By Ashley Karen
Herrenknecht AG begun the bauma 2022 with a highly coveted award and received the bauma’s Innovation Award 2022 in the category “Machine Technology” for the new development of continuous tunnelling. The award was received for the next innovation upgrade in the mechanized production of high-performance tunnel infrastructures in all common soft ground constellations (soft ground formations with and without water-bearing layers).
However, continuous tunnelling, equipped with the latest high-technology, leads to a considerable decrease in construction times for longer tunnel sections. This new development is being used in a high-impact mobility project in Europe.
The founder and CEO of Herrenknecht AG, Dr.-Ing. E.h. Martin Herrenknecht, stated on the occasion of the award ceremony: “Continuous tunnelling is the next significant innovation step in mechanized tunneling. New underground traffic routes have to be built ever faster. Continuous tunnelling gives clients and contractors a decisive time advantage that ultimately benefits the entire project and all partners involved. Railroad, metro and road tunnels can be built and put into operation significantly faster. I am particularly proud of the Innovation Award because the new tunnelling method was developed and put to use in Schwanau by our experienced engineers together with young colleagues.”
This is the third time that the bauma Innovation Award has been awarded to Herrenknecht AG: in 2019, the prize was received for the E-Power Pipe® method for the environmentally friendly laying of underground cables, and in 2013 for Pipe Express®, a semi-open method for laying pipelines.
Mechanized tunnelling with shield machines in soft ground has always been a stop-and-go sequential process so far. Each boring stroke is followed by the ring constructing sequence, so that the boring has to pause and the subsequent driving cycle be only begun once the next segmental ring has been installed completely. The interruptions to tunnel advance in soft ground formations caused by these sequential operations costs time when viewed over longer distances.
In contrast, a continuous tunnelling process in which the machine can continue boring while the lining rings are being installed can contribute to considerable savings in building time. Therefore, Herrenknecht engineers designed a process based on the latest technologies and engineering which is a considerable step forward.
The new continuous tunnelling system, developed by the engineers at the Schwanau tunnelling machine manufacturer, achieves a notable rise in efficiency during tunnel construction. Specifically, in the case of longer tunnel sections, continuously organized tunnelling leads to measurable savings in construction time.
Basic principles of continuous tunnelling
Regarding tunnelling, the innovation smooths the following process sequence: In continuous tunnelling, those thrust cylinders that push the machine forward during advance take over the force share of those cylinders that are retracted for ring building. To guarantee that the machine reliably maintains on course under these conditions the center of thrust resulting from the combined driving forces of the applied thrust cylinders must stay unchanged in its position. At the heart of continuous tunnelling is therefore a powerful computer system and process-specific software programs that can precisely measure the necessary pressures in the thrust cylinders. It guarantees that the machine operator can reliably control the TBM along the specified alignment as before.
Safe control in continuous tunnelling
In continuous advance, the machine operator no longer controls the pressures in the thrust cylinders manually using rotary controls (potentiometers) on the control panel. Therefore, Herrenknecht has developed the Center of Thrust (CoT) system newly, which assists the shield operator to precisely control the machine. It includes a display panel that shows the operator the current position of the center of pressure and on which he chooses the desired position of the center of thrust. The corresponding control of the thrust cylinders is handled by the algorithms in the computer system. In contrast to manual control by potentiometers, the CoT offers the prospect of maintaining the specified alignment more effectively and efficiently. Thus, the CoT system can make a sustainable contribution to the economic efficiency of the building project plus the quality of the underground structure.
Faster thanks to advanced Herrenknecht technology
compared to the previous discontinuous method, with continuous tunnelling, a rise in total tunnelling performance of up to a factor of 1.6 can be achieved. This can lead to a great decrease in building time for long tunnels. The unique feature of Herrenknecht’s solution is that continuous tunnelling can be used on all machine types in soft ground.
The continuous tunnelling method is being used in the vital High Speed 2 project – a new rail connection between London and Birmingham. Herrenknecht introduced continuous tunnelling at bauma 2022 in Munich.
