1 General Provisions
1.0.1 This code is formulated with a view to implement the national technical and economical policies in design of the building grounds, foundations, that the design can be accomplished with safety and usability, using advanced technology, with economy and rationality, assuring the quality and protecting the environment.
1.0.2 Design of the building grounds, foundations must persist in the principles of suiting measures to local conditions, using local materials, protecting the environment and economizing on the resources; the design shall be painstakingly performed, considering the factors comprehensively as the type of structures, the availability of materials and the construction conditions etc., according to the geotechnical survey data of rocks, soils.
1.0.3 This code is applicable to the design of grounds, foundations of industrial and civilian buildings (including structures). For the design of grounds, foundations in the collapsible loess, the perennial frozen soil and the swelling soil, as well as, under the action of seismic load and vibrating load of machines, that the requirements in the current relevant standards or codes of the nation shall also be complied with.
1.0.4 This code is formulated according to the basic principles of national standard Unified Standards for the Design of Structures (GBJ 68-84) and the requirements of national standard Design of Structures — General Symbols Units of Measurement and Basic Terms (GBJ 83-85).
1.0.5 When this code is used for design, the values of loads shall meet the requirements in the current National Standard Load Code for the Design of Building Structures (GBJ 9-87); the calculation of foundations shall also meet the requirements of the National Standard Code for Design of Concrete Structures (GBJ 10-89) and Code for Design of Masonry Structures (GBJ 3-88). When the foundations are laid in aggressive environment or are subjected to temperature influence, that the requirements in the current relevant mandatory standard of the nation shall also be complied with, and the corresponding protective measures shall be taken.
2 Basic Requirement
2.0.1 According to the severity degree for being possible to destroy buildings (endanger person life, result in economic loss and social influence, as well as the possibility of restoration), hence, the design of grounds, foundations are divided into three design classes, which shall be selected for design from Table 2.0.1, according to the specific conditions.
Table 2.0.1 Design Classes for Grounds, Foundations
Design classes Consequence Categories of buildings and grounds
Class I Very serious Important industrial and civilian buildings; Tall buildings with more than 20 stories; Complicated shaped high buildings more than 14 stories; Buildings with special requirements for deformation of ground; Buildings of single pile subjected to loads above 4000kN
Class II Serious General industrial and civilian buildings
Class III Not serious secondary buildings
2.0.2 According to the design classes of ground, foundation, as well as, the degree of influence on the upper structure due to the deformation of ground under the effects of long-term loading, hence, the design of ground, foundation shall meet the following require-meats:
I The deformation design of ground shall be performed for the buildings belong to Class I, Class II (except those specified in Table 2.0.2); the calculation shall simultaneously meet the requirements of 6.2.1 and 5.1.1 of this code;
II The buildings for design Class III with the scope listed in Table 2.0.2, that the checking computation of deformation may not be performed, if one of the following situations occurs, the checking computation of deformation shall still be performed:
1. The standard value for load-bearing capacity of ground for building is less than 130kPa, and with the complicated shape building;
2. The ground stacking load is acted on the foundations and in the vicinity of foundations or the difference of loadings on the neighboring foundations is quite large, when it may possible arouse the large unequal settlements of ground;
3. When the tilting of building may be occurred, if the distance between the neighboring buildings on the soft weak soil ground are too closer;
4. When there exists the earth-fill with comparative great thickness or the earth-fill with non-uniform thickness, its self-weight consolidation has not been completed.
Deformation check of Classes II and III buildings at other conditions is not compulsory, provided that meet the requirements of Clause 5, subclause 1.
III For the tall buildings, the high-rise structures sustain the effects of horizontal loading frequently, as well as, the buildings and the structures are constructed on the inclined slope or near the side slope, their stability shall also be checking computed;
Table 2.0.2 Scope for Buildings of Design Class III, Which the Calculation for Deformation of Ground may not be Performed
Conditions for main bearing stratum of ground Standard value for load-bearing capacity of ground fak (kPa) 60≤fak<80 80≤fak<100 100≤fak<130 130≤fak<160 160≤fak<200 200≤fak<300
Gradient of each soil stratum (%) ≤5 ≤5 ≤10 ≤10 ≤10 ≤10
Type of building Masonry load-bearing structure, Frame structure (number of stories) ≤5 ≤5 ≤5 ≤6 ≤6 ≤7
Single story bent frame structure (6m span between columns) Single span Rated hoisting capacity (t) of crane 5~10 10~15 15~20 20~30 30~50 50~100
Span of factory
building (m) 412 418 424 430 430 430
Multi-span Rated hoisting capacity (t) of crane 3~5 5~10 10~15 15~20 20~30 30~75
Span of factory building (m) ≤12 ≤18 ≤24 ≤30 ≤30 ≤30
Chimney Height (m) ≤30 ≤40 ≤50 ≤75 ≤100
Water tower Height (m) ≤15 ≤20 ≤30 ≤30 ≤30
Volume (m3) ≤50 50~100 100~200 200~300 300~500 500~1000
Notes:
1 The main bearing stratum of ground denotes the scope of stratum with a depth of 3b (b is the width of foundation base surface) beneath the base surface of strip foundation, with a depth of 1.5b beneath the base surface of independent foundation, and their scope of thickness are not less than 5m (besides the general civilian buildings under two stories);
2 When the standard value for load-bearing capacity of soil stratum is less than 130kPa, in the main bearing stratum of ground, hence, the design of masonry structure, as specified in Table, shall meet the relevant requirements in Clause 7 of this code;
3 The masonry load-bearing structure and the frame structure in Table denote the civilian buildings, for the industrial building may be converted into the corresponding number for stories of civilian building, according to the height of factory building and the loading conditions;
4 The values of the rated hoisting capacity of crane, the height of chimney and the volume of water tower in Table, denote their maximum values.
2.0.3 When according to the load-bearing capacity of ground to determine the base area of foundation and the depth of embedment to determine the number of piles, that the load-effects, which are transmitting to the base surface of foundation, shall be calculated by using basic combination, soil mass deadweight partial coefficients 1.0 and actual gravimetric density.
To calculate the foundation deformation, long term effect combination shall be adopted for the load effect transmitted to the foundation base which shall not be counted into wind load and earthquake action.
When calculating the earth pressure of retaining wall, the stability of ground or slope, as well as, the thrust of landslide, that the load-effects shall comply with the fundamental combination, but their partial coefficients are 1.0.
2.0.4 For Class I buildings, settlement observation shall be carried out at construction period and service period, and the measured data shall be served as one of the reference of foundation work quality inspection of building grounds. The methods and requirements of settlement observation shall be in accordance with Annex 1 of this code.
3 Classification of Geotechnical Rocks, Soils and Their Engineering Property Indexes
3.1 Classification of Rocks, Soils
3.1.1 The rock, soil, which are used for the grounds of buildings, may be classified into rock, gravelly soil, sandy soil, silty soil, cohesive soil and artificial earth-fill.
3.1.2 The rock shall be the rock mass with firmly joining between its particles and showing as a whole or as possessed some fissures at its joints. The hardness of rocks are classified into hard rock and weak rock. The weathering degree of rocks may be classified into fresh, slightly weathered, moderately weathered and highly weathered. Rocks may be comply with the Annex 2 of this code.
3.1.3 The broken stone soil means that the content of grains with its diameter larger than 2mm are exceeding 50% of the total weight of soil. The broken stone soil may be classified into boulder, block stone, cobble, broken stone, rounded gravel and angular gravel, according to Table 3.1.3.
Table 3.1.3 Classification of Broken Stone soils
Name of soil Shape of grain Content of grains set
Boulder Block stone Rounded shape and sub-rounded shape are predominant
Aries shape is predominant Content of grains with its diameter greater than 200mm are exceeding 50% of the total weight of soil
Cobble Broken stone Rounded shape and sub-rounded shape are predominant
Aries shape is predominant Content of grains with its diameter than 20mm are exceeding 50% of the total weight of soil
Rounded gravel
Angular gravel Rounded shape and sub-rounded shape are predominant
Aries shape is predominant Content of grains with its diameter greater than 2mm are exceeding 50% of the total weight of soil
Note: When classifying the broken stone soil shall accord to the content of grains set column from top to bottom, it is determined by the first conformable one.
3.1.4 The sandy soil means that the content of grains with its diameter larger than 2mm is not exceeding the 50% of total weight of soil, with its diameter larger than 0.075mm is exceeding the 50% of total weight of soil. The sandy soil may be classified into gravelly sand, coarse sand, medium sand, fine sand and silty sand, according to Table 3.1.4.
Table 3.1.4 Classification of Sandy Soils
Name of soil Content of grains set
Gravelly sand Content of grains with its diameter larger than 2mm amounts to 25%~50% of total weight of soil
Coarse sand Content of grains with its diameter larger than 0.5mm is exceeding the 50% of total weight of soil
Medium sand Content of grains with its diameter larger than 0.25mm is exceeding the 50% of total weight of soil
Fine sand Content of grains with its diameter larger than 0.075mm is exceeding the 85% of total weight of soil
Silty sand Content of grains with its diameter larger than 0.075mm is exceeding the 50% of total weight of soil
Note: When classifying the sandy soil shall accord to the content of grains set column from top to bottom, it is determined by the first conformable one.
3.1.5 The density of sandy soil may be classified into loose, slightly dense, medium dense and dense, according Table 3.1.5.
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Table 3.1.5 Density of Sandy Soil
Blow count from standard penetration test N Density
N≤10 Loose
1030 Dense
Note: When the density of sandy soil is judged by the obstructive force of static probing head, it may be determine according to the locality experience.
3.1.6 The cohesive soil, which is the soil with the plasticity index Ip larger than 10, may be classified into clay, silty clay, according to Table 3.1.6.
Table 3.1.6 Classification of Cohesive Soils
Plasticity index Ip Name of soil
Ip>17 Clay
101 Fluid plastic
Note: When the blow count from the obstructive force of static probing head or the standard penetration test is used to judge the states of cohesive soil, it may be determined according to with the locality experience.
3.1.8 The mud is formed by the deposition in the stagnant water or the slowly flowing water environment, and through the biochemical reaction, its natural moisture content is larger than the liquid limit, and the natural void ratio is larger or equal to 1.5 of the cohesive soil. When the soil with the natural void ratio is less than 1.5, but it is larger than or equal to 1.0, hence, it belongs to muddy soil.
3.1.9 The laterite belongs to high plasticity clay, which is formed from carbonate series rock through the action of laterization, its liquid limit is usually larger than 50. The basic features of laterite will be reserved after transporting repeatedly, when the liquid limit of laterite is larger than 45, hence, it belongs to secondary laterite.
3.1.10 Silty soil shall be the soil with plasticity index less than or equal to 10. Their properties are between sandy soil and clay soil.
3.1.11 The artificial earth-fill may be classified into plain earth-fill, miscellaneous earth-fill and flushing earth-fill according to their composition and the cause of formation.
The plain earth-fill is the fill composed by broken stone soil, sandy soil, silty soil, cohesive soil etc. The miscellaneous earth-fill is the fill contained the impurity substances including the building refuse, the industrial waste materials, the living garbage etc. The flushing earth-fill is the fill formed by hydraulic flushing filled silts.
3.2 Engineering Property Indexes
3.2.1 When standard value of ground bearing capacity determined by load test, the area of press plate should be0.25~0.50m2, the load test shall meet the requirements specified in Annex 4 of this code.
3.2.2 Standard value for the bearing capacity of ground soil and rock determined by indoor test, standard penetration test, portable penetration sounding or field identification method, the methods and procedures shall comply with the provisions of Annex 5 of this code, in statistical data of not less than six. Standard penetration and portable penetration tests shall comply with the requirements of Annex 6 of this code.
3.2.3 When the standard value or other soil indexes of ground bearing capacity are determined by static sounding, pressuremeter and other in-situ tests, the results shall be determined after comparison with the direct test results of load tests or corresponding soil indexes.
3.2.4 The shearing strength index of soil may be determined by the test methods including: the laboratory shear test of undisturbed soil specimen, the compression strength without lateral pressure test, the shear test in situ, the vane shear test etc., and shall meet the following requirements:
1 For Class I buildings, when indoor shearing test is adopted, earth-borrowing holes shall not be less than six. For uniform soil, drilling holes at the same soil layer along the depth test shall not be less than three sets; when the multilayer and thin soil, the test shall not be less than one set, the unconsolidated, undrained test in the triaxial compression test shall be selected; for other buildings, direct shear test may be adopted for castable clay soil and silty soil of saturation not greater than 0.5.
2 If consolidated shearing tests are taken, the extent to which the foundation may be consolidated under the action of building load and preloading load shall be taken into account.
The standard value of shearing strength indexes may be determined according to Appendix 7 of this code.
3.2.5 The design value of bearing capacity of rock foundation, may be determined according to the test methods for batholite load specified in Annex 8 of this code. The design value of bearing capacity of rock foundation with slight weathering and moderate weathering, can also be calculated according to the saturated uniaxial compressive strength by using the formula below:
Main Symbols
1 General Provisions
2 Basic Requirement
3 Classification of Geotechnical Rocks, Soils and Their Engineering Property Indexes
3.1 Classification of Rocks, Soils
3.2 Engineering Property Indexes
4 Embedded Depth of Foundation
4.1 General provisions
4.2 Embedded Depth of Foundation and Treatment of Frozen Soil Ground
5 Calculation of Ground
5.1 Calculation of Load-bearing Capacity
5.2 Calculation of Deformation
5.3 Calculation of Stability
6 Ground in Mountainous Region
6.1 General Requirement
6.2 Soil-rock Composite Ground
6.3 Compacted Fill Ground
6.4 Side Slope and Retaining Wall
6.5 Landslide Prevention
6.6 Karst and Earth Cave
7 Feeble Ground
7.1 General Requirement
7.2 Utilization and Treatment
7.3 Architectural Measures
7.4 Structural Measures
7.5 Large Area Ground Surface Load
8 Foundations
8.1 Rigid Foundation
8.2 Spread Foundation
8.3 Strip Footing under Columns
8.4 Raft Foundation under Wall
8.5 Shell Foundation
8.6 Pile Foundation
8.7 Rock Anchored Bolt Foundation
Annex 1 Main Points for Settlement Observation
Annex 2 Division of Rock
Annex 3 Field-distinction of Broken Stone Soil
Annex 4 Main Points of Ground Soil Load Test
Annex 5 Standard value for the Bearing Capacity of Soil (Rock)
Annex 6 Main Points of Standard Penetration and Light Penetration Tests
Annex 7 Standard value of Shear Strength Indexes c, φ
Annex 8 Main Points for Loading Test of Rock Ground
Annex 9 Main Points for Uniaxial Compression Strength Test of Rock
Annex 10 Coefficient of Additional Stress α and Coefficient of Average Additional Stress
Annex 11 Coefficient of Active Earth Pressure ka for Retaining Wall
Annex 12 Calculation for Additional Settlement Amount of Ground under the Action of Large Area Ground Surface Load
Annex 13 Internal Force Formulae of Film Theory of Shell Foundation
Annex 14 Main Points for Vertical Static Loading Test of Single Pile
Annex 15 Standard value of Vertical Bearing Capacity of Precast Pile
Annex 16 Explanation of Wording in This Code
