隧道 工程项目英语.docx

8.1.5 tunnel type of tunnel.1 classified by construction method1Cut and cover tunnel 2Dill and blast tunnel 3TMB tunnel 4Sunken tube tunnel .2 classified by shape of cross-section1Single tunnel 2Twin tunnel 3Tri-tunnel construction method.1 constructionprocedure.2 TBM methodWhat tmbis:A?tunnel boring machine?(TBM), also known as a mole, is a machine used to excavate?tunnels?with a circular cross section through a variety of soil and?rock strata. They may also be used for?microtunneling. They can?bore?through anything from hard rock to?sand. Tunnel diameters can range from a metre (done with micro-TBMs) to 19.25 metres to date. Tunnels of less than a metre or so in diameter are typically done using?trenchless construction?methods or?horizontal directional drillingrather than TBMs.What parts included in TMBModern TBMs typically consist of the rotating cutting wheel, called a cutter head, followed by a main bearing, a thrust system and trailing support mechanisms.What soil conditions applied inIn hard rock, either shielded or open-type TBMs can be used. All types of hard rock TBMs excavate rock using disc cutters mounted in the cutter head. In fractured rock, shielded hard rock TBMs can be used, which erect concrete segments to support unstable tunnel walls behind the machine.In soft ground, there are three main types of TBMs: Earth Pressure Balance Machines (EPB), Slurry Shield (SS) and open-face type. Both types of closed machines operate like Single Shield TBMs, using thrust cylinders to advance forward by pushing off against concrete segments.Merit and weakness TBMs have the advantages of limiting the disturbance to the surrounding ground and producing a smooth tunnel wall. This significantly reduces the cost of lining the tunnel, and makes them suitable to use in heavily urbanized areas. The major disadvantage is the upfront cost. TBMs are expensive to construct, and can be difficult to transport. TBMs is much more efficient and results in shortened completion ti