Tunnel boring machines (TBMs) are essential equipment for tunnel and underground engineering excavation. Depending on whether the tunnel face requires pressure stabilization, TBMs can be categorized into open-type TBMs and pressurized TBMs. These two types play significant roles under different engineering conditions.

　　1、Open-Type TBMs

　　Open-type TBMs are suitable for tunneling environments that do not require special pressure stabilization. Their primary features include simple structure, easy operation, and low maintenance costs. These machines are widely used in tunnel projects with relatively stable geological conditions, such as hard rock and dry soil layers. The working principle of open-type TBMs involves mechanical breaking or cutting to achieve tunnel excavation, making them ideal for medium to short-distance tunnel projects.

　　2、Pressurized TBMs

　　Pressurized TBMs are used in complex geological environments requiring pressure stabilization, such as soft soil, sand layers, and underwater tunnels. These machines apply pressure to the tunnel face to prevent collapses or water ingress during excavation. Pressurized TBMs have complex internal structures, including pressure chambers, sealing systems, and slurry treatment systems, allowing them to work safely and efficiently under high water pressure and high ground stress conditions.

　　Comparison of the Two Types of TBMs

　　There are significant differences between open-type TBMs and pressurized TBMs in terms of application scenarios, structural complexity, and costs. Open-type TBMs are suitable for projects with simpler geological conditions and offer advantages of lower cost and easier maintenance. In contrast, pressurized TBMs have irreplaceable advantages in complex geological conditions. Although their costs are higher, they effectively ensure the safety and progress of the project.

　　TBMs play a crucial role in tunnel and underground engineering. Choosing the right type of TBM based on specific project requirements can significantly enhance construction efficiency and safety. In future tunnel projects, as technology continues to advance, TBMs will become more intelligent and efficient, further driving the development of underground engineering.