Tunneling is crucial for modern infrastructure projects, allowing for efficient travel routes and essential infrastructure such as hydroelectric dams. Tunnel boring machines (TBMs) have become the go-to method for tunneling through a variety of ground conditions, evolving from earlier shield designs. TBMs can be closed or open, depending on whether they require support for the tunnel face. Other innovations, such as the use of bentonite slurry or EPS machines, have made tunneling through soft ground faster and more environmentally friendly. The development of precast concrete linings has also revolutionized tunnel construction, while rock tunneling has historically relied on drill and blast methods until the advent of mechanized rock tunneling machines in the 1950s.
https://www.construction-physics.com/p/the-evolution-of-tunnel-boring-machines