________________ Highest precision is required to control and navigate a TBM along the entire route until final breakthrough. To achieve this, reliable navigation systems – mainly from our subsidiary VMT GmbH – are used in all Herrenknecht projects. They determine the exact position and movement tendency of the machine and display the data to all those involved in the project in real time. The machine can be kept on a controlled route along the planned tunnel axis at a constant speed, even under the most difficult visibility conditions and in hardest geologies. State-of-theart information and monitoring systems ensure both precise indication of the drilling direction and optimization of the tunnelling processes through realtime monitoring and process data management.
To-the-millimeter precision in very long tunnels
The navigation systems are tailor-made to meet the specific requirements of each tunnel project. Route geometry, diameter, machine type and cost-effectiveness are the essential criteria when selecting the optimum system. The different navigation systems are based either on tacheometry, laser or gyro technology.
When using a laser theodolite-target system, the photo-sensory target unit is mounted in the shield or on the machine frame of the TBM and its position is accurately determined upon installation. A laser theodolite that is fixed to the tunnel wall continuously controls the position of the target unit and determines the position to the tunnel axis during the entire tunnelling process. The measurement direction is displayed and the horizontal and vertical deviation from the shield axis is derived by a visible laser beam. The hardware delivers reliable results and withstands strong vibrations, even in hard rock.
+ Targeted and precise navigation along the planned tunnel axis including curved drives
+ Identification and control of the current machine position and the movement tendencies of the TBM
+ Increased work safety and automated processes by monitoring systems to control tunnelling operations
Clear direction during pipe jacking
Straight tunnel routes are rather rare, even in tunnels excavated using the pipe jacking method. The geology and topography often requires that curved drives or differences in height must be mastered. The tunnel builders maintain the direction, especially in pipe jacking, using the U.N.S. (Universal Navigation System) modular navigation system developed by Herrenknecht. For straight routes of up to 200 meters, a laser is installed in the launch shaft that holds “visual contact” with the target unit at the rear end of the TBM. Thus, horizontal and vertical deviations from the target values can be identified. The navigation system can be extended using a reference module. To protect against refractions, an additional hydraulic water leveling system determines the vertical deviation for longer, straight drives of up to 400 meters. A north-seeking gyrocompass installed in the TBM, which does not require eye contact to the reference module in the launch shaft, makes it possible to master even longer distances, gradients and curves.
Monitoring for segmental lining and pipe jacking
To improve safety during tunnelling and the quality of the tunnel structure, VMT develops supplementary systems for the supervision and automation of processes. They provide the machine driver with additional information and control parameters during tunnelling. For example, software solutions for the segmental lining calculate the optimum ring formation and monitor ring deformations. This achieves optimum positioning of the segments in the tunnel as well as their stability.
Monitoring systems for pipe jacking supervise bentonite lubrication for longer and curved drives. By measuring the joint gap values, the maximum permissible tunnelling forces can be calculated, thus avoiding damage to jacking pipes.
The terrain and buildings above the route are monitored by sensor systems to identify deformations. These also provide alarm and reporting management to analyze data before damage occurs. All data and displays can be retrieved online with appropriate access data. Thus, all of those involved in the project have access to all relevant information anytime and anywhere.