What Does tunnel Mean
Tunnel is a concept that comes from the English word tunnel . It is an underground road that, in general, is artificially opened in order to allow communication between two places. In some cases, tunnels are created by action of nature.
For example: "The provincial government is building a tunnel in the hill to facilitate 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 linking both provinces ” .
The tunnels allow the transfer of goods and people , although their 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 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 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 football , finally, it is known as a tunnel , pipe or cassock to the play that consists of passing the ball between the opponent's legs.
There is a construction method called a false tunnel used in works that begin with an excavation in the surface of all or almost all the space that will be used for 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 supporting the structure and its respective loads.
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 extent that the tunnel will occupy. Then we proceed with the interior works , manufacturing 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 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 must be excavated . Finally, the surface must be rebuilt, even before all interior work is finished.
It is worth mentioning that the top down method is currently the most used to build tunnels in 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 process of creating the tunnels are used TBM , which are associated with systems of 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) .