Current and future developments; Insight from two of the world’s leading TBM manufacturers

A number of factors and influences including environmental and societal changes have increased the demand for more tunnels in cities around the world. There are many large-scale transit and water tunneling projects currently underway and more are on the horizon.

Tunnel boring machines (TBM) are the primary means of building the tunnels. The editors of T&UC reached out to two of the world’s largest manufacturers of TBMs, Herrenknect and Robbins, to get insight into the future developments in the industry.

The following is the response from each company. Steffen Dubé, president and general manager of Herrenknecht Tunnelling Systems USA Inc. and Jack Brockway, consultant, former president and general manager of Herrenknecht Tunnelling Systems USA Inc. spoke on behalf of Herrenknect.

Robbins was represented by Doug Harding, Robbins vice president, and Brad Grothen, Robbins technical director.

T&UC: Society has embraced the idea of underground infrastructure in modernizing and developing towns and cities across the world. Globally there is currently a significant demand for new TBMs that seems to be increasing well into the future. How do you see the few premier TBM manufacturers meeting this challenge?

Herrenknecht: Even with a further increase of the demand, based on the current market situation, we would not spot manufacturing capacity issues. Herrenknecht sees itself as a recognized, trusted partner for contractors in mechanized tunnel and pipeline construction in the United States. With our innovative machines we are involved in very complex infrastructure projects and customer-oriented services. We regularly find that our project partners greatly appreciate targeted and project-specific support of their construction activities. Quality and service are generally highly valued, especially for projects with complex challenges or multilayered parameters. We can count on a top team in the United States that works closely and very successfully with our headquarters in Schwanau, Germany. As a family business, we want to continue to provide lasting impetus to the market well into the future.

Brad Grothen, Robbins: Robbins is looking forward to the new challenges that come with improving our cities and infrastructure in geology. While there are fewer manufacturers, there is not a shortage of manufacturing capacity to meet this demand. As in the past, the biggest challenges for those looking to build tunnels will be making sure that contractors have the necessary skills and that the correct machine is employed to build their tunnel.

Doug Harding, Robbins: We see that there is adequate capacity to manufacture the machines; however, the supply chain for the components has been challenged due to the COVID-19 pandemic. We do see as the vaccine is distributed and the number of positive cases starts to reduce, this will bring back confidence in the supply chain.

T&UC: TBMs have been pushing the envelope on what has previously been attempted for the last several decades. What do you see as the greatest challenges for TBM tunneling in the next five to 10 years?

Brad Grothen, Robbins: There have been significant advances in excavation rates, tool performance and reliability in the past and there will continue to be incremental progress in these areas moving forward. Robbins sees the primary areas for development being associated with the efficiency of machines designed to excavate in the most difficult geology, and their ability to do so in a safe manner in a very cost-competitive environment.

Herrenknecht: In recent decades, diameter, face pressure and variable ground have been the development targets. While such factors will continue to be important drivers for development we expect to see additional ones in digital development, automation, sustainability and of course — as has always been — ensuring the highest safety and quality standards must never be at stake.

Looking at the small diameters the demand for increasingly long drives in smaller diameters leads to new technical solutions to install tunnel systems and pipelines exactly where they are needed without harming the environment while protecting aboveground structures.

Our niche in civil engineering is an engineering business for real specialists and pioneers. It profits from technological innovative strength and the enormous diversity of highly specialized companies. Machine technology and customer-specific services optimized for projects and market requirements are not a series or platform business. Technological progress at Herrenknecht is therefore always carried out in well-balanced steps, backed up by expertise, and in partnership.

Doug Harding, Robbins: The challenges will be for TBMs that can cope with a wide range of geology along the same alignment. Machines need to be able to efficiently operate in varying conditions, high pressure, and faulted and fractured geology and tunnels that are deemed to be gassy.

T&UC: What new features and innovation for TBMs are realistic and how much can future project challenges be met with this technology?

Herrenknecht: Technology trends such as digitalization and remanufacturing for an optimized ecological footprint of the projects as well as the further development of established technologies and methods open up interesting opportunities. A major driver for equipment development might also become a future shortage of skilled personnel willing to work underground.

Innovative infrastructure solutions can become additional drivers — on both a large and a smaller scale: the proven mechanized shaft-sinking technology (VSM), for example, can help relieve the tense inner-city parking situation in many places as property prices continue to rise. On a small footprint, with the U-Park system, there is room for many parking spaces in underground shafts with automatically operated parking towers.

The potential of innovations for future project challenges we also see in mining. Due to the constantly growing demand for ores, it is becoming more and more attractive to extract raw materials underground at increasingly greater depths. Whether and when deposits are profitable also depends on the efficiency of the technology used to extract ore deposits. We have therefore used our expertise in mechanized tunneling to develop innovative machine concepts for a variety of applications in mining to make the construction of underground infrastructure in mines safer and more efficient. For example, the first projects with shaft boring roadheaders (realizing shafts 8 m (26 ft) in diameter) demonstrates the potential: twice as fast and safer.

Doug Harding, Robbins: Developments in technology related to ground prediction along the alignment and ahead of the boring information can be invaluable and allow the TBM to be prepared to minimize risk as the geology changes. We also see the technology of data collection on TBM operations to be valuable to detect early failures or improve efficiency of the tunneling operations. Advances in robotics also have a place to allow remote entry into the muck chamber for cutter inspection and changing, which creates a safer environment for the operating crews.

Brad Grothen, Robbins: In some ways the better question is “how do we make our future projects open to new features and innovation?” Since most projects are bid on lowest price with very risk-averse clients, how do we bring innovation into this market?

T&UC: What areas will further automation and digital development enhance TBM operations?

Brad Grothen, Robbins: Digital development, such as data-collection systems that are installed on the machines, now allow contractors to analyze and identify areas in their operation for further improvements. They also allow the owners to better understand how the tunnel was built and better track how it will perform in the future. Care should be taken that these systems are used to enhance operation and the betterment of the industry and not as a legal tool.

Herrenknecht: In addition to the mentioned factors and areas, the integration of performance-related elements of the jobsite is ongoing. The interlinking of jobsite systems in order to achieve best possible results will continue. For example, the monitoring and reporting system going along with Herrenknecht slurry treatment plants (STP) that are operating today not only provide information for the STP operator, it combines datas of the slurry treatment plant and the tunnel boring machine. With this information, the STP operator is able to react proactively in terms of important changes in the TBM drive and it also enables the TBM crew to react promptly to bentonite or separation matters.

Contractors are currently using virtual simulations for training purposes. This can improve the safety and performance of projects significantly as steep learning curves can often be achieved and errors avoided during the operation of the machine. Herrenknecht supports the development of training centers with know-how, hardware and software. A highlight is the erector simulator. It is a virtual learning system for efficient ring-building training and in consequence for decreasing ring building times during operation (latest version with 3D glasses).

T&UC: Regarding artificial intelligence (AI), what are the biggest advancements in regard to tunneling and underground construction? For example, could this lead to automated operation with a real-time understanding of ground; prediction capability in conjunction with TBM operating parameters and what other areas can be developed?

Brad Grothen, Robbins: There is certainly potential for the application of AI in the tunneling industry and it is already being utilized in areas like prediction of ground behavior, such as squeezing ground. One of the strengths of AI is its ability to form algorithms between variables that are not well understood. To do this it takes a lot of clean data where the right decisions and variables are presented. In the coming years AI will certainly be used as a tool to assist operators in making better decisions, especially in areas that have significant economic impact that make the development of the algorithms a worthwhile investment. An example of this would be the relationship between subsidence monitoring sensors and pressure sensors to more accurately model the geology reaction to the machine’s operating parameters, allowing adjustment in near real time. A fully automated machine utilizing ground prediction is still some time off, but the industry and TBM operations will certainly be benefiting in ever-increasing amounts.

Herrenknecht: Yes, these topics named in the question are the key elements regarding AI in the area of tunneling and underground construction.

T&UC: Are there developments in material technology that will have an impact in the next decade?

Herrenknecht: For the predominant material of a TBM, the steel, we would not expect step changes. However ongoing developments in special materials, for bearings, excavation tools and seals will bring continuous improvements there. New manufacturing methods like 3D printing however could trigger further developments. New developments on the tunnel-lining side may, in reverse, have influence on TBM technology.

Doug Harding, Robbins: This will come, in particular for higher abrasion resistant materials for wear areas on the machine. Advances and developments in chemicals to treat the ground and grout technology to support the ground are also advancing and need to be adapted to TBMs.

T&UC: Will we see a maintenance-free TBM with high TBM availability in the next 10 to 20 years?

Herrenknecht: We expect to see far more industrialized processes on TBMs, though probably not a fully maintenance-free TBM. In addition to the tunneling technology for successful tunneling projects, excellent operational service support is a decisive factor to prevent downtimes on the jobsite and enable optimal advance rates. In the future, web-based digital service solutions will also play an important role for smooth tunnel missions. As part of a digital service platform, Herrenknecht is therefore currently developing an e-maintenance tool and an e-shop for spare and wear parts.

Doug Harding, Robbins: The TBMs themselves have been shown to be very reliable along with the muckhandling systems. What we need to focus on in regard to improvements in tunnel availability should be ground conditioning and monitoring along with logistics throughout the complete operation cycle. This will help to improve the overall availability of the tunneling operations.