An Insight into Mechanized Tunneling with Tunnel Boring Machines

History has seen the evolution of tunnelling starting with cave formation, for water management, underground transportation, and mineral extraction and for warfare purposes. Tunneling technology has advanced since the 1950 from the conventional drill and blast techniques to the most advanced and sophisticated mechanized tunneling with tunnel boring machines. The range of scenarios in which tunnel boring machines are deployed is continuously expanding, from clays to granular soils to highly fractured or monolithic rock masses, from partially to fully saturated ground, and from mountain ranges with high overburden pressures to sensitive urban areas with low overburden. Today, the application range of tunnel boring machines is being extended to an ever increasing variety of geotechnical conditions. This review paper gives an overall perspective of tunneling with tunnel boring machines and suitability of tunnel boring machines for soft ground conditions