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With the continued development of urban rail transit, underground utility tunnels, and highway tunnel projects, tunnel boring machine (TBM) construction has become widely used because of its high efficiency and relatively low impact on surface traffic. During long-distance underground excavation, the working environment is relatively enclosed, with workers, equipment, and construction activities concentrated in a limited space. This can result in insufficient air circulation, heat accumulation, dust, and increased concentrations of harmful gases. Therefore, a well-designed TBM construction ventilation system solution is an important part of maintaining a safe working environment and ensuring continuous tunnel construction.
BM tunnels are generally long and have relatively limited cross-sectional areas. As excavation progresses, the distance between the tunnel entrance and te working face increases, making it more difficult to deliver fresh air to the remote working area.
Mechanical ventilation can continuously supply fresh air to the excavation area while removing hot air, dust, and contaminated air. This helps improve the internal tunnel environment and provides better working conditions for construction personnel.
Construction Equipment Generates Heat and Pollutants
TBMs, transport equipment, electrical systems, and other construction machinery generate heat during operation. Certain construction activities may also produce dust and other pollutants. As the number of workers and machines increases, maintaining good air quality becomes more challenging.
Therefore, a TBM construction ventilation system should not only meet basic air exchange requirements but also adjust ventilation capacity according to different construction stages and equipment loads.
Main Components of a TBM Construction Ventilation System
The main purpose of the air supply system is to deliver fresh outdoor air to the TBM working area. It generally consists of fans, flexible ventilation ducts, duct connectors, and related auxiliary equipment.
As the TBM advances, the ventilation duct must be extended continuously. Therefore, the weight, flexibility, connection method, and durability of the ventilation duct can directly affect construction efficiency.
Exhaust System
For construction areas where dust, heat, or other pollutants are generated, an exhaust system can be installed according to actual site requirements. It removes contaminated air from the tunnel and helps maintain a cleaner working environment.
The supply and exhaust systems should be properly coordinated to prevent fresh air from being exhausted before reaching the main working area, thereby improving overall ventilation efficiency.
Fans and Control Equipment
Fans are the primary power equipment in a TBM construction ventilation system. Different types and specifications of ventilation fans can be selected according to tunnel length, cross-sectional dimensions, airflow, and pressure requirements.
For long-distance TBM construction, variable-frequency control can be used to adjust fan operation according to excavation distance and actual working conditions. This helps meet ventilation requirements while controlling energy consumption.
How to Select a TBM Construction Ventilation Method
Forced air supply ventilation uses fans to deliver fresh air directly to the excavation face through flexible ventilation ducts. It is one of the common ventilation methods used in TBM construction.
This method can deliver fresh air to working areas located far from the tunnel entrance and is suitable for long-distance underground construction. During system design, attention should be paid to duct leakage, pressure loss, and airflow performance at the duct outlet.
Exhaust Ventilation
Exhaust ventilation uses exhaust equipment to remove contaminated air from the construction area, while fresh air enters the tunnel through other passages.
This method can be considered for construction areas where pollutants are generated in concentrated locations, depending on the actual tunnel layout and operating conditions.
Combined Ventilation
For long-distance TBM projects with complex construction processes, supply and exhaust ventilation can be combined to create a more effective airflow pattern for different working areas.
A combined system can provide greater flexibility and allow ventilation capacity to be adjusted according to the specific conditions of each construction zone.
| Construction Stage | Main Air Quality Issues | Recommended Ventilation Method | Key Considerations |
|---|---|---|---|
| Initial Excavation | Heat, dust, insufficient air exchange | Forced air supply | Air supply capacity |
| Medium-Distance Excavation | Pressure loss, insufficient air circulation | Long-distance air supply | Duct resistance |
| Long-Distance Excavation | Declining air quality at the far end | Enhanced supply and exhaust | Airflow and pressure |
| High-Temperature Construction | Heat accumulation, worker comfort | Mechanical ventilation + enhanced air supply | Cooling and air exchange |
| Complex Construction Operations | Dust, contaminated air | Combined ventilation | Local exhaust |
Application of PVC Flexible Ventilation Ducts in TBM Construction
During TBM construction, ventilation distances increase continuously as excavation progresses, so ventilation ducts must also be extended. Compared with rigid ventilation ducts, flexible ventilation ducts offer advantages such as lower weight, convenient transportation, quick installation, and flexible layout. These characteristics make them suitable for changing construction environments.
PVC-coated fabric can be used to manufacture flexible ventilation ducts for TBM construction. Different diameters, lengths, and structural configurations can be produced according to project requirements.
Proper selection of ventilation duct materials can reduce installation difficulties and help maintain stable air supply performance throughout the construction process.
When selecting ventilation ducts, attention should be paid to abrasion resistance, tear resistance, airtightness, connection methods, and long-term operating stability. The duct diameter should also be selected according to fan performance and tunnel length to reduce unnecessary pressure loss.
Improving TBM Ventilation Efficiency Through Intelligent Monitoring
Modern TBM construction ventilation systems can be integrated with temperature, humidity, dust, and harmful gas monitoring equipment to monitor tunnel air conditions in real time.
When abnormal conditions are detected, fan operation can be adjusted promptly to improve the working environment.
Adjusting Airflow According to Excavation Distance
As excavation progresses, ventilation system pressure losses increase. Variable-frequency fans and intelligent control systems can adjust fan operating parameters according to actual excavation distance and air quality.
This prevents ventilation equipment from operating continuously at maximum capacity when it is not necessary, helping reduce energy consumption while maintaining suitable airflow.
How to Build an Efficient TBM Construction Ventilation System
A complete TBM construction ventilation system solution should consider tunnel length, TBM type, construction processes, workforce, equipment heat load, and pollutant sources.
By selecting suitable forced air supply, exhaust, or combined ventilation methods and integrating high-performance fans, PVC flexible ventilation ducts, air monitoring equipment, and intelligent control systems, a stable construction ventilation system can be established.
As the excavation distance increases, fan parameters and duct layouts should be adjusted accordingly. Regular inspection and maintenance of ventilation equipment and ducts are also essential.
Through scientific system design, appropriate equipment selection, and continuous maintenance, the underground construction environment can be effectively improved. This provides construction workers with more stable air conditions while supporting the safe and efficient operation of long-distance underground engineering projects.
