What are the top tunnel ventilation systems for soft ground?

Longitudinal Ventilation System: Key Points Simple and Common: Easiest type of tunnel ventilation, often used in soft ground tunnels. Airflow Like a Straw: Fresh air enters one end, exits the other, pushing out fumes. Fans Give a Boost: Jet fans act like powerful air pumps along the tunnel to keep air flowing. Best for Short Tunnels: Works well for tunnels under 3-6 km with low traffic density. Air Quality Concerns: Pollution levels increase as you travel deeper due to limited fresh air injection. Limited Control: Less control over airflow direction and speed compared to other systems. Noise Concerns: Can be noisy due to powerful fans. Fire Safety: Good for managing smoke direction in case of fire.

Transverse Ventilation System: Air Vents Everywhere: Fresh air constantly enters through ceiling vents, while fumes exit through floor vents, keeping the air clean. Long Tunnels & Busy Traffic: Works best for long tunnels (over 3-6 km) with lots of cars. Clean Air & Quiet Ride: Provides fresh air throughout, reducing noise for a more pleasant journey. More Expensive & Space Hungry: Installing vents takes up space and costs more than simpler systems. Control Knobs for Air: Engineers can adjust airflow at different points in the tunnel. Fire Safety Hero: Quickly removes smoke during fires, improving visibility and safety.

The key points of semi-transverse ventilation in even simpler terms: Mix of Air Vents and Tunnel Flow: Imagine a tunnel with air vents in the ceiling bringing in fresh air, but instead of special vents to suck out fumes, the tunnel itself pushes them out like blowing through a straw. Good for Tunnels Not Too Short, Not Too Long: Works best for tunnels of medium length with a moderate amount of traffic. Cleaner Air, More Affordable: Keeps the air fresher than a simple system, but costs less to set up than full air vents. Not Perfect Control: It's harder to control exactly where the fresh air goes and how fast fumes leave. Not the Most Powerful: Might not be as good at removing fumes as a full air vent system.

Piston Effect Ventilation: Trains as Air Pumps: Trains act like giant plungers, pushing air ahead and sucking air behind them as they move. Busy Train Tunnels: Works best in tunnels with frequent and fast train service (metros, railways). Saves Money and Space: No need for expensive fans and vents, using trains themselves to move air. Uneven Airflow: Air might not be spread evenly throughout the tunnel, creating gusts or uneven air quality. Sensitive to Train Schedule: Relies on train movement, so air flow gets disrupted if trains slow down or stop frequently.

CFD is like a computer program that helps engineers design tunnel ventilation systems by showing how air flows, heat moves, and pollutants spread inside tunnels. It's like a virtual test lab where engineers can try different ideas to make sure the tunnels are safe and work properly.

variable speed drives can be used in ventilation systems as they provide flexibility to adjust fan speeds based on real-time conditions which is advantageous in soft ground tunnels with variable ventilation requirements.

1) Jet fans: These are commonly used for longitudinal ventilation in tunnels.They provide efficient air flow and can be installed along the length of the tunnel to ensure proper ventilation. 2) Axial flow fans: These fans are suitable for both longitudinal and transverse ventilation.They can be installed at regular intervals along the tunnel to provide adequate air flow and remove pollutants. 3) Transverse ventilation duts: These duts are installed across the tunnel to provide cross ventilation.They help in removing smoke,heat and other pollutants from the tunnel. 4) Smoke extraction system: These systems are designed specifically to remove smoke from the tunnel in the event of a fire. 5) Computational Fluid Dynamics simulations.