Tunnel boring machine | PPT
WEBOct 27, 2016 · 1) Tunnel boring machines (TBMs) are used to excavate tunnels with a circular crosssection through various ground types and diameters ranging from 120 meters. 2) A TBM consists of one or two large metal cylinder shields at the front, fitted with a cutting wheel, and hydraulic jacks that push the machine forward as it removes material.