How Does a Tunnel Boring Machine Work?

A tunnel boring machine works by rotating a cutting-head at the front of a tube shaped body the size of the tunnel. Ground material passes through the body and is removed from the tunnel by a conveyor belt.

A tunnel boring machine is held in place by a series of hydraulic plates attached around its body. The plates not only stabilize the machine but also support the freshly bored tunnel. Hydraulic plate support also allows the machine to move forward and apply pressure to the cutting-head. The cutting-head is disc-shaped and consists of cutting plates and hoppers. The cutting-head rotates 360 degrees, loosening material and grinding stone into chips, which fill the hoppers. The hoppers dump the material onto a conveyor belt which removes it from the boring area and transfers it to a dump site at the rear of the tunnel. Dump trucks remove the chips from the dump site as the process continues.

The rear of the boring machine is fitted with equipment to stabilize the tunnel as the machine moves along. From a rear platform, steel bolts and wire mesh are attached to the tunnel wall. A concrete mix called shotcrete is then sprayed on the wall to give the fresh tunnel support.