors of the above observations can be multiplied by 1/5 to 1/2 coefficients and then adopted, depending on the degree of improvement in observation accuracy required. Engineering Construction Standard Full-text Information System
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3.2.2 The accuracy level of elevation measurement shall be estimated according to the unit weight mean error μ based on the mean error of final settlement observation determined in Article 3.2.1 of this Code, according to (3.2.2-1 or (3.2.2-2) formula, and after the mean error of the height difference of the observation point and station is calculated, the following shall be selected according to the provisions of Article 2.0.6 of this Code:
μ=m//20m
u=mss//2Q
where m is the mean error of observation of settlement s (mm); m△s—— Observation error of settlement difference △ (mm); Q——weighted inverse of the elevation H of the weakest observation point in the network; Q——weighted inverse of the elevation difference h between the observation points to be determined in the network. (3.2.2-1)
(3.2.2-2)
3.2.3 Geometric leveling method should be used for elevation control measurement. When geometric leveling is inconvenient or automatic observation is required, liquid static leveling method can be used. When the elevation difference between the measurement points is large and the accuracy requirement is low, short-line trigonometric elevation measurement method can also be used.
3.3 Geometric leveling
3.3.1 The technical requirements for geometric leveling observations of various levels shall meet the following requirements: 1 For special and first-level settlement observations, DSZ05 or DS05 level instruments and Invar alloy rulers shall be used to observe by optical micrometry; for second-level settlement observations, DS1 or DS05 level instruments and Invar alloy rulers shall be used to observe by optical micrometry; for third-level settlement observations, DS3 instruments and zone-type wooden rulers may be used to observe by the middle-wire reading method; DS1, DS05 instruments and Invar alloy rulers may also be used to observe by optical micrometry. The order and method of observation at each measuring station for the optical micrometry method and the middle-wire reading method shall be implemented in accordance with the relevant provisions of the current national leveling specifications. 2 In each level of observation, the number of observation lines per cycle can be estimated and determined after adjustment according to the selected level of accuracy and the type of instrument used: r = (ma/mo)2
mo—mean error of height difference of the selected level of station (mm); where
mo——mean error of height difference of each station in single-pass observation of different types of leveling instruments Engineering Construction Standard Full-text Information System
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