What is a tunnel excavator?  A tunnel excavator is a specialized piece of heavy equipment used for digging and constructing tunnels. It typically consists of a rotating cutting head mounted on a machine that moves forward as it excavates, breaking through rock, soil, or other materials. These machines are often used in large-scale infrastructure projects such as subway systems, highways, or railway tunnels.

　　A tunnel digging machine is most commonly referred to as a Tunnel Boring Machine (TBM) . TBMs are large, cylindrical machines equipped with rotating cutting discs that can bore through various types of ground, including soft soil, hard rock, and mixed ground. They are designed to create tunnels with smooth walls, reducing the need for additional lining or finishing work. TBMs are typically used for projects where precision and safety are critical, like in urban areas.

　　There are also other types of tunnel excavating equipment, such as roadheaders and drill-and-blast methods used for specific types of tunnels or ground conditions, but TBMs are the most widely recognized for large-scale tunnel construction.