This code is formulated to achieve advanced technology, economic rationality, and ensure the stability of the foundation pit slope and the safety of buildings, roads and underground facilities around the foundation pit in the design and construction of building foundation pit support. The code is applicable to the engineering survey, support design, construction, testing, foundation pit excavation and monitoring of buildings and general structures under general geological conditions. For areas with special geological conditions such as expansive soil and collapsible loess, it should be applied in combination with local engineering experience. JGJ 120-1999 Technical Code for Building Foundation Pit Support JGJ120-1999 Standard download decompression password: www.bzxz.net

Engineering Construction Standard Full-text Information System
Industry Standard of the People's Republic of China
Technical Specification for Retaining and Protection of Building Foundation Excavations JGJ120—99
1999 Beijing
Engineering Construction Standard Full-text Information System
Engineering Construction Standard Full-text Information System
Industry Standard of the People's Republic of China
Technical Specification for Retaining and Protection of Building Foundation Excavations of Building Foundation Excavations JGL12099
Editing Unit: China Academy of Building ResearchApproving Department: Ministry of Construction of the People's Republic of ChinaEffective Date: September 1, 1999
1999 Beijing
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Notice on Issuing Industry Standard
"Technical Code for Building Foundation Excavations"Construction Standard [1999] No. 56
According to the requirements of the Ministry of Construction's "Notice on Issuing the 1995 Urban Construction and Construction Engineering Industry Standard Promotion and Formulation and Revision Project Plan (Second Batch)" (Construction Standard [1995] No. 661), the "Technical Code for Building Foundation Excavations" edited by the China Academy of Building Research has been reviewed and approved as a mandatory industry standard, with the number JGJ12099, and will be implemented on September 1, 1999.
This standard is managed by the China Academy of Building Research, the technical unit responsible for building engineering standards under the Ministry of Construction, and is responsible for specific interpretation. It is published by the China Building Industry Press organized by the Standard and Norms Research Institute of the Ministry of Construction. Ministry of Construction of the People's Republic of China
March 4, 1999
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
This specification is formulated based on the document No. 661 of the Ministry of Construction of the People's Republic of China.
This specification has eight chapters, and the main technical contents include: general principles, terms, symbols, basic regulations, pile rows, underground continuous walls, cement soil walls, soil nail walls, top arch walls, groundwater control, etc.
This specification is managed by the China Academy of Building Research, the technical unit responsible for building engineering standards under the Ministry of Construction (No. 30, North Third Ring Road East, Beijing: Postal Code 100013), and is responsible for specific interpretation.
Editor: China Academy of Building Research Participating Units: Shenzhen Survey and Research Institute
Fujian Academy of Building Research
Tongji University
Architectural Research Institute of Ministry of Metallurgy
Guangzhou Academy of Building Research
Jiangxi New Dadi Construction Supervision Company
Beijing Survey and Design Institute
The Third Survey and Research Institute of Ministry of Machinery
Shenzhen Engineering Quality Supervision and Inspection Center
Chongqing Architectural Design Institute
Zhaoqing Construction Engineering Quality Supervision Center
Drafting Person: Huang Qiang, Yang Bin, Li Rongqiang, Hou Weisheng, Yang Min, Yang Zhiyin, Chen Xinyu, Chen Rugui
Liu Xiaomin
Liu Jinli
Wang Tiehong
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Hu Jianlin
Wei Zhanghe
Zheng Shengqing|| tt||Bai Shengxiang
Li Zixin
Zhang Changding
Zhang Zaiming
Li Ruiru
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Terminology Symbols
2.2 Symbols
Basic Provisions
Design Principles
3.2 Survey Requirements
Support Structure Selection
Water Standard value of horizontal load
Standard position of horizontal resistance
Quality inspection
.....6
Foundation pit excavation
Excavation monitoring
4 Rows of piles, underground continuous wall
4.1 Calculation of embedded depth
4.2 Structural calculation
4.3 Calculation of cross-section bearing capacity
4.4 Pole laying calculation
4.5 Calculation of support system||t t||4.6 Structure
Construction and testing
5 Cement king wall
5.1 Calculation of embedding depth
5.2 Calculation of wall thickness
5.3 Verification of normal section bearing capacity
5.4 Meixi
5.5 Construction and testing
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Soil nail wall||tt| |#中中中中
6.1 Calculation of tensile bearing capacity of soil nails
6.2 Verification of overall stability of soil nail wall
.3 Structure
6.4 Construction and testing
Reverse arch wall
7.1 Calculation of arch wall
7.2 Structure
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Construction and testing
Groundwater control
Appendix A
Appendix
Appendix
Appendix D
Appendix E
Appendix F
Appendix G
-General Provisions
Open drainage for water collection
Simple strip method for circular sliding
Elastic support method
.........
Horizontal stiffness coefficient of support and proportional coefficient of horizontal resistance of foundation soil m
Calculation of bending bearing capacity of positive section
Anchor test
Calculation of water inflow from foundation pit
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Engineering Construction Standard Full-text Information System
This code is formulated to achieve advanced technology and economic rationality in the design and construction of building foundation pit support and ensure the stability of foundation pit slopes and the safety of buildings, roads and underground facilities around the foundation pit.
1.0.2 This code is applicable to the engineering survey, support design, construction, inspection, excavation and monitoring of foundation pits for buildings and general structures under general geological conditions. For areas with special geological conditions such as expansive soil and collapsible loess, it should be applied in combination with local engineering experience. 1.0.3 The design and construction of foundation pit support should comprehensively consider factors such as engineering geology and hydrogeology conditions, foundation type, foundation pit excavation depth, drainage conditions, requirements of the surrounding environment on the displacement of the foundation pit side wall, loads around the foundation pit, construction season, and the service life of the support structure, so as to adapt to local conditions and time, and reasonably design, carefully construct, and strictly monitor. 1.0.4
In addition to complying with the provisions of this code, the foundation pit support project shall also comply with the provisions of the relevant national standards, specifications and regulations currently in force. Engineering Construction Standard Full Text Information System
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2 Terms and Symbols
2.1 Terms
2..1 Building foundation pit is the space below the ground excavated for the construction of the foundation and basement of the building (including the structure).
2.1.2 Sidewall of foundation pit constitutes one side of the building foundation pit enclosure. 2.1.3 Surroundings around foundation pit is a general term for the existing buildings (structures), roads, underground facilities, underground pipelines, rock and soil bodies and groundwater bodies within the scope of influence of foundation pit excavation. 2.1.4
vation
retaining and protecting for foundation pit-retaining, reinforcement and protection measures for the sidewalls of foundation pit and the surrounding environment to ensure the safety of underground structure construction and the surrounding environment of foundation pit. 2.1.5 Piles in row
A certain type of piles arranged in a queue. 2.1.6
Diaphragm
An underground wall formed by pouring reinforced concrete in a trench by mechanical construction. 2.1.7 Cement-soil wall A gravity structure in the form of a grid or wall formed by overlapping cement-soil piles.
Soil nailing wall
A support structure consisting of the soil and the face of the foundation pit reinforced by soil nails. 2..9Soil anchor
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A tension rod composed of a steel bar or steel strand set in a drilled hole with its end extending into the stable soil layer and a grouting body in the hole.
2.1.10Bracing system
A structural system composed of steel or reinforced concrete components used to support the side walls of the foundation pit.
2.1.11Top beam
A reinforced concrete connecting beam set at the top of the supporting structure2.1.12Middle beam
A reinforced concrete beam or steel beam set below the top of the supporting structure to transfer the supporting structure and the anchor or internal support support force.
2.1.13Fulcrum
The horizontal constraint point of the anchor or bracing system on the supporting structure. Stiffness coefficient of full curve - 2.1.14
The ratio of the horizontal reaction force of the paving pole or support system on the supporting structure to its displacement.
Embedded depth
The depth of the pile wall structure below the bottom of the foundation pit excavation. 2.1.16 Design value of embedded depth Design value of embedded depth The design value of the embedded depth of the supporting structure determined according to the safety level of the foundation pit side wall and the verification conditions of the supporting structure.
2.1.17 Groundwater control Drainage, precipitation, water interception or recharge measures taken to ensure the safety of the supporting structure construction, foundation pit excavation, basement construction and the surrounding environment of the foundation pit. 2.1.1 Curtain for cutting off water A continuous water stop used to intercept or reduce the inflow of groundwater from the side walls and bottom of the foundation pit into the foundation pit.
2.2 Symbols
2.2.1 Resistance and material properties
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——Standard value of soil cohesion;
——Standard value of soil internal friction angle;
——Porosity ratio of soil;
k——Permeability coefficient of soil;
femkfem
fykfpyk
fpy,bzxZ.net
——Natural water content of soil,
Gravity density of soil (referred to as soil gravity); Water-concrete Average weight of earth wall
Standard value and design value of axial compressive strength of cement soil at excavation age; Proportional coefficient of horizontal resistance coefficient of foundation soil; Standard value and design value of axial compressive strength of concrete; Standard value and design value of bending compressive strength of concrete; Standard value of tensile strength of ordinary steel bars and prestressed steel bars; Design value of tensile and compressive strength of ordinary steel bars; Design value of tensile and compressive strength of prestressed steel bars: Standard value of horizontal resistance at 3 points below the excavation surface of foundation pit; Passive earth pressure coefficient of the i-th layer of soil;
Support stiffness coefficient (spring) coefficient of the support point; Spring coefficient of soil below the excavation surface of foundation pit; Design value of axial tensile bearing capacity of anchor rod.
2.2.2 Action and effect of action
Standard value of horizontal load at point i:
Ka——Active earth pressure coefficient of the i-th layer of soil; M—Calculated value of bending moment;
V. ——Calculated value of shear force;
Calculated value of support force at the third layer;
-Design value of axial force;
Design value of bending moment;
-Design value of shear force;
T. —Design value of anchor rod or internal support support force. Engineering Construction Standard Full-text Information System
. Engineering Construction Standard Full-text Information System
2.2.3 Geometric Parameters
%——Center distance of piles;
h——Excavation depth of foundation pit;
h—Design value of embedded depth of supporting structure;
d——Design diameter of pile body;
b-—Thickness of wall body;
-Cross-sectional area of ​​pile (wall) body.
Calculation coefficient
Importance coefficient of side wall of building foundation pit.
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3 Basic Provisions
3.1 Design Principles
The foundation pit support structure shall be designed using the limit state design expression expressed by the partial factor.
3.1.2 The limit state of the foundation pit support structure can be divided into the following two categories: 1. Bearing capacity limit state: corresponding to the support structure reaching the maximum bearing capacity or the soil instability, excessive deformation leading to damage to the support structure or the surrounding environment of the foundation pit; 2. Normal use limit state: corresponding to the deformation of the support structure has hindered the construction of the underground structure or affected the normal use function of the surrounding environment of the foundation pit. 3.1.3
The design of the foundation pit support structure shall select the corresponding side wall safety level and importance factor according to Table 3.1.3.
Safety level and importance factor of foundation pit side wallSafety level
Consequences of being encircled
The damage of supporting structure, instability of soil or excessive deformation has a serious impact on the surrounding environment of foundation pit and underground structure construction
The damage of supporting structure, instability of soil or excessive deformation has a general impact on underground structure construction
The damage of supporting structure, instability of soil or excessive deformation has no serious impact on the surrounding environment of foundation pit and underground structure construction
Note: The safety level of the side wall of construction foundation pit with special requirements can be determined separately according to specific circumstances. Table 3.1.3
3.1.4 The design of the supporting structure shall take into account the influence of the horizontal deformation of the structure and the change of groundwater on the horizontal and vertical deformation of the surrounding environment. For the side walls of the second-level building foundation pit with a safety level of one and limited requirements for the deformation of the surrounding environment, the horizontal deformation of the supporting structure shall be determined according to the importance of the surrounding environment, the ability to adapt to deformation and the nature of the soil. Engineering Construction Standard Full Text Information System
bzsosO, cm1 Resistance and material properties
Engineering Construction Standard Full-text Information System
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-Standard value of soil cohesion;
——Standard value of soil internal friction angle;
-Porosity ratio of soil;
k——Permeability coefficient of soil;
femkfem
fykfpyk
fpy,
-Natural water content of soil,
Gravity density of soil (referred to as soil weight); Average weight of water-concrete wall||t t||Standard value and design value of axial compressive strength of cement soil at excavation age; Proportional coefficient of horizontal resistance coefficient of foundation soil; Standard value and design value of axial compressive strength of concrete; Standard value and design value of bending compressive strength of concrete; Standard value of tensile strength of ordinary steel bars and prestressed steel bars; Design value of tensile and compressive strength of ordinary steel bars; Design value of tensile and compressive strength of prestressed steel bars: Standard value of horizontal resistance at 3 points below the excavation surface of foundation pit; Passive earth pressure coefficient of the i-th layer of soil;
Support stiffness coefficient (spring) coefficient of the support point; Spring coefficient of soil below the excavation surface of foundation pit; Design value of axial tensile bearing capacity of anchor rod.
2.2.2 Action and effect of action
Standard value of horizontal load at point i:
Ka——Active earth pressure coefficient of the i-th layer of soil; M—Calculated value of bending moment;
V. ——Calculated value of shear force;
Calculated value of support force at the third layer;
-Design value of axial force;
Design value of bending moment;
-Design value of shear force;
T. —Design value of anchor rod or internal support support force. Engineering Construction Standard Full-text Information System
. Engineering Construction Standard Full-text Information System
2.2.3 Geometric Parameters
%——Center distance of piles;
h——Excavation depth of foundation pit;
h—Design value of embedded depth of supporting structure;
d——Design diameter of pile body;
b-—Thickness of wall body;
-Cross-sectional area of ​​pile (wall) body.
Calculation coefficient
Importance coefficient of side wall of building foundation pit.
Engineering Construction Standard Full Text Information System
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Engineering Construction Standard Full Text Information System
3 Basic Provisions
3.1 Design Principles
The foundation pit support structure shall be designed using the limit state design expression expressed by the partial factor.
3.1.2 The limit state of the foundation pit support structure can be divided into the following two categories: 1. Bearing capacity limit state: corresponding to the support structure reaching the maximum bearing capacity or the soil instability, excessive deformation leading to damage to the support structure or the surrounding environment of the foundation pit; 2. Normal use limit state: corresponding to the deformation of the support structure has hindered the construction of the underground structure or affected the normal use function of the surrounding environment of the foundation pit. 3.1.3
The design of the foundation pit support structure shall select the corresponding side wall safety level and importance factor according to Table 3.1.3.
Safety level and importance factor of foundation pit side wallSafety level
Consequences of being encircled
The damage of supporting structure, instability of soil or excessive deformation has a serious impact on the surrounding environment of foundation pit and underground structure construction
The damage of supporting structure, instability of soil or excessive deformation has a general impact on underground structure construction
The damage of supporting structure, instability of soil or excessive deformation has no serious impact on the surrounding environment of foundation pit and underground structure construction
Note: The safety level of the side wall of construction foundation pit with special requirements can be determined separately according to specific circumstances. Table 3.1.3
3.1.4 The design of the supporting structure shall take into account the influence of the horizontal deformation of the structure and the change of groundwater on the horizontal and vertical deformation of the surrounding environment. For the side walls of the second-level building foundation pit with a safety level of one and limited requirements for the deformation of the surrounding environment, the horizontal deformation of the supporting structure shall be determined according to the importance of the surrounding environment, the ability to adapt to deformation and the nature of the soil. Engineering Construction Standard Full Text Information System
bzsosO, cm1 Resistance and material properties
Engineering Construction Standard Full-text Information System
bzSoO, CO Ma Engineering Construction Standard Full-text Information System
-Standard value of soil cohesion;
——Standard value of soil internal friction angle;
-Porosity ratio of soil;
k——Permeability coefficient of soil;
femkfem
fykfpyk
fpy,
-Natural water content of soil,
Gravity density of soil (referred to as soil weight); Average weight of water-concrete wall||t t||Standard value and design value of axial compressive strength of cement soil at excavation age; Proportional coefficient of horizontal resistance coefficient of foundation soil; Standard value and design value of axial compressive strength of concrete; Standard value and design value of bending compressive strength of concrete; Standard value of tensile strength of ordinary steel bars and prestressed steel bars; Design value of tensile and compressive strength of ordinary steel bars; Design value of tensile and compressive strength of prestressed steel bars: Standard value of horizontal resistance at 3 points below the excavation surface of foundation pit; Passive earth pressure coefficient of the i-th layer of soil;
Support stiffness coefficient (spring) coefficient of the support point; Spring coefficient of soil below the excavation surface of foundation pit; Design value of axial tensile bearing capacity of anchor rod.
2.2.2 Action and effect of action
Standard value of horizontal load at point i:
Ka——Active earth pressure coefficient of the i-th layer of soil; M—Calculated value of bending moment;
V. ——Calculated value of shear force;
Calculated value of support force at the third layer;
-Design value of axial force;
Design value of bending moment;
-Design value of shear force;
T. —Design value of anchor rod or internal support support force. Engineering Construction Standard Full-text Information System
. Engineering Construction Standard Full-text Information System
2.2.3 Geometric Parameters
%——Center distance of piles;
h——Excavation depth of foundation pit;
h—Design value of embedded depth of supporting structure;
d——Design diameter of pile body;
b-—Thickness of wall body;
-Cross-sectional area of ​​pile (wall) body.
Calculation coefficient
Importance coefficient of side wall of building foundation pit.
Engineering Construction Standard Full Text Information System
.5
Engineering Construction Standard Full Text Information System
3 Basic Provisions
3.1 Design Principles
The foundation pit support structure shall be designed using the limit state design expression expressed by the partial factor.
3.1.2 The limit state of the foundation pit support structure can be divided into the following two categories: 1. Bearing capacity limit state: corresponding to the support structure reaching the maximum bearing capacity or the soil instability, excessive deformation leading to damage to the support structure or the surrounding environment of the foundation pit; 2. Normal use limit state: corresponding to the deformation of the support structure has hindered the construction of the underground structure or affected the normal use function of the surrounding environment of the foundation pit. 3.1.3
The design of the foundation pit support structure shall select the corresponding side wall safety level and importance factor according to Table 3.1.3.
Safety level and importance factor of foundation pit side wallSafety level
Consequences of being encircled
The damage of supporting structure, instability of soil or excessive deformation has a serious impact on the surrounding environment of foundation pit and underground structure construction
The damage of supporting structure, instability of soil or excessive deformation has a general impact on underground structure construction
The damage of supporting structure, instability of soil or excessive deformation has no serious impact on the surrounding environment of foundation pit and underground structure construction
Note: The safety level of the side wall of construction foundation pit with special requirements can be determined separately according to specific circumstances. Table 3.1.3
3.1.4 The design of the supporting structure shall take into account the influence of the horizontal deformation of the structure and the change of groundwater on the horizontal and vertical deformation of the surrounding environment. For the side walls of the second-level building foundation pit with a safety level of one and limited requirements for the deformation of the surrounding environment, the horizontal deformation of the supporting structure shall be determined according to the importance of the surrounding environment, the ability to adapt to deformation and the nature of the soil. Engineering Construction Standard Full Text Information System
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