Tunnel it’s a concept that comes from the English word tunnel. It is a underground way which, in general, is artificially opened in order to allow communication between two places. In some cases, tunnels are created by action of nature.
For instance: “The provincial government is building a tunnel in the hill to facilitate the access to the town of Pucalpé “, “They should improve the signaling of the tunnel to avoid accidents”, “One of the most important projects for the next few years is the construction of a subfluvial tunnel that connects both provinces”.
The tunnels allow the transfer of merchandise and of persons, although its characteristics are varied. There are tunnels only suitable for pedestrians, others that allow the passage of cyclists and some enabled for motor vehicles (such as cars, trucks, etc.). There are even tunnels specially designed for the passage of the train.
Tunnels are sometimes built on undeveloped natural terrain to improve the communication. A tunnel, in this sense, can be built in a mountain to facilitate the passage of vehicles without the need for them to surround the elevation or have to climb its surface. The development of the tunnel, of course, requires an exhaustive study to analyze its viability.
In the cities, tunnels are used for burying the railroad or for underground transport services such as the subway, to name two possibilities.
If we focus on the soccer, finally, it is known as tunnel, spout or cassock to the play that consists of passing the ball between the opponent’s legs.
There is a construction method called false tunnel used in works that begin with an excavation in the surface of all or almost all the space that will be allocated to the tunnel, to carry out the open-cast construction and then cover it once it is finished. In this case, it is necessary to have a system capable of sustaining the structure and their respective charges.
It is possible to distinguish between two variations of this method, according to the order in which the works are carried out:
* bottom up (“From the bottom up”): as stated above, the first step is to excavate to reveal the extension that the tunnel will occupy. Then proceed with the plays from the interior, making the concrete there or carrying prestressed concrete, arches with corrugated or prestressed steel, or brick (the most common material of the first false tunnels);
* top down (“From top to bottom”): Unlike the previous method, this one consists of digging a trench and pouring it from the surface to build the tunnel walls, and continuing with the upper slab once these have been completed. In this way, only the hole necessary to mount the slab on the walls. Finally, the surface must be rebuilt, even before all interior work is finished.
It is worth mentioning that the method top down It is the most used today to build tunnels in the urban areas. Among its advantages over the other is the fact that it does not require the use of specialized machines. On the other hand, it also allows the creation of tunnels with more than one floor, through the use of intermediate slabs.
To automate the tunnel creation process, the tunnel boring machines, which are associated systems forward and reverse. There are many kinds of tunnel boring machines, and each of them is adapted to a different type of work and to the conditions of the job site (for example, the soil can be disintegrated or dense rock, among other possibilities, and this brings different challenges) .