How does Tunnel Boring Machine (TBM) work? A Tunnel Boring Machine (TBM) is a specialised piece of equipment used to excavate tunnels through various types of soil and rock. It works by using a rotating cutter head with sharp disc cutters or tools that grind away the material in front of it, creating a tunnel of a precise diameter. As the cutter head rotates, the TBM simultaneously removes excavated material through a conveyor system and supports the newly created tunnel walls with precast concr