Tunnels: How They are Made
Tunnels are everywhere on the planet. There is natural forming tunnels as well as many manmade tunnels that are used for a number of reasons. But, how is it that man can make these great underground masterpieces without them caving in? What are tunnels dug with?
A lot of manmade tunnels are used to reduce time for traffic or trains traveling to and fro across the country. A lot of them supply water to many towns and cities as well as provide a way to turn the rivers so they pass through dams to create electricity. Some are used for sewers and telecommunication lines that span the globe.
Without the creation of tunnels life would be very different on the surface. Humans often take these great feats of technology for granted. We will take a look at the ways in which tunnels are made and some of the ways in which they are used in a series of articles so make sure you stay tuned in. First we are going to look at how tunnels are created and what is use to create them.
Beginning in the early nineteenth century they were still digging tunnels by way of dynamite and hand. Workers would blow up a section and then clear it out in the process. It was not until the early eighteen hundreds when they were digging the themes river that the first boring machine was used. Tunnel boring machine (TBM) also known as a "mole" this drastically reduced the manpower as well as the time that it took to dig a tunnel using the new boring machines. The modern boring machine typically uses a rotating cutting wheel called a cutter head. It is then followed by a rotating bearing and support machinery. The cutting machines also very depending on the type of digging that you are doing from granite to shale.
Drilling and Blasting:
This is the old fashioned way of getting into tunnels that is still used heavily today. With shorter tunnels it is more expensive to bring in a boring machine so construction by drilling and blasting are more economical. There are precise measurements completed by a topographer and they the dynamite is put into holes with varying degrees of length. Once the dynamite is explored it loosening the rock at that entrance points and forces it to collapse. Which is then cleared out and the process starts over for the next section.
Cut & Cover:
This type of tunnel drilling is commonly used for very small tunnels that need to be dug. For example if a sewer line is being put in on a road they will typically dig a trench and then it is covered over with a roof support system. The overhead is then adjusted and built to spec to hold the weight of hat is being built over it.
Tunnel making has come a long way since the early days. Creating smaller tunnels for water or sewer pipes can also be made using the pipe jacking method. The crew working it will usually take a solid pipe and use hydraulic jacks to help support the tunnel after a smaller scale boring machine is in front cutting out the tunnel. This is usually under roads or railroads where the main lines need to be connected to one another.
Box jacking is known as tunnel jacking like the previous. It involves the placement of rectangular shaped sections using a hydraulic jack. Usually the rectangular cutouts are pre made and brought to the site which is then forced into position using the hydraulic jack. So the ground must be soft enough to push their way through the soil. There are a lot of these types of constructions where there is existing road over head or building that cannot be moved through regular drilling.
This is typically a manual process lots of people are digging their way to a specific location. Many of the army’s during world war one and world war two used this method to either dig trenches or tunnels into enemy lines without being noticed. It was very efficient way to avoid detection.
With all the advancements of tunneling there is still in use some of the old techniques. But it is still amazing the things that we can create just by digging.