How Much Does a Tunnel Boring Machine Cost?
A tunnel boring machine, also known as a mole, is a machine with a circular cross section used to dig tunnels and excavate through different soil and rock varieties. Some tunnel boring machines measure as big as 428 feet long.
While tunnel boring machines are highly useful in drilling, blasting, and construction purposes, they are very expensive to construct, require significant infrastructure, and can be difficult to transport. Most tunnel boring machines used are owned by construction corporations, rental companies, or by the city road commissions.
How much does it cost?
- An article at EquipmentWorld.com states that the world’s largest tunnel boring machine, called Big Bertha, cost $80 million. It was constructed by Seattle Tunnel Partners.
- According to the Florida Department of Transportation, the cost of a tunnel boring machine is $45 million. The Port of Miami Tunnel project is set to use the machine built particularly to work in the geological conditions of specific locations.
- In Oregon, a tunnel boring machine was used to build the East Side Big Pipe. According to the city of Portland, Oregon, the machine, nicknamed Rosie, cost $12 million. The equipment, which was manufactured in Schwanau, Germany in 2006, weighed 530 tons. It was shipped in sections from Germany to the Port of Vancouver in 2007.
What is going to be included?
- Tunnel boring machines, such as Bertha, are extremely massive and need to be assembled from a number of parts. Because of the size, the tunnel boring machine will be disassembled for transportation and then reassembled at the site of the job. With Bertha, the largest part weighed 900 tons. There are different types of tunnel boring machines. When digging in hard rock, an open-type or shielded tunnel boring machine can be used. When excavating soft ground, the three kinds of machines used are the open-face type, the earth pressure balance machine, or a slurry shield. The machines can either be single or double shielded. The choice is dependent on the kind of rock strata and the needed speed of excavation.
- According to Wikipedia, “Modern tunnel boring machines typically consist of the rotating cutting wheel, called a cutter head, followed by a main bearing, a thrust system and trailing support mechanisms. The type of machine used depends on the particular geology of the project, the amount of ground water present and other factors.”
What are the extra costs?
- Using, building, and transporting a tunnel boring machine is not an easy task. You will need to hire many people and pay them for their work. None of this manpower is covered by the purchase of the machine.
Tips to know:
- The Bertha tunnel boring machine is the world’s largest to date, measuring 326 feet long and 57.5 feet wide. It is made with 7,000 tons of steel and machinery, having an 80-ft deep launching pit in the place where it was assembled. The machine uses 25,000 bhp (18,600 kW) and moves 35 feet (10 meters) per day.
- A tunnel boring machine, after it is unloaded from a ship, can take up to three months to be put together. It is usually delivered in pieces and taken to the location where excavation is scheduled. The contractor digs a pit and assembles the machine in the hole. Excavation typically starts where the machine is assembled.
- When the tunnel boring machine is at work, there is a large amount of “muck,” which are all the rock pieces and chips that are left behind. These are sometimes used for other parts of the project, sometimes sold to landscaping and other companies, or other times just disposed of since it is unusable.
How can I save money?
- Tunnel boring machines are naturally expensive, but experts say that the cost of the machines against the cost of drilling and blasting increasingly longer tunnels is actually less. The reason is that tunneling using these tunnel boring machines is a lot more efficient and helps in completing projects in a shorter period of time.
- The cost of a tunnel boring machine is obviously higher the bigger it is. In order to save money, the choice is often to go with a smaller machine that can still perform the needed tasks.
- Rather than purchasing a tunnel boring machine, you can choose to rent one from a company which owns one. If you only need it for one project, this is a good option. However, if you are going to use it multiple times, you would be better off purchasing one.