ACI (American Concrete Institute) Standards · International Standards
Metro station construction techniques refer to the collective term for a systematic set of construction methods, technical approaches, and quality control procedures employed in urban underground environments for the main structure, retaining structure, ancillary structures, and MEP embedded works of metro stations. It encompasses the entire process from retaining structure construction, excavation, main structure execution, waterproofing, backfilling and restoration, to interior structural finishing—representing a concentrated embodiment of underground engineering construction capability.
Regarding the formulation background: As China's urban rail transit enters a period of large-scale construction, metro stations face typical challenges characterized by "depth, scale, density, and risk": excavation depths commonly reach 20–35 meters, surrounding buildings and structures are densely distributed, underground utilities are complex, and hydrogeological conditions are highly variable. Meanwhile, as Chinese general contractors go global at scale, undertaking metro projects in the Middle East, Southeast Asia, Africa, and South America, there is an urgent need for a construction technique system that aligns with Chinese national standards while remaining compatible with international standards and local codes. As a result, the industry has gradually formed a technique spectrum centered on open-cut, cover-and-cut, and mined methods, continuously iterating through overseas projects.
In terms of applicable scope, this technique system applies to:
It should be noted that the specific method adopted for a given project must be determined through comprehensive comparison and selection based on geological investigation reports, surrounding environment, schedule, and cost. For relevant standard numbers and contract clauses, please refer to official documents.
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The retaining structure is the first line of defense for station excavation safety. Common forms are compared below:
| Retaining Form | Applicable Depth | Applicable Strata | Characteristics |
|---|---|---|---|
| Diaphragm wall | 20–50m | Soft soil, sand, rock | High rigidity, good water cutoff, can serve as permanent wall |
| SMW piles | 10–25m | Soft soil, fill | Low cost, fast schedule, requires H-pile extraction |
| Bored piles + waterproof curtain | 15–40m | Various strata | Flexible, highly adaptable |
| Secant piles | 15–30m | Water-rich soft soil | Reliable water cutoff, no additional curtain needed |
For overseas projects, particular attention should be paid to: Europe commonly uses diaphragm walls + internal bracing systems; Southeast Asian soft soil areas often adopt SMW or secant piles; Middle Eastern rock strata typically use bored piles + anchor cables. Before construction, critical procedures such as guide walls, slurry mix design, and trench verticality control must be completed.
Excavation follows the principles of "layered, partitioned, symmetrical, and time-limited." Core control points include:
Overseas projects often require third-party monitoring and alignment with local alarm threshold standards.
The main structure typically adopts the bottom-up method or top-down method:
| Method | Construction Sequence | Applicable Scenarios | Pros and Cons |
|---|---|---|---|
| Bottom-up | Excavate to bottom → construct from bottom up | Conventional stations | Mature process, quality easily controlled |
| Top-down | Construct roof slab and middle slab from top down | Sensitive surroundings, tight schedule | Shortens schedule, controls deformation, but complex joints |
Key procedures include: blinding and waterproofing layer, rebar tying, formwork installation, concrete pouring and curing, construction joint and movement joint treatment. Waterproofing grade generally requires no lower than Grade 2; overseas projects often reference local waterproofing codes or Eurocodes.
Metro station waterproofing is central to operational safety. Common practices:
Ancillary structures (entrances/exits, ventilation shafts, passages) often use open-cut, mined, or pipe-jacking methods, requiring interface coordination with the main structure.
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| Comparison Dimension | Chinese National Standards (GB Series) | International Standards (ISO/EN) | Local Standards (Examples) |
|---|---|---|---|
| Design philosophy | Centered on bearing capacity and deformation control | Emphasizes performance-based design and whole-life cycle | Often inherits colonial-era or regional codes |
| Excavation monitoring | Graded alarms with clear quantitative indicators | Emphasizes risk assessment and observational design | Alarm values often set by local authorities |
| Waterproofing requirements | Graded protection with detailed joint drawings | Focuses on material performance and system compatibility | Varies widely; requires item-by-item verification |
| Construction acceptance | Itemized and divisional acceptance with complete documentation | Emphasizes ITP and third-party witnessing | Often requires local supervision approval |
Overall, Chinese national standards have advantages in the level of construction technique detail, while international standards are more systematic in performance-based design and risk management. Overseas projects should adopt a fusion strategy of "Chinese techniques as the foundation, international standards as the framework, and local codes as the baseline." For specific standard numbers and clauses, please refer to official documents.
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Scenario 1: Station-supporting works along the Jakarta–Bandung High-Speed Railway
As a flagship Belt and Road project, the Jakarta–Bandung HSR involves station and underground supporting structure construction in Bandung and other locations in Indonesia. The project faced challenges including volcanic ash soft soil and high groundwater levels, adopting a bored pile + waterproof curtain retaining system and optimizing concrete curing processes to suit local climatic conditions. Public reports indicate that the project accumulated experience in localized labor practices and technical standard alignment.
Scenario 2: Station construction along the China–Laos Railway
The China–Laos Railway traverses complex mountainous terrain and tropical rainforests, with some stations involving deep excavations and high slopes. The project adopted a combination of open-cut method and anchor cable support, developing specialized drainage and monitoring plans for rainy-season construction. Public information indicates that the project has demonstrative significance in cross-border standard coordination and material logistics.
Scenario 3: Urban rail transit project in the Middle East
In a Middle Eastern city metro project, Chinese general contractors faced high temperatures, rock strata, and stringent European/American standard requirements, adopting a diaphragm wall + concrete internal bracing system and introducing third-party monitoring. The project developed reusable overseas construction experience in standards benchmarking, material certification, and HSE management.
The above project information is sourced from public reports. For specific technique parameters and contract details, please refer to official documents.
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Q1: Should overseas projects prioritize Chinese standards or international standards?
A: It depends on contract provisions. Typically, the owner-specified standard prevails, with Chinese standards serving as technical support. It is recommended to complete a standards benchmarking checklist during the bidding stage, identifying discrepancies and alternative solutions.
Q2: How to control deformation in station excavations in soft soil strata?
A: The key is "brace before excavating, time-limited bracing, and observational construction." This can be combined with in-pit improvement, dewatering, and servo bracing systems, with monitoring data fed back in real time to guide construction.
Q3: How to choose between top-down and bottom-up methods?
A: Top-down is preferred when surroundings are sensitive, schedule is tight, and deformation requirements are stringent; bottom-up is more economical and quality is easier to control under conventional conditions. A comprehensive comparison of cost, schedule, and risk is required.
Q4: How to select waterproofing materials for overseas projects?
A: Must simultaneously satisfy the design waterproofing grade, local material certification, and climate adaptability. It is recommended to prioritize materials with international certifications (e.g., CE, ASTM) and local supply channels.
Q5: How to address standard conflicts in overseas projects?
A: Establish a "standards matrix" to compare design, construction, and acceptance requirements item by item. For conflicting items, communicate with the owner and supervisor in advance to form written clarifications or variation bases.
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1. Engage in standards benchmarking at the bidding stage: Organize technical, commercial, and legal teams to jointly review the contract standards system, forming a discrepancy list and response plan.
2. Establish a dynamic geological and environmental database: Integrate investigation, monitoring, and meteorological data to support dynamic adjustment of construction plans.
3. Promote observational construction: Deploy automated monitoring and BIM collaborative platforms to achieve deformation early warning and process linkage.
4. Strengthen localized material and labor management: Complete material certification, labor quotas, and training plans in advance to reduce compliance risks.
5. Refine waterproofing and joint techniques: Prepare joint detail drawings and work instructions, implementing first-article acceptance and mock-up guidance.
6. Improve HSE and emergency response plans: Develop specialized plans for high temperature, heavy rain, karst, and other special conditions, with regular drills.
7. Emphasize contract and claims management: Timely preserve evidence for geological changes, standard changes, and schedule delays, asserting rights under FIDIC clauses.
8. Build a technique knowledge base: Transform overseas project experience into enterprise-level technique standards and training materials, forming replicable construction capability.
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The above content is compiled based on public information and general industry practices. For specific standard numbers, project amounts, and contract clauses, please refer to official documents.