logo

Once the TBM has completed both tunnels, most parts from the trailing gear (gantries) will be sold back to Herrenknecht, the manufacturer, for reusing in other TBMs.  The other parts that cannot be resold, such as the shield and cutter-heard, will be recycled.
 

A tunnel boring machine (TBM) is used to dig tunnels. It consists of a cutter head and trailing gear that carries support equipment and moves excavated material out of the tunnel. The Port of Miami Tunnel project will use a TBM built specifically to work in the geological conditions of Government Cut and dig the two tunnels.

The total length of the TBM is 428.5-feet long (more than one football field), consisting of a 361 foot long trailing support gear made up of 6 gantries and a cutter head with an outside diameter of 42.3 feet (as high as a 4 story building).

• The cutter head rotates and bores out the underground area.
• The trailing gear contains the electrical, mechanical and guidance systems and additional support equipment.
• Excavated material is carried back through the trailing gear on a conveyor belt and deposited outside the tunnel entrance, or portal.
• As the TBM moves forward it puts up a precast concrete liner (segments that create a ring) in place that becomes the finished wall of the tunnel.
• Once the liner is in place, grout (a construction mixture) is pumped into the space between the liner and the excavated area to seal the tunnel in place.

The TBM uses eight segments per ring.

The TBM can place up to eight rings per day.

The two tunnels will require 12,000 tunnel segments.  The segments are being made at the Cemex concrete batch plant in Sweetwater, Florida.

The cost of the TBM is more than $45 million.

TBMs are a very specialized type of equipment and only a few companies in the world build them. The Port of Miami Tunnel TBM was built by Herrencknecht. Once completed, the machine was tested, disassembled and then shipped in pieces to the Port of Miami.

The machine’s heaviest parts arrived at the Port of Miami on a transatlantic ship on June 23, 2011. The rest of the pieces arrived by plane.

Once unloaded from the ships, the TBM was moved to Watson Island. It was put back together in the median of the MacArthur Causeway, where the contractor dug a hole, or pit. The machine began excavating there.

It took about three months.

The TBM began mining the first tunnel on November 11, 2011 and the TBM broke out on Dodge Island (PortMiami) on July 31, 2012.  The machine was then partially disassembled, turned around and reassembled and began mining in the Westbound direction towards Watson Island on October 29, 2012. Completion of the second tunnel is expected to be completed in Spring 2013.

There will be a crew of 12 to16 people working inside the TBM, and 12 to 14 on the surface.

The TBM operates 24 hours per day (20 hours alternating between excavating and ring installation and 4 hours stopped for maintenance).

The TBM is hydroelectrically powered and will be deep below the bottom of the channel, so the noise and vibration generated is not expected to be felt on the surface.