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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.
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.
The end of a sentence. ¶ Pilcrow: Paragraph mark, paragraph sign, paraph, alinea, or blind P: Section sign ('Silcrow') ⌑ Pillow (non-Unicode name) 'Pillow' is an informal nick-name for the 'Square lozenge' in the travel industry. The generic currency sign is superficially similar | Pipe (non-Unicode name) (Unicode name is "vertical bar ...
Business letters can have many types of content, for example to request direct information or action from another party, to order supplies from a supplier, to point out a mistake by the letter's recipient, to reply directly to a request, to apologize for a wrong, or to convey goodwill. A business letter is sometimes useful because it produces a ...
Lindsay Clancy, the Massachusetts mother accused of strangling her three young children to death before attempting to kill herself, is seeking an insanity defense, court records show.
Federal officials warned Tuesday that a massive Chinese hacking operation against American telecommunications companies hasn’t yet been fully expelled and that the best way to hide ...
For his Education Secretary, Trump has picked Linda McMahon, the co-founder of World Wrestling Entertainment, who served as head of the U.S. Small Business Administration during Trump’s first term.