Why are subways built underground?

Why are subways built underground?

Subway, also called underground, tube, or métro, underground railway system used to transport large numbers of passengers within urban and suburban areas. Subways are usually built under city streets for ease of construction, but they may take shortcuts and sometimes must pass under rivers.

How long does it take to build a subway tunnel?

Most rapid transit lines take an average of 5 years to as long as 15 years sometimes depending upon the capital available and the land acquisition. However some metro systems can be built within a short time as well.

How underground metro is constructed?

Underground metro stations are constructed with cut and cover technologies. There are two methods in cut and cover technique which are Top Down construction and Bottom Up construction.

What is the oldest underground in the world?

The Metropolitan line The Metropolitan line is the oldest underground railway in the world. The Metropolitan Railway opened in January 1863 and was an immediate success, though its construction took nearly two years and caused huge disruption in the streets. Read more about the Metropolitan line.

What is the most common shape of subway tunnels?

circular They are usually circular and go straight down until they reach the level at which the tunnel is going to be built. A shaft normally has concrete walls and is usually built to be permanent. Once the access shafts are complete, TBMs are lowered to the bottom and excavation can start.

How deep do subway tunnels go?

about 50-70 feet Tunnel Overview Tunnels are typically about 20 feet in diameter. There are two parallel tunnels separated by about 20 feet, one tunnel for train travel in each direction. Tunnels are generally about 50-70 feet deep, though they can be deeper between stations.

How long do you toast a subway sandwich?

The Time Required For The Subway Toast The Sandwiches. The maximum time required is 20 to 25 seconds. Subway uses the heat convection to toast the sandwich. The scorching air passes around the sandwich like a storm.

What do they use to make subway tunnels?

We'll take a look at some of these in the next section. After digging subway tunnels, workers use a variety of materials to make them waterproof. Common historical methods included lining tunnel floors with gravel, applying waterproof material coated in concrete and lining the tunnel with asphalt and brick.

How are the New York City subways built?

Subways are built with an extensive series of fans, ventilation, and airshafts to operate a ventilation system. Natural air circulation isn’t enough to keep temperatures regulated, let alone keep the air breathable while also controlling smoke movement throughout the tunnel.

What kind of equipment is used to build subways?

Typical trenching equipment is utilized for the cut and cover method to dig up and construct the tunnel and its various parts. Afterward, the street is put back into place, leaving the tunnel underground.

How are tunnels dug in New York City?

Some tunnels are drilled with tunnel boring machines (TBMs), while others are mined out in a progressive excavation technique called sequential excavation method (SEM). Also known as the Austrian method, SEM is used to mine out specific sections of the tunnel while keeping the ground stable during the mining.