What are the three types of tunnels? Three Common Types of Tunnels.
1. Transportation Tunnels
These are designed for vehicles, trains, or pedestrians. Examples include subway tunnels (e.g., shield-driven metro tunnels mentioned in ), road tunnels, and ice tunnels carved for exploration or military use (as seen in the "Manuscriptorium Ice Tunnels" and "Camp Tuto Ice Tunnel" from ). Shield tunneling, a method frequently used in metro projects, ensures structural stability in urban environments.
2. Hydraulic Tunnels
Built for water conveyance, drainage, or hydropower systems. These tunnels often pass through mountains or under rivers. For instance, meltwater streams flowing through glacial ice tunnels form natural hydraulic structures called "eskers" (referenced in ).
3. Mining Tunnels
Used in resource extraction, such as coal or mineral mining. These tunnels require reinforcement to withstand geological pressures and are typically narrower than transportation tunnels.
Three types of tunnels according to construction methods
1. Cut-and-Cover Tunnels
These are built by excavating a trench from the surface and then covering it over. They’re generally used for shallow depths.
2. Bored Tunnels
Constructed deep underground using tunnel boring machines (TBMs) or the drill-and-blast method, these tunnels are ideal for urban areas or where surface disruption must be minimized.
3. Immersed Tube Tunnels
These involve prefabricated tunnel segments that are sunk into a pre-dredged trench—commonly used for underwater crossings.
What is the best shape for a tunnel?
Optimal Tunnel Shape
The circular shape is widely regarded as the most efficient for tunnel construction due to:
1. Structural Integrity: Circular tunnels evenly distribute external pressure from surrounding soil, rock, or ice, minimizing stress points. This is critical in shield-driven tunnels and ice tunnels , where stability is paramount.
2. Construction Feasibility: Shield tunneling machines (used in metro projects) are designed to excavate circular sections efficiently. The shape also simplifies lining installation.
3. Versatility: Suitable for diverse environments, including soft soil, hard rock, and glacial ice.
While other shapes like rectangular (for pedestrian underpasses) or horseshoe (for mountain rail tunnels) exist, they are less optimal for high-pressure environments.