Tunnels are artificial underground passages constructed for various purposes like transportation, navigation, water supply, sewer, hydro-power, public utility, canals, etc.
In this article, we mainly discuss the point should consider while selecting the alignment of the tunnel. And also the necessary things such as Tunnel Drainage, Lighting Of Tunnels, Tunnel Ventilation and Lining In Tunnel respectively.
While selecting the alignment of the tunnel following points should be considered :
- The route should as short as possible
- The straight path is preferred
- Easily accessible
- Careful selection of entry and exit location
Factors affecting the tunneling
- Land topography
- Geological selection of the alignment
- Hard rocks
- Creep or tectonic movements
Factor need to consider while doing work of alignment of the tunnel
1. Tunnel Drainage
PRE DRAINAGE: A drainage arrangement before the construction of the tunnel is known as pre-drainage.
DE-WATERING: It is the drainage arrangement that is carried out during the construction time of the tunnel.
PERMANENT DRAINAGE: The methods of permanent drainages are:
- Provision of longitudinal pipelines
- Concrete lining
- Grouting with cement or chemicals
2. Lighting Of Tunnels
The lighting of the tunnel is a very important environmental factor to utilize the full efficiency of manpower or machine involved in work with proper safety.
The minimum requirements for lighting in tunnel are as follows:
- Adequate lighting should be provided at each and every point
- Lighting at the working face should be provided
- Lamps should be fixed at both sides and center
- Hauling equipment should have their own lighting system
- Excavating equipment and other heavy equipment should have their own lighting system
3. Tunnel Ventilation
Ventilation is the process of replacing used air with fresh air. It is done by both artificial and natural methods.
Objectives of ventilation:
- To replace the used air by fresh air
- To remove harmful gases
- Supply adequate amount of oxygen to workers
- Remove the excessive amount of moisture present inside the tunnel.
4. Lining In Tunnel
Tunnel lining is a part of the support design provides inside the construction area of tunnels. Lining can be done by brick, timber, concrete, stone, rock reinforcement, steel, etc.
Objectives of lining in tunnel:
- It withstand the soil pressure
- It gives support to loose soil
- Provides proper shape to the tunnel
- It strengthen the weak portion
- It makes the tunnel free from water penetration
- To ensure streamline flow for water tunnels.
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