Definition - What does Can mean?
The can is safety zone inside a large tunnel boring machine (TBM). Located behind the shield and the cutterhead bulkhead, the can is reminiscent of, well, a tin can ladle on one side and open on one end as a TBM creeps through the tunnel. The can provides sufficient space to secure the entire crew in the case of the cave in. This means that the can may be made of more than one section and may be articulated.
Trenchlesspedia explains Can
The can is designed to provide a temporary safe haven for the crew of a TBM be trapped by a tunnel cave in. It may consist of one or more modular units, its walls are generally steel and as strong or stronger than safety shield that makes up the forward wall of the can. Smaller cans may protect 20 people larger cans may protect up to 75 persons these larger TBM's also have escaped drilling units to help the occupants leave the can in an expeditious manner.