What Is Tunel | Types of Tunnels | What Are Tunnels Used for | Classification of Tunnel | How Are Tunnels Built |Advantages of Tunnels | Disadvantages of Tunnels

What Is Tunel?

Tunnels are artificial underwater tunnels that are built without damaging the surface of the earth. The tunnels are underwater passageways used mostly for transport purposes. They may be used to transport freight and travellers, water, sanitation, respectively.

Tunnels are often more efficient than open cuts over a certain depth. Tunnels prevent disruption or interaction with surface life including traffic throughout construction.

Tunnels appear economical than bridges or open cuts for public sector utilities such as water, sewer as well as power.

Also, Read: Definition Spillway | What Is a Spillway | 6 Types of Spillway | Essential Requirements of Spillway | Spillway Design

What Are Tunnels Used for

• Mining of ores.
• Transport like road buses, trains, subways as well as canals.
• Driving water and sanitation.
• Underground chambers, mostly connected with a network of interconnected tunnels as well as shafts, being frequently used in those items as underground hydroelectric power plants, ore processing plants, pumping stations, car parks, oil and water storage, water treatment plants, warehouses.
• Light development.
• The Command Centers.
• Special needs of the military.

How Are Tunnels Built?

• Tunnels were created in kinds of materials ranging from soft mud to heavy rock.
• The process of tunnel design relies on aspects including such as terrain conditions, ground water circumstances, the diameter including the length of the tunnel drive, its size of the tunnel, its material support for tunnel drilling, the final application including a form of the tunnel as well as the necessary risk management.
• The construction of tunnels is a branch of underground construction.

There have been three basic categories of tunnel design widely used:

1. Cut and cover tunnel, built in a shallow trench and afterward sealed.
2. A sealed tunnel, built-in place, without destroying the above ground. These typically have a circle or a horseshoe cross-section. Any principles of the underground mining section applies. New technologies involve Shotcrete used for the new Austrian tunnelling system, by use of a tunnel boring machine (TBM) or even a tunnelling shield. Although tunnels are always built, protected of pit props including shoring, but instead stained or timer supports were placed. Techniques such as barrel vaults are beneficial.
3. Immersed tube tunnel, plunged into such a water body but placed to and placed just beneath its bed.

Also, Read: Spandrel Beam Definition | Properties of Spandrel Beam | Advantages & Disadvantages of Spandrel Beam | Uses of Spandrel Beam | Spandrel Beam Design

How Are Underwater Tunnels Made?

• An underwater tunnel is a tunnel that is partially or entirely built beneath the sea or perhaps an estuary.
• These are also used whenever constructing a bridge or running a ferry link is not feasible, as well as provide support or relaxation for existing bridges or ferry connections.
• Although short tunnels are mostly road tunnels that can be used for motorized, unmotorized, or even both, ventilation problems contribute to the lengthy tunnels.

Types of Tunnels

Tunnels can, on the bases of with there function, be categorized into the following three major classes-

• Traffic Tunnels.
• Hydropower Tunnels.
• Public Utility Tunnels.

1. Traffic Tunnels

Tunnels which are unearthed for the purpose of diverting traffic loads from the ground to subsurface roads for a limited distance to facilitate. Traffic movement at the optimal level, optimum comfort, and at a minimal expense is referred to as traffic tunnels.

Types of traffic tunnels

• Railway tunnels.
• Highway tunnels.
• Pedestrian tunnels.

Traffic tunnels offer a safe and cost-effective solution to direct travel, including between two locations isolated by large barriers such as cliffs, valleys, water sources, or even heavily populated areas of urban cities.

2. Hydropower Tunnels.

While the title indicates, such tunnels are being unearthed from the production of hydropower. These are pushed around rocks bringing underneath gravity the water.

3. Public Utility Tunnels.

Such specially modified tunnels are unearthed for the dumping of urban waste, for the transport of pipes, cables and oil sources, including water, respectively. Nowadays, they have also unearthed for underground parking and processing in heavily populated cosmopolitan areas.

Also, Read: Flyover Design | Flyover Construction | Types of Flyover | What Is Flyover

Classification of Tunnel:

• Based on the purpose of the tunnel :
  1. Traffic tunnels
  2. Conveyance tunnels
• Based on the type of material for the construction of the tunnel :
  1. Tunnel in hard rock.
  2. Tunnel in soft rock.
  3. Open cut tunnel.
  4. The tunnel underneath the river bed or submarine tunnel.
  5. Tunnel in quicksand.
• Based on the alignment of the tunnel :
  1. Saddle and base tunnel.
  2. Spiral tunnel.
  3. Off spur tunnel.
  4. Slope tunnel.
• Based on the shape of the tunnel :
  1. Circular tunnel.
  2. Egg-shaped tunnel.
  3. Horseshoe tunnel.
  4. Elliptical tunnel.
  5. Vertical walls with arch roof type.
  6. Polycentric.

Also, Read: What Is Folded Plate | Folded Plate Structure | Folded Plate Roof Construction Details | Folded Plate Staircase | What Are Folded Plate Roofs

Advantages of Tunnels:

• Tunnels enable rapid but unrestricted transport in large congested cities.
• Tunnels shield the system (railway track, highway, sewage line, oil line, respectively.) under which it is built from changing weather including snow, fog, and so forth. As a result, tunnels minimize device operating costs.
• Tunnels prevent issues with surface life including traffic throughout construction.
• Tunnels shield the device from damage by bombs during the war.
• At some point, tunnels have proven cheaper to cross the mountain or river than open cut or bridges.
• In its most heavily developed urban area, underground rail or highways is the safest choice for the availability of modes of transport.
• In soft-rock, the tunnel construction became cheapest than that of the open-cut due to the significant amount of drops, respectively.
• Make unnecessary circuit routes across a mountain or a spur.
• Tunnel escapes a risky open-cut quite close to a structure.
• Tunnels are also proven economical to carry publicly owned utilities such as water, electricity, sewers, and so on.
• Unless the tunnels are equipped with a simple gradient, the transport costs can be minimized.
• The protection of tunnel construction also improved tremendously thanks to the advanced modern construction process.
• The reduction of distance tunnels has proven to be economical
• It diverts water for power generation Makes fast gradients in mountainous terrain resulting in high velocity of vehicles.

Also, Read: Pile Cap Design | Pile Cap Construction | Piles Structure | Pile Cap Foundations | Square Piling Caps | Pile Cap Reinforcement

Disadvantages of Tunnels:

• There is more to the initial investment of tunnel construction.
• The construction of tunnels requires skilled labour and high-level professional oversight.
• The length of the building of tunnels seems more than bridges or open sections.
• The design of tunnels includes the production of sophisticated and specialized machinery.

Also, Read: Reinforced Concrete Frame | Concrete Frame Construction | Concrete Building Construction | Frame Construction | Types of Frame

Applications of Tunnels:

• Utility tunnels are being used for steam routing, cooling water, electrical or telecommunication wires, such as for linking buildings for easy movement of people including equipment.
• Secret tunnels are designed for military applications, or through civilians for weapons, contraband, or human smuggling. Special tunnels, including such wildlife crossings, are designed to enable wildlife to cross man-made obstacles securely.

Also, Read: What Is Bridge Abutment | 5 Types of Abutments

Tunnel Construction Methodology:

Tunnel construction methodology are as follows.

• Cut and Cover Tunnelling.
• Drill and Blast.
• Bored Tunnelling by Tunnel Boring Machines (TBM).
• Sequential Excavation Method.

1. Cut and Cover Tunnelling :

Cut and cover tunnelling is a popular and quite well method for the construction of shallow tunnels. The system can handle variations in tunnel diameter and nonuniform forms but is frequently used in the design of underground stations.

A few simultaneous activities are planned to be carried out to use this tunnelling technique. Trench drilling, tunnel building and soil covering of excavated tunnels are three main integral parts of the tunnelling process.

Many of these activities are identical to other roadway construction, other than that the amounts of drilling involved are deeper. Bulk drilling is mostly carried out under a road deck to reduce traffic disturbance and effects on the environment in respect of noise pollution and visual impacts.

2. Drill and Blast:

Such a tunnelling technique requires it’s use of explosives. Drilling rigs are being used to dig blast holes mostly on planned tunnel surfaces to a specified blast depth. Explosives and timed detonators (delay detonators) then are put in the blast hole.

Since blasting, the waste rocks as well as soils are transferred out from the tunnel more before blasting. Almost all of the tunnel building in rock includes land somewhere between 2 harsh environments of hard rock and soft earth. Appropriate structural support mechanisms are also needed whenever this tunnelling technique is implemented.

3. Bored Tunnelling by Tunnel Boring Machines (TBM):

Boring tunnelling to use the Tunnel Boring Machine (TBM) is also used for the excavation of long tunnels. A successful TMB approach involves the collection of suitable equipment for various rock masses and geographical features.

The TBM could be ideal for the excavation of tunnels containing competent rocks that could provide sufficient geological stability for the digging of a long tunnel lacking structural support.

That being said, incredibly hard rock can create considerable wear of the TBM rock cutter and therefore can stop suddenly the advancement of tunnelling operations to the point that the TBM becomes unreliable and unprofitable and therefore can take much longer than that of the drill-and-blast tunnelling process.

4. Sequential Excavation Method:

Such a system has been identified as the new Austrian tunnelling method (NATM). Initially, the excavation site of the planned tunnel is split into parts. The fragments will then be consecutively extracted only with supports.

Any mining equipment, like roadheads and backhoes, is widely used only for tunnel excavation. The excavation field must’ve been entirely dry for the application of NATM, and ground dewatering is indeed an important pre-excavation method.

A further mechanism related to land changes, including such grouting and ground freezing, is also typical to this system in order to stabilize the soil for tunnelling. This approach is relatively sluggish but is considered to be effective in locations where existing systems, such as sewers or subways, could not be moved.

Also, Read: How Are Bridges Built | How Are Bridges Constructed | Factors Associated with Building Bridges

---