JGJ 6-1999 Technical specification for box and raft foundations of high-rise buildings
Some standard content:
Engineering Construction Standard Full-text Information System
Industry Standard of the People's Republic of China
Technical Code for Tall Building Box FoundationsandRaftFoundations
JGJ6—99
1999Beijing
Engineering Construction Standard Full-text Information System
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Industry Standard of the People's Republic of China
Technical Code for Tall Building Box Foundationsand RaftFoundations Foundations
JGJ6—99
Editing unit: China Academy of Building ResearchApproving department: Ministry of Construction of the People's Republic of ChinaEffective date: November 1, 1999
1999 Beijing
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1 General principles
Original language and symbols
241
42 Symbols
Foundation investigation.
General provisions
3.2 Key points of investigation
3.3 Indoor test and on-site in-situ test||t t||Groundwater
Ground water planning
Structural design and construction requirements
-General provisions
Box foundation
Ground foundation
Pile box and pile foundation
General provisions
c60660666000000090600600000006066006000000000000000000900606606600 Monitoring of affected areas
Precipitation and drainage
Excavation of foundation pit
Construction of supporting structure
Construction of box foundation and pile foundation
Construction monitoring.
Appendix A
Additional stress coefficient α, average additional stress coefficient αAppendix B according to E. Coefficients for calculating flow drop
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Appendix C Base reaction coefficient
Appendix D Calculation of critical section perimeter and polar moment of inertia of punching shear. Appendix E Explanation of terms used in this specification·
Additional explanation
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1.0.1 In order to achieve advanced technology, economic rationality, safety and applicability, and ensure quality in the investigation, design and construction of box-shaped and scalloped foundations of high-rise buildings, this specification is formulated. 1.0.2 This specification is applicable to the investigation, design and construction of box-shaped and scalloped foundations of high-rise buildings
1.0.3 The design and construction of box-shaped and scalloped foundations shall comprehensively consider the geological conditions, construction methods, use requirements and mutual influence with adjacent buildings of the entire construction site, and shall consider the joint effect of the foundation and the superstructure. 1.0.4 The survey, design and construction of the box-shaped and scalloped foundations of high-rise buildings shall comply with the provisions of the relevant current national standards in addition to complying with this code. Engineering Construction Standard Full-text Information System
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2 Terms and Symbols
2.1 Terms
Box FoundationBoxFoundation
A single-layer or multi-layer reinforced concrete foundation with good overall rigidity consisting of a bottom plate, a top plate, side walls and a certain number of internal partition walls. 2.i.2 Raft Foundation
A continuous flat plate or beam-slab reinforced concrete foundation under a column or wall. 2.2 Symbols
2.2.1 Resistance and material properties
Compression modulus of soil;
-rebound and recompression modulus of soil;
deformation modulus of soil,
f——design value of foundation bearing capacity;
-design value of axial compressive strength of concrete;-design value of axial tensile strength of concrete;-standard value of foundation bearing capacity,
adjusted design value of seismic bearing capacity of foundation soil; section moment of inertia;
resistance moment of foundation bottom surface;
-water content of soil.
2.2.2 Actions and effects
F——Design value of vertical force on top of foundation,wwW.bzxz.Net
Design value of average pressure at bottom of foundation
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-Standard value of average additional pressure at bottom of foundation;-Standard value of self-weight pressure of foundation soil at bottom of foundation;Pe
-Design value of average net reaction of foundation after deducting self-weight of bottom plate;Standard value of average pressure at bottom of foundation under combination of long-term effects;Design value of uniformly distributed load acting on lintel above opening;Standard value of load acting under opening Design value of uniformly distributed load on the lintel; Settlement;
Horizontal shear force, design value of shear force on the lintel; Design value of shear force transmitted from the bottom of the upper structure through the box foundation or the top plate of the underground structure;
When the earthquake effect is combined, the design value of shear force transmitted from the bottom of the upper structure through the box foundation or the top plate of the underground structure;
-Design value of total shear force borne by the plate at the edge of the support generated by the net reaction of the foundation after deducting the deadweight of the bottom plate;
Design value of vertical shear force transmitted to each wall by the axial force of the column root; Calculation depth of foundation settlement,
Additional stress coefficient:
Calculation value of overall inclination;
-shear stress.
2.2.3 Geometric parameters
Foundation bottom surface area
Foundation bottom surface width;
The width of the box foundation or the top plate of the underground structure consistent with the shear direction Foundation burial depth;
d. — controlled exploration point depth,
dg——general exploration point depth;
h. —effective height of the board;
building height, refers to the height from the outdoor ground to the eaves Engineering Construction Standard Full Text Information System
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——house length or unit length separated by settlement joints, In1——short side length of rectangular two-way board; In2—long side length of rectangular two-way board;
——wall thickness;
thickness of the top plate of the box foundation or the underground structure; eccentricity,
perimeter of the critical section of punching shear.
Calculation coefficient
Shear stress coefficient of the unbalanced bending moment between the slab and the column transmitted to the periphery of the critical shear section;
Bending stress coefficient of the unbalanced bending moment between the slab and the column transmitted to the periphery of the critical shear section;
Deep adjustment coefficient for settlement calculation;
Adjustment coefficient for the required bearing capacity of foundation soil:
Shear force distribution coefficient;
Correction coefficient for foundation settlement calculation;
Empirical coefficient for settlement calculation;
Empirical coefficient for settlement calculation considering the influence of rebound. Engineering Construction Standard Full Text Information System
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3 Foundation Investigation
3.1 General Provisions
The following main tasks shall be carried out in foundation investigation: (1) To determine whether there are any adverse geological phenomena that may affect the stability of the project, as well as the existence of ancient river channels and artificial underground facilities in the construction site and its adjacent areas; (2)
Nature;
To determine the stratigraphic structure and uniformity of the construction site and the engineering properties of each rock and soil layer; To determine the type of groundwater, burial conditions, seasonal variation range and corrosiveness to building materials;
In the earthquake-resistant fortification zone, the areas that are favorable, unfavorable and dangerous for the earthquake resistance of the building shall be divided;
The soil type of the site and the category of the construction site shall be determined; and to determine whether there are liquefiable soil layers in the site.
The survey report should include the following main contents: basic geological conditions and analysis of the construction site; recommended solutions for foundation design and foundation treatment; calculation parameters required for the bearing capacity and deformation calculation of natural foundation or pile foundation; site hydrogeological conditions, groundwater storage conditions and change range. When the foundation burial depth is lower than the groundwater level, suggestions should be made on the construction dewatering plan and the impact on adjacent buildings and relevant technical parameters should be provided; (5D analysis of the stability of the slope of the foundation pit opening control, and support plan should be proposed if necessary 3.2 Exploration points
3.2.1 The layout of exploration points should take into account the size of the building, load distribution and complexity of the strata, and should meet the requirements for evaluating the uniformity of the strata in both the vertical and horizontal directions of the building. The following provisions should also be met:
3.2.1.1 The spacing between exploration points should be 15~35m; when the strata changes are particularly complex, the spacing should be appropriately increased. ;
3.2.1.2 The number of exploration points for a single high-rise building should not be less than 5, of which the number of control exploration points should not be less than 2;
3.2.1.3 The exploration points should be arranged along the perimeter of the building, and should be arranged at the corners and center points. The number of exploration points should be appropriately increased at locations with large changes in the number of floors or loads. 3.2.1.4 When large-diameter piles with large bearing capacity are used under box-shaped or Xiao-shaped foundations and the geological conditions are relatively complex, an exploration point should be arranged at each pile position. 3.2.2 The depth of the exploration point should comply with the following provisions: 3.2.2.1 The depth of the control exploration point should be greater than the depth of the foundation compression layer, and can be estimated according to the following formula:
d. =d+ab
Depth of controlled exploration point;
Deepth of foundation buried;
Width of foundation bottom surface;
(3.2.2-1)
Empirical coefficient related to soil layer, take value according to Table 3.2.2 based on soil type of foundation bearing layer.
The depth of general exploration point should be based on the principle of controlling the change of main stress-bearing layer, and can be estimated by the following formula:
dg=d+agb
Empirical coefficient
Depth of general exploration point;
(3.2.2-2)
Empirical coefficient related to soil layer, take value according to Table 3.2.2 based on main stress-bearing soil layer of foundation.
Empirical coefficient &, value
Sand, gravel soil
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Clay, silt
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Note: 1. The value should take into account the soil density, groundwater level and other conditions. When it is dense soil and the groundwater level is buried deep, take a small value, otherwise take a large value.
2. In soft soil areas, the foundation width should be considered when taking the value. When 6>60m, take a small value; when 6<20m, take a large value. 3.2.2.3 The depth of the exploration point in the earthquake-resistant zone shall still meet the requirements of the current national standard "Code for Seismic Design of Buildings" (GBJ11); 3.2.2.4 For large-diameter end-bearing piles without considering the pile group effect, the depth of the control exploration point shall reach 3 to 5 meters below the expected pile tip. When the diameter of the pile tip (including the expanded bottom end) is greater than 1.5 meters, the depth of the control exploration point shall be greater than or equal to 5 times the pile tip diameter. When encountering a soft layer, it should be deepened to penetrate the soft layer. The general exploration point should be 1 to 2 meters below the pile tip; 3.2.2.5 When the friction pile foundation needs to calculate the foundation deformation, the pile group can be regarded as an imaginary solid foundation, and the depth of the compression layer is calculated from the pile tip to determine the depth of the control drilling. When the depth of the control drilling is estimated using Formula 3.2.2-1, the foundation burial depth d should be taken according to the burial depth of the pile tip. When encountering a hard rock layer or a dense gravel soil layer within the calculation depth range, the drilling depth can be reduced as appropriate.
3.2.3 The number of main and in-situ test exploration points and the amount of soil taken should comply with the following provisions:
3.23.1 The number of soil and in-situ test exploration points should account for 1/2 to 2/3 of the total number of exploration points, and a single building should have at least two soil and in-situ test holes. 3.2.3.2 The original soil samples taken from the foundation bearing layer and the main load-bearing layer should not be less than 6 pieces per layer, or the number of in-situ tests should not be less than 6 times. 3.3 Indoor test and on-site in-situ test
The maximum pressure value applied in the indoor compression test should be greater than the sum of the self-weight pressure and the expected additional pressure. The calculation of the compression coefficient and compression modulus should be taken from the pressure section from the self-weight pressure to the sum of the electric weight pressure and the additional pressure. When it is necessary to consider the influence of the deep foundation pit opening controlled unloading and reloading on the foundation deformation, a rebound recompression test should be carried out, and the application of the pressure should simulate the actual stress state of loading and unloading. 3.3.2 The shear test should adopt triaxial compression test. When the foundation is saturated soft or the load application rate is high, the triaxial unconsolidated undrained test method should be adopted. When the load application rate is low, the triaxial consolidated undrained test method should be adopted. 3.3.3 To determine the foundation bearing capacity and deformation calculation parameters of a first-class building or a building with special requirements, a flat plate load test should be carried out. The safety level of buildings is divided according to the current national standard "Code for Design of Building Foundations" (GBJ7). 3.3.4 To determine the shear strength of soft soil foundation, a cross-plate shear test should be carried out. 3.3.5 Static penetration and case pressure tests should be conducted to determine the uniformity, bearing capacity and deformation characteristics of clay, silt and sand.
3.3.6 Standard push penetration tests should be conducted to determine the density and earthquake liquefaction possibility of silt and sand.
3.3.7 Heavy or super heavy dynamic penetration tests should be conducted to determine the uniformity and bearing capacity of crushed stone soil.
3.3.8 Wave velocity tests should be conducted to obtain the parameters required for seismic design. 3.4 Groundwater
The groundwater level of the construction site should be determined, including the measured upper stagnant water, groundwater and confined water levels, seasonal variation range and the corrosiveness of groundwater to building materials. 3.4.2
For projects that require artificial lowering of the groundwater level, the survey report should include the site's hydrogeological data and the parameters of the dewatering design, make recommendations on dewatering methods, and conduct top-down measurements of the impact of dewatering on adjacent buildings and important underground facilities. Construction Standard Full Text Information System
.bzsoso.Com2-1 When estimating the depth of the controlled borehole, the foundation burial depth d shall be taken as the buried depth of the pile tip. When encountering hard rock layers or dense gravel soil layers within the calculated depth range, the drilling depth may be reduced as appropriate.
3.2.3 The number of main and in-situ test exploration points and the amount of soil taken shall comply with the following provisions:
3.23.1 The number of soil taking and in-situ test exploration points shall account for 1/2 to 2/3 of the total number of exploration points, and a single building shall have at least two soil taking and in-situ test holes. 3.2.3.2 The original soil samples taken from the foundation bearing layer and the main load-bearing layer shall not be less than 6 pieces per layer, or the number of in-situ tests shall not be less than 6 times. 3.3 Indoor test and on-site in-situ test
The maximum pressure value applied by the indoor compression test shall be greater than the sum of the deadweight pressure and the expected additional pressure. The calculation of compression coefficient and compression modulus should be taken from the pressure section from the weight pressure to the sum of the electric weight pressure and the additional pressure. When the influence of unloading and reloading of deep foundation pit on foundation deformation needs to be considered, a rebound recompression test should be carried out, and the application of pressure should simulate the stress state of actual loading and unloading. 3.3.2 The shear test should adopt triaxial compression test. When the foundation is saturated soft or the load application rate is high, the triaxial unconsolidated undrained test method should be adopted. When the load application rate is low, the triaxial consolidated undrained test method should be adopted. 3.3.3 To determine the foundation bearing capacity and deformation calculation parameters of a first-class building or a building with special requirements, a flat plate load test should be carried out. The safety level of the building is divided according to the current national standard "Code for Design of Building Foundations" (GBJ7). 3.3.4 To determine the shear strength of the soft soil foundation, a cross-plate shear test should be carried out. 3.3.5 Static penetration and case pressure tests should be conducted to determine the uniformity, bearing capacity and deformation characteristics of clay, silt and sand.
3.3.6 Standard push penetration tests should be conducted to determine the density and earthquake liquefaction possibility of silt and sand.
3.3.7 Heavy or super heavy dynamic penetration tests should be conducted to determine the uniformity and bearing capacity of crushed stone soil.
3.3.8 Wave velocity tests should be conducted to obtain the parameters required for seismic design. 3.4 Groundwater
The groundwater level of the construction site should be determined, including the measured upper stagnant water, groundwater and confined water levels, seasonal variation range and the corrosiveness of groundwater to building materials. 3.4.2
For projects that require artificial lowering of the groundwater level, the survey report should include the site's hydrogeological data and the parameters of the dewatering design, make recommendations on dewatering methods, and conduct top-down measurements of the impact of dewatering on adjacent buildings and important underground facilities. Construction Standard Full Text Information System
.bzsoso.Com2-1 When estimating the depth of the controlled borehole, the foundation burial depth d shall be taken as the buried depth of the pile tip. When encountering hard rock layers or dense gravel soil layers within the calculated depth range, the drilling depth may be reduced as appropriate.
3.2.3 The number of main and in-situ test exploration points and the amount of soil taken shall comply with the following provisions:
3.23.1 The number of soil taking and in-situ test exploration points shall account for 1/2 to 2/3 of the total number of exploration points, and a single building shall have at least two soil taking and in-situ test holes. 3.2.3.2 The original soil samples taken from the foundation bearing layer and the main load-bearing layer shall not be less than 6 pieces per layer, or the number of in-situ tests shall not be less than 6 times. 3.3 Indoor test and on-site in-situ test
The maximum pressure value applied by the indoor compression test shall be greater than the sum of the deadweight pressure and the expected additional pressure. The calculation of compression coefficient and compression modulus should be taken from the pressure section from the weight pressure to the sum of the electric weight pressure and the additional pressure. When the influence of unloading and reloading of deep foundation pit on foundation deformation needs to be considered, a rebound recompression test should be carried out, and the application of pressure should simulate the stress state of actual loading and unloading. 3.3.2 The shear test should adopt triaxial compression test. When the foundation is saturated soft or the load application rate is high, the triaxial unconsolidated undrained test method should be adopted. When the load application rate is low, the triaxial consolidated undrained test method should be adopted. 3.3.3 To determine the foundation bearing capacity and deformation calculation parameters of a first-class building or a building with special requirements, a flat plate load test should be carried out. The safety level of the building is divided according to the current national standard "Code for Design of Building Foundations" (GBJ7). 3.3.4 To determine the shear strength of the soft soil foundation, a cross-plate shear test should be carried out. 3.3.5 Static penetration and case pressure tests should be conducted to determine the uniformity, bearing capacity and deformation characteristics of clay, silt and sand.
3.3.6 Standard push penetration tests should be conducted to determine the density and earthquake liquefaction possibility of silt and sand.
3.3.7 Heavy or super heavy dynamic penetration tests should be conducted to determine the uniformity and bearing capacity of crushed stone soil.
3.3.8 Wave velocity tests should be conducted to obtain the parameters required for seismic design. 3.4 Groundwater
The groundwater level of the construction site should be determined, including the measured upper stagnant water, groundwater and confined water levels, seasonal variation range and the corrosiveness of groundwater to building materials. 3.4.2
For projects that require artificial lowering of the groundwater level, the survey report should include the site's hydrogeological data and the parameters of the dewatering design, make recommendations on dewatering methods, and conduct top-down measurements of the impact of dewatering on adjacent buildings and important underground facilities. Construction Standard Full Text Information System
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