Types of Tunnels Used in Transportation-Applications and Construction Procedure

Tunnels have played an important role in human civilization, facilitating transportation, infrastructure development, and various other applications. They come in different forms, each constructed to specific needs and using distinct methods.

Let's discuss the main types of tunnels:

 

Cut-and-Cover Tunnels:

 

Overview: Cut-and-cover tunnels involve digging a trench and covering it with a roof.

 

Applications: Primarily used for underground structures like subways, parking garages, and utility passages.

 

Construction Process: Excavation of the ground, construction of walls and roof, followed by backfilling of the trench.

 

Bored Tunnels:

 

Overview: Bored tunnels are created by tunnel boring machines (TBMs) digging through solid rock or hard materials.

 

Applications: Commonly utilized for transportation routes such as roads, railways, and subways.

 

Variations: Can be single or double-track, and typically deeper than cut-and-cover tunnels.

 

Immersed Tunnels:

 

Overview: Immersed tunnels involve prefabricating tunnel segments on land, floating them to the final location, and submerging them.

 

Applications: Ideal for constructing tunnels under rivers, bays, or other water bodies.

 

Construction Process: Prefabrication of segments, floating them to the site, lowering them onto the seabed, and joining them together.

 

Shield Tunnels:

 

Overview: Shield tunnels utilize shield machines to bore through soft soil or sand.

 

Applications: Suitable for building tunnels in areas where traditional boring machines face challenges.

 

Construction Process: Hydraulic jacks push against tunnel walls, supported by precast concrete segments placed behind the machine.

 

Cavern Tunnels:

 

Overview: Cavern tunnels are excavated chambers underground, either naturally occurring or artificially constructed.

 

Applications: Used for storage facilities, underground power plants, or specialized industrial purposes.

 

Construction Process: Excavation of large chambers in hard rock or softer materials like salt domes or limestone caves.

 

Service Tunnels:

 

Overview: Service tunnels are utility passages carrying water, sewage, or electrical cables.

 

Applications: Vital for maintaining and repairing infrastructure without disrupting regular traffic flow.

 

Construction Process: Typically dug by hand using shovels and other hand tools, designed to accommodate utility needs.

 

 Frequently Asked Questions:

 

What is the primary purpose of cut-and-cover tunnels?

   Cut-and-cover tunnels are primarily used for constructing underground structures such as subways and parking garages.

 

How are bored tunnels constructed, and what materials are they suitable for?

   Bored tunnels are created using tunnel boring machines (TBMs) and are suitable for digging through solid rock or hard materials like clay or shale.

 

What distinguishes immersed tunnels from other types?

   Immersed tunnels involve prefabricated segments floated to the site and submerged, making them ideal for underwater passages.

 

When are shield tunnels preferred over other tunneling methods?

   Shield tunnels are preferred in areas with soft soil or sand, where traditional boring machines may face challenges.

 

What are some common applications of cavern tunnels?

   Cavern tunnels are often used for storage facilities, underground power plants, or specialized industrial purposes.

 

How are service tunnels constructed, and what utilities do they typically accommodate?

   Service tunnels are usually dug by hand and accommodate utilities such as water pipes, sewage lines, and electrical cables.

 

What are the advantages of using tunnel boring machines (TBMs) in tunnel construction?

   TBMs offer faster excavation rates, reduced disturbance to surface structures, and enhanced safety for workers compared to traditional drilling methods.

 

Are there any environmental considerations associated with tunnel construction?

   Yes, tunnel construction can impact local ecosystems, groundwater, and air quality, requiring careful planning and mitigation measures.

 

How do engineers determine the most suitable type of tunnel for a particular project?

   Engineers consider factors such as geological conditions, project budget, environmental impact, and intended use when selecting the appropriate tunneling method.

 

What role do ventilation systems play in tunnel design and construction?

    Ventilation systems are essential for maintaining air quality, controlling humidity, and ensuring the safety of occupants within the tunnel environment.