How will the tunnel boring machine work on the Great Lakes Tunnel Project?

Our Answer

The tunnel boring machine (TBM) is like a giant drill that drills through the earth to make tunnels for various kinds of infrastructure. The main part of the machine is called the shield which is like a circular can. In front of the shield is the cutter head which rotates and breaks up the ground which is then transported out of the tunnel. In the back part of the shield concrete segments are installed that form a circular lining to support the ground and seal the tunnel. The TBM advances turning in a circle, then builds a ring of concrete lining segments, pushes forward, then stops to build a ring, repeating the process until the tunnel is completed.

The type of tunnel boring machine we are using is designed for the job specific ground conditions and will be operated in a pressurized mode or closed mode—essentially operating like a “submarine,” sealed off from the surrounding ground and water—in a controlled manner to remove the ground.

The amount of material excavated will be continuously monitored. There are sensors on the machine which provide data on TBM performance which will be continuously monitored and operations adjusted.

The TBM is designed so that during excavation no ground is exposed and all workers work within the shield or the lined tunnel—which supports and seals off the workspace from the outside.