How are tunnel boring machines steered? Tunnel Boring Machines (TBMs) are steered using a combination of several technologies and control systems to ensure they follow the designed tunnel alignment accurately. The steering of a TBM involves three main components: guidance systems, hydraulic jacks, and articulated cutterheads or shield segments.

　　Here’s how the process works:

　　1. Guidance Systems

　　- Laser Guidance: TBMs typically use laser guidance systems to steer. A laser beam is projected from a fixed point at the tunnel’s entrance and reflects off a target located inside the TBM. The position of the beam relative to the target helps determine if the TBM is off-course.

　　- Gyroscopic Navigation: For longer tunnels where a straight laser beam isn't feasible, gyroscopes are used to measure the machine’s orientation in space, helping operators adjust the TBM’s trajectory.

　　- Surveying Instruments: Before and during tunneling, precise survey data are collected to provide the machine operators with real-time updates about its position and direction.

　　2. Hydraulic Jack Control

　　TBMs use a series of powerful hydraulic jacks to push against the already-installed tunnel segments or the surrounding ground to propel the machine forward. These jacks can be adjusted individually, allowing the operator to slightly alter the direction of the machine as it progresses through the ground. By extending or retracting certain jacks more than others, the TBM can be made to turn, rise, or fall.

　　3. Articulated Shield/Cutterhead

　　Many TBMs have an articulated shield or a cutterhead that can be tilted slightly to adjust the machine's direction. This articulation allows for gradual changes in the tunnel’s direction without requiring the machine to stop.

　　4. Automatic and Manual Steering

　　TBMs are equipped with both manual and automatic steering modes. In automatic mode, the machine follows pre-programmed instructions, while in manual mode, operators can make real-time adjustments based on the guidance system feedback.

　　By using this combination of tools, TBMs can follow complex underground paths with precision.

　　Steering a Tunnel Boring Machine is a complex task that involves a combination of high-tech systems and human expertise. From initial planning to real-time operation, every aspect must be carefully coordinated to ensure the successful creation of tunnels that meet design specifications and safety standards. Advances in sensor technology and automation continue to improve the precision and efficiency of TBM operations worldwide.