The working principles of Tunnel Boring Machines (TBMs) and Shield Tunneling Machines (Shield TBMs) are fundamentally different, and each is suited to specific tunneling environments and requirements.

　　I. Working Principles

　　TBM Working Principle:

　　- TBMs cut through the tunnel wall using a rotating cutterhead. The debris generated from the cutting process is transported out of the tunnel using conveyors or elevators.

　　- The machine advances through a hydraulic propulsion system, pushing it forward in a relatively stable environment.

　　Shield TBM Working Principle:

　　- Shield TBMs excavate tunnels under the protection of a shield shell. The shell provides support and creates a workspace for installing precast tunnel linings.

　　- The front end of the shield TBM features a rotating cutterhead that cuts through the tunnel wall, while an integrated installation system places the precast segments onto the excavated tunnel's inner walls.

　　- The propulsion and sealing systems of shield TBMs work together to ensure safety and stability during the excavation process.

　　II. Differences in Working Principles

　　1. Cutting and Advancing Mechanisms:

　　- TBMs rely solely on physical cutting of the tunnel wall.

　　- Shield TBMs combine cutting with the simultaneous installation of precast linings, making them multifunctional.

　　2. Operating Environments:

　　- Shield TBMs are particularly suitable for challenging underground environments, such as urban areas and beneath rivers.

　　- TBMs are more flexible and can operate in a wide range of geological conditions.

　　3. Construction Efficiency:

　　- Shield TBMs generally offer higher efficiency due to their high level of automation and the integration of lining installation, particularly for long-distance tunnels.

　　4. Safety:

　　- Shield TBMs provide a more protective working environment, reducing the impact on surrounding areas and ensuring worker safety.

　　III. Application Scenarios

　　- Shield TBMs:

　　Shield TBMs are commonly used in projects requiring rapid construction and strict control over ground settlement, such as urban rail transit systems and highways.

　　- TBMs:

　　TBMs are better suited for projects with simpler geological conditions and shorter construction distances, such as mining tunnels and small-scale water conservancy tunnels.

　　Conclusion

　　The primary distinction between Shield TBMs and TBMs lies in the Shield TBM’s multifunctionality and adaptability to complex environments. Selecting the appropriate equipment requires a comprehensive evaluation of geological conditions, construction requirements, and budget considerations.