1 General
1.0.1 This specification has been developed to standardise and guide the design of immersed tunnels for highways.
1.0.2 This specification applies to new road underwater tunnels constructed by the immersed tube method.
1.0.3 The design of immersed tube tunnels shall follow the basic principles of safety, applicability, durability, economy and greenness.
Article description
Immersed tube tunnels should ensure structural and operational safety during construction and use, meet the basic functions of the road, provide a relatively comfortable driving environment, ensure durability during the design life, save construction costs during construction and maintenance costs during use, and contribute to ecological and environmental protection and energy conservation to achieve optimum life-cycle performance.
1.0.4 The design of immersed tube tunnels should be integrated with the superstructure, traffic engineering and ancillary facilities.
Notes
The design of immersed tube tunnels is based on a wide range of disciplines. In the case of civil engineering, consideration should be given to the structure of the immersed tube section and the tunnel structure of the articulated section, the foundation, foundations and backfilling, the road surface and drainage system, the tube section ?± installation facilities, the ancillary structures, etc.; in the case of traffic engineering and ancillary facilities, consideration should be given to traffic safety, ventilation, lighting, water supply and fire fighting, power supply and distribution, etc. It is necessary to comprehensively consider the mutual influence between the various professions and deal with the relationship between the systems in an integrated manner.
1.0.5 The design of immersed tube tunnels should implement the relevant national technical and economic policies and adopt new technologies, materials, equipment and techniques in a positive and prudent manner.
1.0.6 In addition to the provisions of this Code, the design of immersed tube tunnels shall conform to the provisions of the relevant national and industry standards in force.
2 Terminology and symbols
2.1 Terminology
3 Basic provisions
3.0.1 Immersed tube tunnel structures and facilities shall be capable of withstanding the various actions specified during construction and use and shall meet the specified service and durability requirements.
3.0.2 The design service life of immersed tube tunnel structures shall not be less than that specified in Table 3.0.2.
4 Surveys & Surveying
4.1 General provisions
4.1.1 Immersed tube tunnels shall reflect the construction conditions of the project area in a comprehensive manner, using surveys and surveys in accordance with the tasks, aims and requirements of the different phases of the work and taking into account the characteristics of the project.
Article description
The feasibility study phase, with the aim of understanding the full scope of the project, is based on the collection and analysis of existing information, site surveys, supplemented by the necessary site mapping, and the need to give reliable conclusions on the constraining factors and to provide basic information for the selection of the project site, route and programme selection. During the preliminary design stage, a preliminary survey was carried out along the alignment of the tunnel and the necessary mapping and survey work was carried out to identify the controlling conditions for the tunnel design and to provide basic information for the design of the immersed tube tunnel. During the construction design phase, a comprehensive survey method based on drilling verification and testing is used to provide detailed and highly accurate basic information for the construction design. All phases need to be interlinked and the results of the first phase are fully utilised in the second phase.
4.1.2 The main contents of the survey and investigation and the means used are in accordance with the provisions of Table 4.1.2.
5 Materials
5.0.1 Engineering materials for immersed tube tunnels shall be selected according to the type of structure, force conditions, construction techniques, use requirements and the environment in which they are located, and shall meet reliability and economy requirements.
5.0.2 The concrete shall comply with the following provisions:
l The choice of raw materials and the proportion of concrete, strength grade, frost resistance, impermeability grade shall meet the requirements of durability design and waterproof design.
2 The strength grade of concrete for the main structure shall comply with the provisions of Table 5.0.2.
6 Overall design
6.1 - General provisions
6.1.1 The overall design shall include the tunnel location, horizontal and vertical alignment, cross-sectional layout, immersed tube section layout, disaster prevention and rescue, construction planning, etc.
6.1.2 The overall design shall be based on the following principles;
1 conform to the road network, waterway, shoreline and other planning in the area affected by the project 2 meet the prefabrication of pipe sections and floating installation and other process requirements.
3 meet the operational function requirements of safe and comfortable traffic, convenient and economic operation and maintenance, and efficient disaster prevention and rescue.
6.2 Tunnel location
6.2.1 The location of the immersed tube tunnel should be chosen in a stable river, with a gentle river bed. Hydrological conditions window period should meet the requirements of the pipe section floating, immersed in the construction operations.
6.2.2 The location of the immersed tube tunnel should avoid crossing areas with extremely complex geological or environmental conditions, as well as environmentally sensitive buildings (structures); if this cannot be avoided, special demonstration should be carried out and effective countermeasures taken.
7 Pipe section structure
7.1 General provisions
7.1.1 The structural design of pipe joints shall not only meet the functional and structural safety and durability requirements, but also meet the construction and operational maintenance requirements.
7.1.2 The structural design of pipe joints shall include the cross-sectional dimensions of the pipe joints, the type of structure and longitudinal structure, the type of joints, the load-bearing capacity and structural requirements of the main structure and joints, waterproofing measures, etc.
Article description
The structural design of pipe joints is a dynamic and iterative process (Figure 7-1). In the specific design process, the pipe joint structure design process needs to be adjusted or simplified according to the actual situation.
8 Trench, foundation and base, backfill
8.1 General provisions
8.1.1 The design of the foundation trench shall be based on the geological and hydrological conditions of the area where the immersed tube tunnel is located, taking into account the requirements for the level and longitudinal plane of the tunnel, the cross-section of the tube section, the floating and installation of the tube section, the technology and equipment for the construction of the foundation, etc.
8.1.2 The foundations and foundations should meet the requirements for bearing capacity o deformation and stability during the construction and use phases.
8.1.3 The backfill shall meet the requirements for floatation, lateral movement and protection of the pipe section structure and shall be resistant to scouring.
Article description
In addition to meeting the requirements of the pipe section for anti-floating and anti-lateral slip, the backfill shall also have the function of protecting the pipe section under accidental conditions such as anchoring, anchor towing, ship striking, etc. At the same time, the backfill and its composition shall have the ability to resist scouring under the action of water currents, etc.
9 Articulation section
9.0.1 The design of the articulated section shall be based on the tunnel structure and construction techniques, the docking requirements of the pipe section, and the design of the articulated section in conjunction with the shore protection works to meet the functional, force, impermeability and flood protection requirements.
Article description
The tunnel structure of the articulated section is generally constructed in-situ in the shore pit, with temporary measures and structures such as cover cofferdams and pit supports, taking into account the requirements related to the docking of adjacent pipe sections, such as the removal of partial shoring before docking and restoration after docking, and sufficient axial thrust resistance of the concealed section.
9.0.2 The comprehensive design of the tunnel structure and the adjacent pipe section shall be carried out in an integrated manner, taking into account the foundation, overlying loads, etc.
10 Analytical calculations
10.1 General provisions
10.1.1 The structure and foundations of immersed tube tunnels shall be subjected to endurance, transient, accidental and seismic limit state calculations to meet strength, stiffness and stability requirements.
11 Design for durability
11.0.1 The durability design of immersed tube tunnel structures shall be based on the design life of the structural elements, the type of environment in which they are located and the level of action, and shall determine the material durability indicators, structural measures to mitigate the effects of the environment, and additional measures to prevent corrosion.
12 Pipe joints and sprite installation facilities
12.0.1 The design of the end walls, ballast water devices, bollards, lifting points, measuring towers, guides, pulling devices, manholes, etc. shall be carried out in accordance with the principles of safety, reliability, ease of dismantling, economy and reasonableness.
13 Pavement and drainage system
13.1 Pavement
13.1.1 The pavement of the immersed tube tunnel shall be designed taking into account the structural conditions of the project, traffic loading, environmental climate, construction conditions and maintenance convenience, to meet the performance requirements of leveling, durability, anti-slip, wear resistance and environmental protection.
13.1.2 The pavement of the immersed tube tunnel should be a composite pavement structure with two layers of asphalt pavement, with a total thickness of 80-100mm, and should be provided with a waterproof bonding layer.
14 Accessory structures
14.1 General provisions
14.1.1 Accessory structures shall be planned and coordinated with the main structure, traffic engineering and ancillary facilities to facilitate construction and maintenance at a later stage.
14.1.2 Gutters and cable ditches, decorative layers, cavity light reduction structures shall be set up according to their function and shall comply with the current Code of Practice for the Design of Road Underwater Tunnels (JTG/T3371).
14.2 Escape routes
14.2.1 Escape routes shall comply with the following provisions:1 Escape routes shall be set up in the service corridor.
2 escape opening spacing should be comprehensive examination of the total tunnel length, the length of the pipe section, traffic volume and composition, ventilation facilities, fire-fighting facilities and other factors to determine, appropriate for 100 two 150m,
3 The net width of the escape route and escape white should not be less than 1.2m and the net height should not be less than 2.1m.
15 Traffic engineering and ancillary facilities
15.1 - General provisions
15.1.1 Traffic engineering and ancillary facilities shall be coordinated with the main structure of the immersed tube tunnel and the connection works at both ends of the tunnel, with comprehensive traffic safety facilities, ventilation facilities, lighting facilities, water supply and fire fighting facilities, power supply and distribution facilities, central control management system and monitoring facilities.
16 Structural monitoring
16.0.1 Structural monitoring of the immersed tube tunnel shall be carried out in two phases, during the construction and operation periods.
17 Risk Analysis
17.0.1 Risk analysis shall be carried out during the design phase of the immersed tube tunnel to optimise risk control measures and to achieve effective dynamic control of risk.
Appendix A Calculation of double steel plate - concrete combination structures
Explanation of terms used in this specification
1 General
2 Terminology and symbols
3 Basic provisions
4 Surveys & Surveying
5 Materials
6 Overall design
7 Pipe section structure
8 Trench, foundation and base, backfill
9 Articulation section
10 Analytical calculations
11 Design for durability
12 Pipe joints and sprite installation facilities
13 Pavement and drainage system
14 Accessory structures
15 Traffic engineering and ancillary facilities
16 Structural monitoring
17 Risk Analysis
Appendix A Calculation of double steel plate - concrete combination structures
Explanation of terms used in this specification
