1 General Provisions
1.0.1 With a view to ensuring the quality and safety of building foundation pit engineering and being convenient for the knowledge acquisition and application by the design, construction, supervision and other departments, this code is formulated according to principles of technical advancement, economy and rationality as well as safety applicability.
1.0.2 This code is applicable to foundation pit engineering of building and structure equipped with basement or underground structure.
1.0.3 This code is formulated in accordance with the basic principles specified in the national standard "Unified Standards for the Design of Structures" (GBJ 68-84). Symbols, measurement units and basic terms meet the requirements of "Design of Structures - General Symbols Units of Measurement and Basic Terms" (GBJ 83-85).
1.0.4 The design, construction, monitoring and acceptance of building foundation pit engineering shall not only meet the requirements of this code, but also complies with those of relevant codes such as "Building Constructions - Specifications for Loads of Architectural Structures", "Foundation Design Code", "Code for Investigation of Geotechnical Engineering", "Code for Design of Concrete Structures", "Code for Design of Steel Structures" and "Code for Collapsible Loess Foundation".
1.0.5 Basic function of foundation pit engineering shall meet:
1) Space requirements and safety of underground work construction;
2) Safety of subgrade and pile foundation for the main work;
3) Environmental safety, including adjacent metro, tunnel, pipeline, house building, underground utility and etc.
1.0.6 The foundation pit support structure, where regarded as a part of permanent work, shall meet the design requirements of permanent work.
2 Terms and Symbols
2.1 Terms
2.1.1 Foundation pit engineering: during construction of underground part of building or structure, foundation pit excavation, construction dewatering and foundation pit enclosure shall be carried out; meanwhile, monitoring and maintenance shall be carried out for buildings, structures, roads and underground pipelines around the foundation pit so as to ensure normal safety construction. This comprehensive engineering is referred to as foundation pit engineering.
2.1.2 Lateral pressure: the lateral pressure acted on support structure, including the soil pressure, water pressure, ground surcharge load as well as the lateral load caused by loads of construction vehicle, machinery, adjacent structure and etc.
2.1.3 Cement-soil gravity type retaining wall: the continuous wall-shaped or grid-shaped cement-soil soil-retaining and waterstop wall formed through mixing of cement paste and soil with deep stirring method.
2.1.4 Support structure: the structure used for bracing anchor and enveloping foundation pit periphery so as to remain the soil stability, including envelope (soil-retaining pile, wall and waterstop wall), brace-anchor structure (inner brace, anchor bolt and anchor-pulling structure) and etc.
2.1.5 Piling-wall envelope: the support structure composed of distributed pile structure or continuous wall structure (including underground continuous wall), brace inside pit or anchor-pulling structure outside pit.
2.1.6 Cantilever envelope: the piling-wall envelope with top end free while lower end partly embedded in the soil to depth.
2.1.7 Brace inside pit: the brace acted on the foundation pit, which is generally composed of brace, waist beam, vertical column and etc. so as to form an inner-bracing system.
2.1.8 Plane brace system: the plane bar-system structure arranged within the foundation pit above the excavated surface to balance partial lateral pressure acted on envelopes at two opposite sides or adjacent side of foundation pit.
2.1.9 Vertical diagonal brace system: the diagonal bar-system structure arranged along the envelope periphery within the foundation pit to transfer partial lateral pressure on foundation pit envelop to the subgrade below the excavated surface.
2.1.10 Anchor-pulling type: the anchor bolt made outside the foundation pit and fixed on the envelope with waist beam to form an anchor-pulling system.
2.1.11 Waist beam: the horizontal beam arranged between the end of brace or anchor bolt and the envelope and penetrating throughout the envelope periphery.
2.1.12 Pile-top connecting beam: the horizontal beam arranged on top of row piles which is connected with piles, penetrating throughout the periphery of row piles to make them as a whole.
Foreword I
1 General Provisions
2 Terms and Symbols
2.1 Terms
2.2 Symbols
3 Basic Provisions
4 Geotechnical Engineering Investigation
4.1 General Requirements
4.2 Exploration and Testing
4.3 Investigation Report
5 Soil Pressure
5.1 General Requirements
5.2 Static Soil Pressure
5.3 Active and Passive Soil Pressure
5.4 Adjustment of Soil Pressure Coefficients
5.5 Effect of Underground Water on Soil Pressure
5.6 Adjustment of Soil Strength Index
5.7 Calculation of Soil Pressure under Other Conditions
6 Foundation Pit Stability
6.1 General Requirements
6.2 Checking for the Stable Embedded Depth of the Support Structure
6.3 Checking for Anti-upheaval Stability at Foundation Pit Bottom
6.4 Checking for Anti-seepage Stability at Foundation Pit Bottom
6.5 Calculation for the Overall Stability of Foundation Pit
7 Step-slope
7.1 General Requirements
7.2 Design
7.3 Slope Surface Protection
8 Soil Nailing Support and Shotcrete-bolt Support Structure
8.1 General Requirements
8.2 Soil Nailing Support
8.3 Shotcrete-bolt Support Structure
9 Cement-soil Gravity Type Retaining Structure
9.1 General Requirements
9.2 Design
9.3 Construction
10 Piling-wall Envelope
10.1 General Requirements
10.2 Calculation
10.3 Design
10.4 Construction
11 Inner Brace of Envelope
11.1 General Requirements
11.2 Type Selection and Layout for Inner Brace System
11.3 Load and Internal Force
11.4 Bearing Capacity Calculation and Deformation Requirements for Brace Member Section
11.5 Constructional Requirements
11.6 Essentials in Construction
12 Anchor Bolt
12.1 General Requirements
12.2 Design
12.3 Construction
13 Underground Water Control
13.1 General Requirements
13.2 Dewatering
13.3 Foundation Pit Waterstop
14 Foundation Pit Soil Reinforcement
14.1 General Requirements
14.2 Reinforcement inside of Pit
14.3 Reinforcement outside of Pit
14.4 Technical Essentials for Soil Reinforcement of Foundation Pit
15 Foundation Pit Excavation
15.1 General Requirements
15.2 Foundation Pit Excavation
15.3 Accident Treatment during Foundation Pit Excavation
16 Top-down Method for Foundation Pit Engineering
16.1 General Requirements
16.2 Construction
16.3 Design
17 Foundation Pit Deformation Control
17.1 General Requirements
17.2 Design Measures
17.3 Construction Measures
17.4 Emergency Measures
18 Foundation Pit Engineering in Rock
18.1 General Requirements
18.2 Design
18.3 Construction
19 On-site Monitoring of Foundation Pit Engineering
19.1 General Requirements
19.2 Monitoring Contents
19.3 Monitoring Methods
Appendixes
Appendix A Type Selection of Foundation Pit Support Structure
Appendix B Coefficients of Coulomb Active and Passive Soil Pressure
Appendix C Proportionality Coefficient Value Kh of Lateral Soil Subgrade Bed
Appendix D Calculation of Soil Pressure under Additional Load
Appendix E Essentials in Calculation of Cantilever Envelope
Appendix F Essentials in Calculation of Anchor-bracing Envelope with Equivalent Beam Method and Static Balance Method
Appendix G Slope Type
Appendix H Construction Technique of Shotcrete-bolt Support Structure
Appendix J Local Reinforcement Design of Soil Nailing Support
Appendix K Calculation of Shotcrete-bolt Support Structure
Appendix L Essentials in Calculation of Bar-system Finite Element Method and Spatial Plate-shell Element Method on Lateral Subgrade
Appendix M Essentials in Anchor Bolt Test
Appendix N Selection of On-site Monitoring Item
Appendix P Treatment Measures for Abnormal Conditions during Foundation Pit Construction
Appendix Q Explanation of Wording in this Standard
Additional Explanation
