Detail of JGJ 120-2012

Introduction of JGJ 120-2012

1 General Provisions 1.0.1 This Regulation was develped for the purpose of safety and usability, environmental protection, advanced technology, economy and reasonablity and quality guarantee in the design and construction of building excavations. 1.0.2 This Regulation is applicable to the investigation, design, construction and detection of temporary construction excavations support as well as the excavations excavation and monitor under general geological conditions. This Regulation shall be applied in combination with local engineering experience as for rock excavations and such special soil as collapsible soil, permafrost, expansive soil and salty soil. 1.0.3 The excavations support design, construction and excavations excavation shall take such following factors into consideration as geological conditions, surroundings around excavations requirements, main part underground structure requirements, construction seasons change and support structure service life in accordance with local conditions for reasonable type selection, optimal design, careful construction and strict monitor and control. 1.0.4 Excavations supporting engineering shall comply with those specified in current relevant standards of the nation except the requirements of this Regulation. 2 Terms and Symbols 2.1 Terms 2.1.1 Excavations It refers to the space to be excavated downward from the ground for the construction of underground part of buildings (structures). 2.1.2 Surroundings around excavations The general term for the surrounding buildings (structures), underground pipelines, roads, rock-soil mass and groundwater body in mutual influence with excavation. 2.1.3 Retaining and protection for excavations Measures taken for temporary retaining, reinforcement, protection and groundwater control adopted for excavation to protect the safety of underground main structure construction and surroundings around excavation. 2.1.4 Retaining and protection structure Retaining or reinforcing the structure of the excavation side wall. 2.1.5 Design workable life It refers to the period (specified in the design) from the excavation start to predetermined depth to fulfillment of excavation use function. 2.1.6 Retaining structure The support structure mainly based on structural member for earth retaining and anchor or support or only mainly based on structural member for earth retaining. 2.1.7 Anchored retaining structure Retaining structure mainly based on structural member for earth retaining and anchor. 2.1.8 Strutted retaining structure Retaining structure based on structural member for earth retaining and bracing. 2.1.9 Cantilever retaining structure The retaining component only mainly based on structural member for earth retaining. 2.1.10 Structural member for earth retaining The retaining component arranged on side wall of excavation implanted into excavation bottom, i.e. support pile and diaphragm wall. 2.1.11 Soldier pile wall Retaining component component or cantilever retaining structure composed by support pile and capping beam arranged along excavation side wall. 2.1.12 Double-row-piles wall The retaining structure composed by rigid frame and capping beam connected by the two front and back rows of support piles and beams arranged along the excavation. 2.1.13 Diaphragm wall It refers to the continous underground wall formed by special machinery groove forming and reinforced concrete pouring with groove segment, which may be referred to as cast-in-place diaphragm wall. 2.1.14 Anchor The tension member with one end composed by bolt body (steel strand, prestressed twisted steel reinforcement, ordinary steel bar or steel pipe), jet-grouted solid, anchor and sleeve connected with support structure member and the other end anchored in the stable rock-soil mass. It may be referred to as anchored cable where the steel strand is adopted for bolt body. 2.1.15 Strut The structural component (arranged in excavation) composed by reinforced concrete or steel member in order to support retaining component. Where steel and concrete are adopted for supporting members, they are respectively referred to as steel strut and concrete strut. 2.1.16 Capping beam Reinforced concrete beam (arranged at the top of retaining component) integrating the structural member for earth retaining.

Contents of JGJ 120-2012

Foreword I 1 General Provisions 2 Terms and Symbols 2.1 Terms 2.2 Symbols 3 Basic Requirements 3.1 Principles of Design 3.2 Investigation of Excavated Site and Surrounding Area 3.3 Choice of Structural Types 3.4 Horizontal Load 4 Retaining Structures 4.1 Structural Analysis 4.2 Stability Analysis 4.3 Design of Soldier Pile Wall 4.4 Construction and Test of Soldier Pile Wall 4.5 Design of Diaphragm Wall 4.6 Construction and Testing of Diaphragm Wall 4.7 Design of Anchor 4.8 Construction and Test of Anchor 4.9 Design of Strut 4.10 Construction and Testing of Strut 4.11 Excavations Supported by Permanent Structure and Top-down Method 4.12 Design of Double-Row-Piles-Wall 5 Soil Nailing Wall 5.1 Stability Analysis 5.2 Bearing Capacity Calculation of Soil Nail 5.3 Structural Details of Soil Nailing Wall 5.4 Construction and Testing of Soil Nailing Wall 6 Gravity Soil-Cement Wall 6.1 Stability Analysis and Bearing Capacity 6.2 Structural Details of Gravity Cement-soil Wall 6.3 Construction and Test of Gravity Cement-Soil Wall 7 Groundwater Control 7.1 General Requirements 7.2 Cut-off Drains 7.3 Dewatering 7.4 Drainage Galleries 7.5 Calculation of Ground Settlement due to Dewatering 8 Excavation and Monitoring 8.1 Excavation 8.2 Monitoring Appendix A Kernel of Anchor Pull out Test Appendix B Flexural Bearing Capacity Calculation of R.C.Pile Appendix C Seepage Stability Analysis Appendix D Kernel of Soil Nail Pull out Test Appendix E Simplified Calculation for Water Discharge in Excavation Pit Explanation of Wording in this Specification List of Quoted Standards