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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.
Teesside Beam Mill (TBM) is a steel reheating and rolling plant located at Lackenby, on Teesside, North Yorkshire, England. The plant was set up in the 1950s by the Dorman Long company and began full production in 1958, making beams for building projects. The plant produces around 750,000 tonnes (830,000 tons) of steel products per year, and is ...
The decision whether to construct a tunnel using a TBM or using a drill and blast method includes a number of factors. Tunnel length is a key issue that needs to be addressed because large TBMs for a rock tunnel have a high capital cost, but because they are usually quicker than a drill and blast tunnel the price per metre of tunnel is lower. [ 2 ]
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 shield), depending on the type of the TBM. The choice of TBM type depends on the soil conditions.
Its products have often pushed technological boundaries; a Herrenknecht-built TBM in the late 1990s was the largest in the world at that time, while the world's longest and deepest railway tunnel (the Gotthard Base Tunnel) was bored using the company's apparatus. By 2015, the company had around 5,000 employees.
It is a rapidly growing sector of the construction and civil engineering industry. It can be defined as "a family of methods, materials, and equipment capable of being used for the installation of new or replacement or rehabilitation of existing underground infrastructure with minimal disruption to surface traffic, business, and other activities."
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If the station box is built before the TBM passes through, the TBM would drill through the side of the station box, would have to be moved to the other side of the station box where it would restart the tunnel boring process. Station box construction methods have been used in a wide variety of subway and metro projects.