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.
