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A tunnel boring machine (TBM), also known as a "mole" or a "worm", is a machine used to excavate tunnels. Tunnels are excavated through hard rock, wet or dry soil, or sand, each of which requires specialized technology. Tunnel boring machines are an alternative to drilling and blasting (D&B) methods and "hand mining".
Construction began in July 2013 using "Bertha", at the time the world's largest earth pressure balance tunnel boring machine, with a 17.5-metre (57.5 ft) cutterhead diameter. After several delays, tunnel boring was completed in April 2017, and the tunnel opened to traffic on 4 February 2019.
The plausibility of such machines has declined with the advent of the real-world tunnel boring machines, which demonstrate the reality of the boring task. Tunnel boring machine themselves are not usually considered to be subterrenes, possibly because they lack the secondary attributes – mobility and independence – that are normally applied ...
Freighter Fairpartner carrying the disassembled tunnel boring machine into the Port of Seattle in April 2013. Bertha was designed and manufactured by Hitachi Zosen Sakai Works of Osaka, Japan, and was the world's largest earth pressure balance tunnel boring machine, [14] at a cutterhead diameter of 57.5 feet (17.5 m) across.
Boring is drilling a hole, tunnel, or well in the Earth. It is used for various applications in geology, agriculture, hydrology, civil engineering, and mineral exploration. Today, most Earth drilling serves one of the following purposes: return samples of the soil and/or rock through which the drill passes; access rocks from which material can ...
Tunnel Construction. Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the ground water conditions, the length and diameter of the tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and shape of the tunnel and appropriate risk management.
The mole itself is a steel cylinder about 60 cm long and 6 cm in diameter. It works as a pneumatic cylinder with pulsed compressed air causing the head of the mole to repeatedly hammer against the soil in front of the mole. Once the mole has passed through the earth the pipe can be pulled through the long horizontal hole.
A tunnel boring machine (TBM) consists of a shield (a large metal cylinder) and trailing support mechanisms. A rotating cutting wheel is located at the front end of the shield. Behind the cutting wheel there is a chamber where the excavated soil is either mixed with slurry (so-called slurry TBM) or left as-is (earth pressure balance or EPB ...