*A tunnel boring machine (TBM) is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through hard rock, sand, and almost anything in between. Tunnel diameters can range from a metre (done with micro-TBMs) to 19 metres. Tunnels of less than a metre or so in diameter are typically done by horizontal directional drilling rather than TBMs.
Tunnel boring machines are used as an alternative to drilling and blasting (D&B) methods in rock and conventional 'hand mining' in soil. A TBM has 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, difficult to transport and require significant infrastructure. The biggest is built by Herrenknecht AG of Schwanau, Germany to dig the 57 km Gotthard Base Tunnel. It has a diameter of 19 meters.
************************************************************************************
aku tak puas hati dengan sistem perparitan kat kawasan kedai aku ni. asal hujan lebat je air masuk dalam kedai. letih la aku nak kena mop dengan punggah pc letak atas meja. aku dah start kumpul duit nak beli mesin kat atas ngan lantik kontraktor dari jepun. lepas ni indah water pun kena bayar kat aku kalau nak pakai aku punya longkang.
moral: sediakan payung sebelom hujan, sediakan longkang sebelom banjir
No comments:
Post a Comment