GB 50007-2011Code for design of building foundation (English PDF)

1.0.1

This code is formulated with a view to implementing technical and economic policies of the nation in foundation design, and achieving safety and usability, advanced technology, economy and rationality, quality guarantee and environmental protection.

1.0.2

This code is applicable to the design of foundation of industrial and civil buildings (including structures). The design of collapsible loess, permafrost and expansive soil foundation and the foundation under the action of seismic and mechanical vibration load shall also meet the requirements of the current corresponding professional standard of the nation.

1.0.3

The design of foundation shall persist in the principle of adjusting measures to local conditions, using local materials, protecting environment and saving resources, comprehensively consider such factors as structure type, material condition and construction condition according to geotechnical engineering investigation data, and elaborately conduct.

1.0.4

The design of building foundation shall not only comply with this code, but also those in the current relevant ones of the nation.

2.1 Terms

2.1.1 Ground, foundation soils

Soil mass or rock mass which supports foundation.

2.1.2 Foundation

Structure component which transfers various actions borne by the structure to the ground.

2.1.3 Characteristic value of subsoil bearing capacity

Pressure value corresponding to deformation specified within linear deformation section of subsoil pressure deformation curve determined by load test, and its maximum value is the proportion limit value.

2.1.4 Gravity density, unit weight

Gravity borne by rock-soil mass per unit volume, the product of density and gravity acceleration of rock-soil mass.

2.1.5 Rock discontinuity structural plane

Plane which cracks and is easy to crack in rock mass, such as bedding surface, joint, fault, schistosity, etc., also called discontinuous structural plane.

2.1.6 Standard frost penetration

Average value of maximum frost penetration actually measured for more than 10 years in the flat and exposed open area outside the city.

2.1.7 Allowable subsoil deformation

Deformation control value determined in order to guarantee normal use of the building.

2.1.8 Soil-rock composite ground

Ground with larger underlying bed rock surface gradient within the range of main bearing layer of building ground; or ground with densely-spread and exposed clint; or ground with exposed mass boulder or individual clint.

2.1.9 Ground treatment, ground improvement

Engineering measures to be taken in order to increase subsoil bearing capacity or improve its deformability or permeability.

2.1.10 Composite ground, composite foundation

Artificial ground that subsoil and reinforcement formed by reinforcing or replacing partial soil mass jointly bear load.

2.1.11 Spread foundation

Foundation that spreads a certain base area to side edge in order to diffuse the load transmitted from superstructure to make the compressive stress acted on the base meet the design requirements of subsoil bearing capacity and the internal stress of foundation meet the design requirements of material strength.

2.1.12 Non-reinforced spread foundation

Strip foundation under wall or independent foundation under column, composed of such materials as brick, rubble, concrete or rubble concrete, dirt and cement and not reinforced.

2.1.13 Pile foundation

Foundation which is composed of pile arranged in rock-soil and slab connected to pile top end.

2.1.14 Retaining structure

Structure which is built to make rock-soil side slope remain stable, control displacement and mainly bear lateral load.

2.1.15 Excavation engineering

General term of retaining structure, underground water control, environmental protection and other measures required for guaranteeing underground space formed in downward ground excavation safe and stable during the construction period of underground structure.

2.2 Symbols

2.2.1 Action and action effect

Ea - - Active earth pressure;

Fk - - Value of vertical force, transferred from superstructure to foundation top, corresponding to the acting standard combination;

Gk - - Deadweight of foundation and soil weight on foundation;

Mk - - Value of moment acts on the foundation bottom, corresponding to the acting standard combination;

pk - - Average pressure at foundation bottom, corresponding to the acting standard combination;

p0 - - Average additional pressure at foundation bottom;

Qk - - Vertical force borne by single pile in pile foundation under the action of axial vertical force, corresponding to the acting standard combination.

2.2.2 Resistance and material property

a - - Compressibility coefficient;

c - - Cohesion strength;

Es - - Compression modulus of soil;

e - - Void ratio;

fa - - Corrected characteristic value of subsoil bearing capacity;

fak - - Characteristic value of subsoil bearing capacity;

frk - - Standardized value of uni-axial compressive strength of saturated rock;

qpa - - Characteristic value of soil bearing capacity of pile tip;

qsa - - Characteristic value of frictional force of pile periphery soil;

Ra - - Characteristic value of vertical bearing capacity of single pile;

w - - Moisture content of soil;

wL - - Liquid limit;

wp - - Plastic limit;

gamma - - Gravity density of soil, referred to as unit weight of soil;

delta - - Friction angle between fill and retaining wall back;

deltar - - Friction angle between fill and resistant rock slope surface;

theta - - Pressure diffusion angle of ground;

mu - - Friction coefficient between soil and retaining wall base;

v - - Poisson's ratio;

phi - - Internal friction angle.

2.2.3 Geometric parameters

A - - Foundation bottom area;

b - - Foundation bottom width (minimum side length); or foundation bottom side length of moment action direction;

d - - Embedded depth of foundation, pile body diameter;

h0 - - Foundation height;

Hf - - Building height counting from foundation bottom;

Hg - - Building height counting from outdoor ground;

L - - Building length or unit length separated by settlement joint;

l - - Length of foundation bottom;

s - - Settlement volume;

u - - Peripheral length;

z0 - - Standard frost penetration;

zn - - Calculation depth of ground settlement;

beta - - Slope angle of side slope to horizontal plane.

2.2.4 Calculation coefficient

- - Average additional stress coefficient;

etab - - Correction coefficient of bearing capacity of foundation width;

etad - - Correction coefficient of bearing capacity of embedded depth of foundation;

phis - - Empirical coefficient of settlement calculation.

3.0.1

The design of foundation shall be divided into three design grades according to ground complexity, building scale and functional characteristics as well as the degree of building damage or normal use influence caused by possible ground problems, and shall be selected in accordance with those specified in Table 3.0.1 according to specific conditions.

Table 3.0.1 Design Grade of Foundation

Design grade Building and ground type

Grade A Important industrial and civil buildings

High-rise buildings with more than 30 storeys

Combined high- and low-storey building with complicated shape and storey number difference exceeding 10

Extensive multi-story underground building (such as underground garage, shopping mall and sports ground)

Building with specific requirements for subsoil deformation

Building on slope (including high slope) under complicated geological conditions

Newly-built building with larger influence on existing engineering

General building with complicated site and ground conditions

Excavation engineering of basement of two-storey or above building in complicated geological conditions and soft soil area

Excavation engineering with excavation depth greater than 15m

Excavation engineering with complicated surrounding environment condition and high environmental protection requirements

Grade B Industrial and civil buildings beyond Grade A and Grade C

Excavation engineering beyond Grade A and Grade C

Grade C Seven-storey or below civil buildings and general industrial buildings with simple site and ground conditions and even load distribution; secondary light buildings

Excavation engineering in non-soft soil area, with simple site geological conditions, simple foundation pit surrounding environment conditions, not high environmental protection requirements and excavation depth less than 5.0m

3.0.2

The design of foundation shall meet the following requirements according to the design grade of building foundation and the influence degree of subsoil deformation under the action of long-term load on superstructure:

1 The foundation design calculation of all the buildings shall meet the relevant requirements for calculation of bearing capacity;

2 The buildings with a design grade of Grade A or Grade B shall be designed according to subsoil deformation;

3 The buildings with a design grade of Grade C shall be subjected to deformation checking under one of the following conditions:

1) Buildings with characteristic value of subsoil bearing capacity less than 130kPa and with complicated shape;

2) When there is ground loading on the foundation and neighborhood or the difference between the adjacent loads is large, and the ground may be caused to generate excessive nonuniform settlement;

3) When the building on soft ground has eccentric load;

4) When the adjacent buildings are close and may have inclination;

5) When there is relatively thick or uneven fill in ground and the deadweight consolidation is not completed.

4 For high-rise buildings, high-rise structure, retaining wall, etc. frequently subjected to horizontal load, as well as buildings and structures built on slope or near side slope, their stability shall also be checked;

5 Excavation engineering shall be subjected to stability checking;

6 When building basement or underground structure has floating upward problem, anti-floating checking shall also be conducted.

3.0.3

The buildings with a design grade of Grade C within the range listed in Table 3.0.3 may not be subjected to deformation checking.