Among technological innovations from

Herrenknecht recently are its TBM continuous tunnelling system, which won a major award at Bauma, and the work it has underway to develop an automated segment production for concrete tunnel lining rings.

The company says a key outcome of the continuous tunnelling system is saving time in the total excavation and ring building cycle and, consequently, in the larger construction operation and time required on a tunnel project. Computerised system play a bigger role to support TBM operators and tunnelling performance could be increased by up to a factor of 1.6.

At the last Bauma, in Munich, in October 2022, the company received the Innovation Award in the Machine Technology category for its development of the new system. Then, Herrenknecht CEO, Martin Herrenknecht, said: “Continuous tunnelling is the next significant innovation step in mechanised tunnelling.”

Another innovation is for concrete segment manufacture where R&D efforts have been underway over the last few years.

The aim of the R&D is to introduce more automation into the production process, including some use of robots alongside static moulds on production lines, and also integration of artificial intelligence with camerabased observation systems and other sensors.

TBM CONTINUOUS TUNNELLING

Soft ground TBM tunnelling has been based on sequential steps of excavation and then ring building, only one activity able to take place at a time. This is a stop-and-go process, says Herrenknecht – where excavation has to pause and can only resume after the segmental ring had been fully installed. The shield pushes off the edges of the completed ring. And the sequence is repeated.

 “Each excavation stroke is followed by the ring building sequence,” says Herrenknecht. It is stop-and-go, or ‘discontinuous’. A pause.

The continuous tunnelling approach overcomes the pause to enable boring forward while simultaneously building rings. The system has been designed to do so by a different approach to the management of thrust cylinders where computerised controls permit the cylinders to operate individually while ensuring their combined effect has the right total pressure and direction of thrust, and so maintains the correct alignment of the excavation.

The core idea is for the TBM operator to check where the display panel is showing the current centre of pressure, resulting from the combined effects of pressures in each thrust cylinder. On the panel, the operator next selects the desired centre of thrust and the computerised system makes the adjustments across the cylinders.

The ‘Centre of Thrust (CoT)’ system moves operators away from manual adjustments of rotary controls (potentiometers) on the control panel to adjust pressures in the thrust cylinders. Instead, in the new computerised control system, the adjustments are managed by algorithms to maintain the CoT spot selected by the operator.

Removing the necessity of the pause offers opportunity to save total time in each cycle of mechanised tunnelling (total of excavation and ring building) and, consequently, in the larger construction operation. Soft ground tunnels could be built faster – and possibly the entire projects, too, depending on how well, after the civil engineering stage, the follow-on activities proceed, such as installation of railtracks/ roadways, M&E, signalling, lightning, ventilation, power, signage, and more.

Herrenknecht said its continuous tunnelling system is on two variable density slurry TBMs being used to build some of the tunnels for Phase 1 of HS2 rail project, in the UK. Tunnelling is well underway on the Chiltern Tunnel, in Lot C1, where Align JV (Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick) is using the two 10.26m-diameter machines to erect concrete rings of 2m length (7, incl key) and 400mm thickness. The TBMs ‘Florence’ and ‘Cecilia’ were launched in mid-2021.

For its technological work, Herrenknecht previously won accolades twice before at Bauma – for its E-Power Pipe system that supports power cable laying (2019), and for its Pipe Express system (2013) for laying pipelines.

SEGMENT PRODUCTION AUTOMATION

As Herrenknecht notes, more producers are relying on automation tools that have proven their advantages and durability for concrete segment production. Advancing technology as well as there being too few skilled workers, the high cost of labour, the need for higher safety levels, and desire for faster, high quality production from lower cycle times are all among the drivers of the change.

Efforts are focused on three areas of robotic support – hydraulic opening/closing of moulds, then cleaning and oiling them before pours, and then once concrete is cast and still wet to apply a rotating pipe-roller to achieve smooth and accurate surface finish.

Each step saves time in delivery the quality sought. For example, the hydraulically-operated mould can have all covers and side walls open in less than half a minute. The system doesn’t involve use of bolts (reducing maintenance needs, in that respect) but a hydraulic steering block to control pressures and obtain the required spatial dimensions and to tight tolerances.

The rotating pipe roller delivers the required surface density as it transports surplus material to the top of the curved casting, enabling voids to be filled, says Herrenknecht. It adds that the entire finishing process takes less than three minutes and the pipe gets cleaned off with water immediately following the task, to await the next mould arriving on the production line.

Sensors are vital to the automation process, including lasers for dimension measurements to ensure the mould is proper position and it is fully closed prior to concrete pour – or casting will be prevented. Correct positioning of some inserts can also be checked, although installing cast-in EPDM gasket is not likely for automation yet and perhaps a full re-design of the sealing system needs to be investigated.

Optical cameras take high resolution photos before and after the surface finishing work by the rotating pipe, helping to detect small holes/voids which may (depending on project/local standards) require another pass by the pipe.

Sensors mounted of the side of a mould can also support temperature measurement of concrete and assessment of early strength development, which helps with optimising heat energy, the concrete mix design, and also demoulding planning.

Effective data management is a crucial to the automation approach, including receipt of the various sensor measurements as inputs to the AI control system’s algorithms. Gradually, as more data are obtained on the repeated tasks, the AI becomes ‘trained’ to better judge against the quality parameters and then issue commands for further actions, if required.

The manufacturing history of each segment can be held in the data management system.

The majority of production lines have static moulds and therefore, for automation, the robots could travel on linear rails/travelling systems, as would electric overhead cranes (EOT) move around the plant, carrying materials to the necessary points of work activity.

Areas for further R&D work include automated manufacture of segment reinforcement formed as steel bar cages, says Herrenknecht.