Shield tunneling machine is a tunnel boring machine using shield tunneling method. Shield construction method is tunneling machine in tunneling at the same time to build (laying) tunnel "shield" (refers to the supporting segment), it is different from the open construction
method. Internationally, generalized shield tunneling machine can also be used in rock formation, but different from the open (non-shield tunneling machine) tunnel boring machine. But in our country, the tunnel tunneling machine used for soft soil layer is habitually called the narrow sense shield machine, will be used for the rock formation to be called the (narrow sense) TBM. According to the working principle, the shield machine is generally divided into hand digging shield, extrusion shield, semi-mechanical shield (local pressure, global pressure), mechanical shield (open-chest cutting shield, pneumatic shield, mud and water pressure shield, earth pressure balance shield, mixed
shield, special-type shield).