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This code is developed by revising the original Guangdong provincial standard DBJ 15-31-2003 Design code for building foundation by Guangzhou Institute of Building Science, Architectural Design & Research Institute of SCUT, together with relevant design, investigation, construction, scientific research, teaching, inspection and supervision units according to the requirements of Notice on issuing the development and revision plan on engineering construction standards of Guangdong Province in 2014 (YUEJIANKEHAN [2014] No. 1384) issued by the Guangdong Provincial Department of Housing and Urban-Rural Development. The principle of this revision is to keep major issues in accordance with national standards and reflect the mature experience and technical progress in the design, investigation, construction, inspection and supervision of building foundation for more than ten years.
During the revision process, the code drafting group investigated and summarized the practical experience of building foundation engineering in Guangdong Province for more than ten years, carried out special studies, reasonably adopted some new study results, and extensively solicited opinions from relevant design, investigation, construction, inspection and quality supervision as well as scientific research and teaching units throughout the province, to finalize this code through repeated discussion, modification, trial design and review.
This code comprises 13 clauses and 11 annexes. The main revisions are as follows:
1. Division of foundation design grade and safety grade of foundation pit engineering.
2. Where the weathering degree of granite rocks is divided by the measured standard penetration number N ′, 40 ≤ N′ < 70 represents completely weathered, and N ′ ≥ 70 represents strongly weathered, which are consistent with the new geotechnical engineering investigation code.
3. The compressibility of soil is classified according to its compression modulus.
4. The definition of contaminated soil is added.
5. The contents of key geotechnical engineering investigation points are added.
6. The calculation principle for the uplift force and lateral pressure of groundwater on underground structures is specified.
7. The adjustment coefficient of wind-resistant bearing capacity of subgrade is specified.
8. The settlement calculation of overconsolidated or underconsolidated soil layers is added.
9. The reference table for effective reinforcement depth by dynamic compaction method is added.
10. The compaction criteria for various cushions and compacted fill are adjusted according to the actual engineering experience.
11. The bearing capacity revision coefficient of soil between piles in rigid pile composite subgrade is revised.
12. The section with saturated sandy soil overlying bedrock in karst development area is clearly defined as unstable site and is forbidden to be used as the bearing layer of composite subgrade.
13. The design method of rigid pile composite subgrade is added.
14. The calculation method of the shear capacity of spread foundation is added.
15. The calculation method of the flexural capacity of spread foundation is improved.
16. The resistance coefficient C1 at socketed pile end is adjusted from 0.3 ~ 0.5 to 0.4 ~ 0.6.
17. The characteristic value and description of pile side resistance of cast-in-situ bored pile with mud retaining wall in granite stratum are added.
18. The design method of post-grouting pile at pile bottom is added.
19. The calculation equations of the characteristic value of bond strength between rock bolt body and rock and the tensile bearing capacity at normal section of rock bolt are revised.
20. The quality inspection and acceptance methods of large-diameter socketed piles are revised.
21. It is specified that the pressure plate test of strongly-weathered rock shall be carried out according to the requirements of soil layer pressing plate test.
The provisions printed in bold type are compulsory provisions and must be enforced strictly.
Contents
1 General provisions 1
2 Terms and symbols 1
2.1 Terms 1
2.2 Symbols 4
3 Basic requirements 7
4 Geotechnical investigation 12
4.1 General requirements 12
4.2 Classification of rock and soil 14
4.3 Key points of geotechnical investigation 22
4.4 Engineering property indexes 31
4.5 Characteristic value of subgrade bearing capacity 35
4.6 Investigation report 39
5 Groundwater action 42
5.1 General requirements 42
5.2 Anti-floating design of basement 43
5.3 Groundwater control 46
6 Subgrade calculation 47
6.1 Buried depth of foundation 47
6.2 Bearing capacity calculation 48
6.3 Deformation calculation 56
6.4 Stability checking 65
7 Soft subgrade and ground treatment 66
7.1 General requirements 66
7.2 Utilization and treatment 67
7.3 Building measures 73
7.4 Structural measures 74
7.5 Large area ground load 76
7.6 Rigid pile composite subgrade 79
8 Special geology and foundation in mountainous area 83
8.1 General requirements 83
8.2 Soil-rock composite subgrade 84
8.3 Foundation on compacted fill 86
8.4 Landslide prevention 89
8.5 Karst and sinkhole 92
8.6 Side slope and retaining wall 95
9 Shallow foundation 103
9.1 Non-reinforced spread foundation 103
9.2 Spread footing 105
9.3 Strip footing under column 113
9.4 Raft foundation 115
10 Pile foundation 122
10.1 General requirements 122
10.2 Pile foundation design 130
10.3 Structure details of pile foundation 155
10.4 Seismic checking of pile foundation 158
10.5 Pile cap design 159
11 Foundation on rock-anchor system 163
11.1 General requirements 163
11.2 Uplift calculation for rock-anchor foundation 164
12 Retaining and protection for excavations 166
12.1 General requirements 166
12.2 Earth pressure and water pressure 170
12.3 Design calculation for retaining structure 171
12.4 Internal bracing of retaining structure 177
12.5 Soil nails and anchors 180
12.6 Reversed construction method 185
13 Inspection and monitoring 188
13.1 General requirements 188
13.2 Inspection 188
13.3 Monitoring 193
Annex A Key points for shallow plate load test 198
Annex B Key points for deep plate load test 200
Annex C Standard values of shear strength index, c and 202
Annex D Key points for rock subgrade load test 204
Annex E Key points for rock uniaxial compressive strength test 206
Annex F Key points for single-pile vertical compressive static load test 208
Annex G Key points for single-pile horizontal load test 212
Annex H Key points for single-pile vertical uplift static load test 215
Annex J Key points for rock anchor uplift test 218
Annex K Key points for pile side resistance test in bedrock 220
Annex L Key points for standard penetration, portable penetration, vane shear test and heavy dynamic penetration 223
Explanation of wording in this code 229
List of quoted standards 230
Design code for building foundation
1 General provisions
1.0.1 This code is formulated with a view to achieving safety, reliability, advanced technology, economic feasibility and environmental protection and to guaranteeing quality in the building foundation design in Guangdong Province.
1.0.2 This code is applicable to foundation design for industrial and civil buildings, including structures, in Guangdong Province.
1.0.3 This code is formulated according to the current national standards GB 50007 Code for design of building foundation and GB 50021 Code for investigation of geotechnical engineering, in combination with the geological conditions, engineering characteristics and engineering experience of Guangdong Province.
1.0.4 The foundation design shall be based on the foundation design grade and geotechnical engineering investigation data, by comprehensively taking into account factors such as structure type, construction conditions, construction cost, resource conservation and environmental protection, so as to be adaptive to local conditions, reasonable in type selection and well-designed.
1.0.5 In addition to those specified in this code, the building foundation design shall also comply with the requirements of the current relevant standards of the nation.
2 Terms and symbols
2.1 Terms
2.1.1
subgrade; foundation soils
soil or rock mass supporting the foundation
2.1.2
foundation
substructure transmitting various actions borne by the superstructure to the substructure of building on the subgrade
2.1.3
characteristic value of subgrade bearing capacity
pressure value corresponding to the specified deformation in the linear deformation section of the subsoil pressure deformation curve measured by load test, of which the maximum value is the proportional threshold value
2.1.4
revised characteristic value of subgrade bearing capacity
subgrade bearing capacity where the subsoil deformation does not exceed the allowable value under the condition of ensuring the subgrade stability
2.1.5
gravity density, unit weight
gravity borne by rock and soil per unit volume, which is the product of the density of rock and soil and the gravitational acceleration
2.1.6
rock discontinuity structural plane
cracked and easy-to-crack surface in rock mass, such as bedding, joint, fault and schistosity, which is also called discontinuous structural surface
2.1.7
allowable subsoil deformation
deformation control value set to ensure the normal use of building
2.1.8
soil-rock composite subgrade
subgrade with a large slope on the underlying bedrock surface; or subgrade with dense and exposed clints; or subgrade with exposed large boulder or individual clints within the scope of the main stress layer of the building foundation
2.1.9
ground treatment
engineering measure taken to increase the subgrade bearing capacity or improve its deformation or permeability
2.1.10
composite subgrade, composite foundation
artificial subgrade formed by reinforcing or replacing some soil so that the load is borne by both subsoil and reinforcement
2.1.11
spread foundation
foundation with a large bottom area formed by the outward expansion of support cross-section at the root of column and wall, which spreads large compressive stress from the superstructure, so that the compressive stress acting on the foundation meets the design requirements of the subgrade bearing capacity
2.1.12
non-reinforced spread foundation
strip foundation under wall or independent foundation under column, composed of brick, rubble, concrete or rubble concrete, lime soil and trinity mixture fill
2.1.13
strip foundation, strip footing
strip foundation under a wall or column
2.1.14
raft foundation, mat foundation
reinforced concrete slab or ribbed slab foundation supporting the load of the whole structure and having an area not less than the floor area of the building
2.1.15
pile foundation
foundation consisting of a pile socketed in rock and soil and a cap connected to the top of the pile
2.1.16
socketed pile
pile partly entering the rock at the lower part and supported by moderately-weathered and weakly-weathered rock layer
2.1.17
retaining structure
structure built to keep the rock and soil side slope stable, control the displacement, and mainly bear lateral loads
2.1.18
hard rock
rock with saturated uniaxial compressive strength greater than 30MPa
2.1.19
weak rock
rock with saturated uniaxial compressive strength less than or equal to 30MPa
2.1.20
bearing layer, sustaining layer
stratum directly bearing foundation load
2.1.21
compressed layer
generic term of soil layer within the foundation settlement calculation depth
2.1.22
underlying layer
each soil layer located below the bearing layer of the structure foundation and within the range of compression layer
2.1.23
punching failure
continuous sinking failure mode of the foundation caused by the compressive deformation and lateral extrusion of the bearing layer under the foundation load, making the foundation cut into the soil
2.1.24
cushion
sand, gravel, lime soil or plain soil layer, etc. with certain thickness, which is filled on soft subsoil or replaces the upper part of the soft subsoil
2.1.25
softening coefficient of rock
ratio of uniaxial compressive strength of rock in saturated state to uniaxial compressive strength in dry state
2.2 Symbols
A——Area of foundation bottom;
Ap——Sectional area of pile;
a——Compression coefficient;
b——Width of foundation bottom (minimum side length) or side length of the foundation bottom in the moment action direction;
c——Cohesion;
ck——Standard value of soil cohesion;
D——Diameter of pile end enlarged bottom;
d——Foundation buried depth or pile diameter;
Ea——Active soil pressure;
Es——Compressive modulus of soil;
E0——Deformation modulus of soil;
e——Void ratio;
F——Vertical force on the top surface of foundation;
Fk——Vertical force acting on the top surface of foundation in the standard combination of loads;
fa——Revised characteristic value of subgrade bearing capacity, or characteristic value of bearing capacity of rock subgrade;
fak——Characteristic value of subgrade bearing capacity;
frk——Standard value of saturated uniaxial compressive strength of rock;
faz——Characteristic value of subgrade bearing capacity on the top of soft underlying layer;
G——Dead load;
Gk——Standard value of the dead weight of foundation and the weight of soil on the foundation;
H0——Foundation height;
Hf ——Building height calculated from the bottom of foundation;
Hg——Building height calculated from the ground;
L——Length of house or unit length separated by settlement joint;
l——Length of foundation bottom;
M——Design value of the moment acting on the foundation bottom or bending moment of the section;
Mk——Standard value of the bending moment acting on the foundation bottom or bending moment of the section;
Mb, Md, Mc——Bearing capacity coefficient;
m——Proportionality coefficient of soil horizontal resistance coefficient;
N——Revised blow count of standard penetration test;
N′——Measured blow count of standard penetration test;
N63.5——Revised blow count of heavy dynamic penetration test;
——Measured blow count of heavy dynamic penetration test;
n——Number of piles;
pk——Average pressure on foundation bottom in the standard combination of load effects;
p0——Average additional pressure on foundation bottom in the standard combination of load effects;
pz——Additional stress on foundation bottom in the standard combination of load effects;
pcz——Deadweight pressure of soil on the top surface of the weak underlying layer;
Qk——Vertical load in the standard combination of load effects and vertical force borne by a single pile in the pile foundation;
qpa——Characteristic value of the bearing capacity of pile tip soil;
qsa——Characteristic value of the friction of soil around the pile;
Ra——Characteristic value of the vertical bearing capacity of a single pile;
RHa——Characteristic value of singe pile horizontal bearing capacity;
Rta——Characteristic value of singe pile uplift bearing capacity;
St——Sensitivity of soil;
s——Settlement;
u——Peripheral length;
up——Peripheral length of pile body;
W——Resistance moment of foundation bottom;
w——Water content of soil;
wL——Liquid limit;
wp——Plastic limit;
z——Depth from the loading surface of the foundation bottom;
zn——Calculated depth of foundation settlement;
β——Slope angle of the side slope to the horizontal plane;
γ——Gravity density of soil, which is referred to as unit weight;
γm——Weighted mean unit weight of each soil layer in the buried depth of foundation; the effective unit weight shall be taken below the groundwater level;
——Internal friction angle;
δ——Friction angle of soil against the back of retaining wall;
μ——Friction coefficient of soil against the base of retaining wall;
ηb——Revision coefficient of bearing capacity for foundation width;
ηd——Revision coefficient of bearing capacity for foundation buried depth;
θ——Subgrade pressure diffusion angle;
v——Poisson's ratio of soil;
ψf——Regression revision coefficient;
ψs——Empirical coefficient of settlement calculation;
, ——Average additional stress coefficient from calculation point of foundation bottom to bottom of the ith layer of soil and the i-1th layer of soil.
3 Basic requirements
3.0.1 According to the complexity of subgrade, the scale and characteristics of buildings, and the degree of damage or influence on the normal use of buildings due to foundation problems, the foundation design is classified into three grades, which shall be selected according to the specific conditions in the design as per Table 3.0.1.
Table 3.0.1 Foundation design grade
Design grade Type of building and subgrade
Grade A Important industrial and civil buildings;
High-rise buildings above 30 storeys;
Buildings with complex shapes formed by high building and low building connected to each other with the high one 10 storeys more than the low one;
Large-area multi-storey underground buildings (such as underground garages, shopping malls and sports fields);
Buildings with special requirements for subsoil deformation;
Buildings on slopes under complex geological conditions (including high side slopes);
New buildings which have great influence on adjacent buildings;
General buildings with complex site and foundation conditions.
Grade B Industrial and civil buildings other than those of grades A and C
Grade C Civil or general industrial buildings with 7 storeys or less and with simple site and foundation conditions and uniform load distribution; minor light buildings
3.0.2 According to the building foundation design grade and the influence degree of foundation deformation on superstructure under the action of long-term load, the foundation design shall meet the following requirements:
1 The subgrade calculation of all buildings shall meet the relevant requirements of bearing capacity calculation.
2 Buildings with foundation of design grade A and grade B shall be subjected to subgrade deformation calculation.
3 Deformation checking shall be carried out for buildings of design grade C under any of the following circumstances:
1) The characteristic value of subgrade bearing capacity is less than 130kPa, and the building is complex.
2) Where there are ground heaps on the foundation or near the foundation, or where the foundation load differs greatly from that of its adjacent foundation, and may cause excessive uneven settlement of the ground.
3) Where eccentric load exists in buildings on soft foundation.
4) Where adjacent buildings are close to each other and there is possibility for the building to tilt.
5) Where there is filling with large thickness or uneven thickness in the subgrade but its dead weight consolidation is not finished yet.
4 For high-rise building, high-rise structure and retaining wall frequently affected by horizontal load and building & structure built on slope or near side slope, the stability shall also be checked.
5 Stability checking shall be carried out for foundation pit engineering.
6 If there is floating problem in building basement or underground structures, anti-floating checking shall be carried out.
3.0.3 Deformation checking may not be carried out for the following buildings:
1 Building with the shallow foundation bearing layer of moderately- and weakly-weathered rock; building less than fifteen storeys, with strip or raft foundation, and the bearing layer of gravel soil, dense sand, hard plastic to hard residual soil layer or completely-weathered and strongly-weathered rock layer with characteristic value of subgrade bearing capacity ≥300kPa; building with pile foundation and the bearing layer of moderately-weathered rock layer; or building less than 30 storeys and the pile foundation bearing layer of medium-dense sand layer, egg layer and gravel layer (without weak underlying layer), hard plastic to hard residual soil, completely-weathered and strongly-weathered rock layer.
1 General provisions
2 Terms and symbols
2.1 Terms
2.2 Symbols
3 Basic requirements
4 Geotechnical investigation
4.1 General requirements
4.2 Classification of rock and soil
4.3 Key points of geotechnical investigation
4.4 Engineering property indexes
4.5 Characteristic value of subgrade bearing capacity
4.6 Investigation report
5 Groundwater action
5.1 General requirements
5.2 Anti-floating design of basement
5.3 Groundwater control
6 Subgrade calculation
6.1 Buried depth of foundation
6.2 Bearing capacity calculation
6.3 Deformation calculation
6.4 Stability checking
7 Soft subgrade and ground treatment
7.1 General requirements
7.2 Utilization and treatment
7.3 Building measures
7.4 Structural measures
7.5 Large area ground load
7.6 Rigid pile composite subgrade
8 Special geology and foundation in mountainous area
8.1 General requirements
8.2 Soil-rock composite subgrade
8.3 Foundation on compacted fill
8.4 Landslide prevention
8.5 Karst and sinkhole
8.6 Side slope and retaining wall
9 Shallow foundation
9.1 Non-reinforced spread foundation
9.2 Spread footing
9.3 Strip footing under column
9.4 Raft foundation
10 Pile foundation
10.1 General requirements
10.2 Pile foundation design
10.3 Structure details of pile foundation
10.4 Seismic checking of pile foundation
10.5 Pile cap design
11 Foundation on rock-anchor system
11.1 General requirements
11.2 Uplift calculation for rock-anchor foundation
12 Retaining and protection for excavations
12.1 General requirements
12.2 Earth pressure and water pressure
12.3 Design calculation for retaining structure
12.4 Internal bracing of retaining structure
12.5 Soil nails and anchors
12.6 Reversed construction method
13 Inspection and monitoring
13.1 General requirements
13.2 Inspection
13.3 Monitoring
Annex A Key points for shallow plate load test
Annex B Key points for deep plate load test
Annex C Standard values of shear strength index, c and
Annex D Key points for rock subgrade load test
Annex E Key points for rock uniaxial compressive strength test
Annex F Key points for single-pile vertical compressive static load test
Annex G Key points for single-pile horizontal load test
Annex H Key points for single-pile vertical uplift static load test
Annex J Key points for rock anchor uplift test
Annex K Key points for pile side resistance test in bedrock
Annex L Key points for standard penetration, portable penetration, vane shear test and heavy dynamic penetration
Explanation of wording in this code
List of quoted standards
