All advantages at a glance:
Safe tunnelling with precise process and control technology
Exact navigation along the planned tunnel axis including curved drives
Identification and control of the current machine position and the movement tendencies of the TBM
Visualization and data storage of all relevant tunnelling parameters for later documentation
Reliably on track underground
Controlling and navigating a TBM requires the utmost precision along the entire route until the final breakthrough. For this reason all Herrenknecht projects use reliable navigation systems from our subsidiary VMT. They determine the exact position and movement tendency of the machine and display it to all relevant project participants in real time. With state-of-the-art process and control technology, the TBM driver in the control cabin keeps track of the situation while tunnelling is in progess. From here he operates the steering cylinders and maneuvers the machine with absolute precision and control along the planned tunnel axis through the underground, even on the most difficult alignments and in the most challenging geologies.
The equipment used depends heavily on the customer's requirements. Sensors and measuring devices record relevant tunnelling parameters, such as speed, the torque of the drive, the contact pressure of the cutting wheel or the support pressure in the excavation chamber. Computer-aided applications compare the measured values with the targets. In the event of exceeded tolerances, warnings appear to prevent settlement and heaving and the TBM driver can intervene. For non-accessible tunnels and projects in the smaller diameter range, due to the limited space available in the machine the control container is decoupled from the TBM via a bus system and placed at the launch shaft.
Millimeter precision in kilometer long tunnels
For every tunnel project, the navigation systems are individually adapted to the specific requirements. Alignment geometry, diameter, machine type and economic aspects are the key criteria for optimal selection. 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.
Clear orientation 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 increase safety during tunnelling and improve the quality of the tunnel structure, VMT develops complementary systems for monitoring and automating process sequences. They provide the machine driver with additional information and control parameters during tunnel advance.
For example, software solutions for segmental lining calculate the optimal ring sequence and monitor ring deformation. Thus the best possible positioning of the segments in the tunnel and therefore its stability are achieved. Monitoring systems for pipe jacking supervise bentonite lubrication for longer and more curved drives. By measuring joint gap values, maximum permissible thrust forces can be calculated, thereby preventing damage to the jacking pipes. Sensor systems monitor terrain and buildings above the alignment for signs of deformation and provide alarm and reporting management for data analysis before any damage occurs.
All data and visualizations can be retrieved online with appropriate access data. This means everyone involved in the project has access anytime and anywhere to all relevant information (To process data management).
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