Tunnel Boring Machines. These massive machines are essentially moving factories that cut through the rock, excavate the waste out of the back, and install the concrete shielding, all while pushing itself along like an inchworm.
Video courtesy of CDM/HMM Joint Venture - For engineering enthusiasts and anyone who's interested in the mechanics of siphon construction, this animation shows exactly how the 110-ton, 300-foot-long tunnel boring machine will drill a distance of nearly two miles, 100 feet beneath the New York Harbor seabed. Find out more about the Staten Island ...
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 can bore through anything from hard rock to sand. Tunnel diameters can range from a metre (done with micro-TBMs) to 19.25 m to date. Tunnels of less than a metre or so in diameter are typically done using trenchless construction methods or horizontal directional drilling rather than TBMs.
This is how a tunnel boring machine will burrow a viaduct under Seattle