The shield TBM features a cylindrical shell structure, which means that the machine is compatible with a wide range of geological conditions, from hard rock to weak stratum. Above all, it is capable of tunneling defective ground. There are two types of shield TBM. One is double-shield TBM, which can be driven forward by the main gripper. The other is single-shield TBM, which is driven forward by the shield only.
The open TBM features a simple structure, which enables the machine to excavate stable rock efficiently. It is driven forward primarily by the main gripper and allows tunnel support immediately after the face and supplementary construction method. It is used for the high-speed excavation of hard rock parts.