Used to describe deposits left by the partial evaporation of infiltrating groundwater containing dissolved salts. CanA principal module that is part of a shield machine such as an MTBM or tunnel boring machine (TBMs); its use depends on the installation dimensions required and the presence of an articulated joint to facilitate steering. The can may also be referred to as a trailing tube. be classified into light, medium or heavy by percentage loss of cross-sectional area.