Herrenknecht AG

After advancing about 3.8 kilometers through rock that was at times extremely hard and at times brittle, the miners working on the northern section of the second tube of the Gotthard Road Tunnel reached their first milestone with a Herrenknecht tunnel boring machine: On April 29, 2026, they celebrated the precise breakthrough into the previously excavated section of the northern fault zone. From here, they will tackle another approximately 4 kilometers of tunnel construction under the Alps heading south.

“Up to 32 meters a day – that’s a remarkable achievement by the tunneling crews in the extremely hard Gotthard rock.” Dr.-Ing. E.h. Martin Herrenknecht, CEO of Herrenknecht AG, is proud of how well tunnel construction for the second tube of the Gotthard Road Tunnel is progressing with the tunnel boring machine (TBM) from Schwanau.

The “secondo tubo” consortium, consisting of partners Implenia and Frutiger, began tunnelling in February 2025 in Göschenen in the Swiss canton of Uri on behalf of the client, the Federal Roads Office (ASTRA). On behalf of the Federal Roads Office (ASTRA), the tunnel construction specialists are excavating the northern section of the new second tube parallel to the road tunnel that has been in operation since 1980. To this end, Herrenknecht engineers designed and delivered on schedule a Single Shield TBM (diameter 12,225 mm) specialized for hard rock.

With the power of seven Formula 1 cars through the underground

The cutterhead of the machine, christened “Alessandra,” is driven by 15 motors with a total output of 5,250 kilowatts – which is roughly seven times the power of a current Formula 1 race car. The hydraulic thrust cylinders press the rotating Cutterhead against the rock face with up to 95,000 kilonewtons – equivalent to the weight of the Eiffel Tower in Paris.

The target of the first tunnelling stage – the northern fault zone – had been excavated conventionally in advance. For this approximately 400-meter-long tunnel section, planners had predicted geological conditions in which mechanized tunnelling would not have been feasible efficiently. After the breakthrough, the tunnel builders will transport the machine – which is about 100 meters long in total – through this cavern before tackling the remaining approximately 4 kilometers to the south. In the coming weeks, the cavern will also serve to thoroughly overhaul the Herrenknecht machine after it has navigated most challenging rock formations to date.

In addition to the sections where the miners were able to achieve peak performance with the TBM, there were stretches with zones rich in quartz or hard, blocky granite that pushed both man and machine to their absolute limits. Johannes Faißt, Herrenknecht project manager for the Gotthard Road Tunnel, explains: “So-called disk cutters are mounted in the rotating cutterhead. As the cutterhead rotates, the disk cutters break up the rock. Depending on the geology, they are subject to specific wear and must be replaced regularly. Here, we were able to provide crucial support for the tunnelling operation with high-quality disk cutters from our Schwanau plant and a logistics process that was closely coordinated with our customer.”

Working toward the northern construction section, a tunnelling operation coming from the south is advancing for the second tube of the Gotthard Road Tunnel. Here, the tunnel boring machine manufactured by Herrenknecht and operated by specialists from Marti AG had been brought to a controlled stop to excavate a defined tunnel length using conventional methods. This demanding work is now largely complete, so that mechanized tunnelling toward the north can resume in mid-May.

From 2003 to 2011, construction consortia at the Gotthard used four Herrenknecht machines to excavate a total of 85 kilometers of tunnel for what was then the world’s longest railway tunnel. The delivery for the Gotthard Base Tunnel ranks among the outstanding milestones in Herrenknecht’s corporate history. This is also confirmed by Matthias Schwärzel, the project management director in charge, for whom it means a great deal to be working with Herrenknecht technology on the Gotthard again: “Tunnel construction in the Alps, and especially at the Swiss St. Gotthard, has always had an emotional component for us.”

Further information:
Herrenknecht AG
www.herrenknecht.com

On the occasion of the successful breakthrough on February 2, 2026, Panama’s President José Raúl Mulino praised the outstanding performance of the tunnel construction team: “I congratulate all of you who made this challenging expedition under the canal possible.” The approximately 4.5-kilometer tunnel is the key structure of the new Metro Line 3, which will connect the western suburbs and downtown Panama City. Until now, 150,000 people commute across a bridge to and from work every morning and evening. The 25-kilometer journey currently takes up to several hours in constant traffic jams. César Pinzón, Director of Metro Panama, referred to this during the ceremony at Balboa station: “For thousands of residents, this first section is a concrete sign that the promised future is approaching, with fast and safe mobility.”

The construction of Metro Line 3 is a premiere: for the first time, a tunnel boring machine is crossing under the Panama Canal, one of the world’s most heavily used and therefore most important waterways. The specifications are correspondingly strict, stipulating that the tunnel construction must not compromise the operational safety of the Panama Canal at any time. In view of the complex geology with high groundwater pressure over 60 meters below sea level, the contracted Consortium HPH with the companies Hyundai Engineering & Construction, Posco Engineering & Construction and Hyundai Engineering opted for a Herrenknecht machine of the Mixshield type. In order to be able to run the metro through the tunnel on two tracks, a correspondingly large tunnel diameter was planned – with a TBM diameter of 13.5 meters. This makes it the largest machine of its kind in Latin America.

The Mixshield machine type developed by Herrenknecht is designed to safely and efficiently handle complex ground conditions and high groundwater pressure. In close cooperation with the customer’s specialists, Herrenknecht engineers equipped the machine with an accessible cutting wheel for the underpass of the Panama Canal: the cutting tools at the front of the cutting wheel can be changed from the rear under atmospheric pressure.

Francisco Avila is the CEO of the Herrenknecht national company in Panama. He is impressed by how the diverse equipment and services from the Herrenknecht Group interlock and optimize the entire tunnel construction process: “In the end, it was a large package that we offered and put together specifically to meet the customer’s requirements. For example: formwork for the segments to line the bored tunnel, a separation plant for processing the excavated soil, three multi-service vehicles for tunnel and construction site logistics, and systems for precise navigation of the huge machine.”

The customer also uses the Herrenknecht.Connected digital platform. Jürgen Hoss, Head of Project Management at Herrenknecht, is convinced: “The TBM alone is equipped with over 4,500 sensors. Keeping track of their data and using them to control processes is a challenge. The tools and dashboards from Herrenknecht.Connected are the solution. This gives everyone involved in the project access to real-time data from the ongoing tunnelling – from the client and partners in the international joint venture to our team in Germany.”

Since tunnelling began in September 2024 on the western shore of the Panama Canal, the teams have been steering the large machine safely and with ever-increasing performance toward its destination. They mastered the critical crossing under the Panama Canal without any problematic incidents. In October 2025, they achieved their peak performance to date of 150 segment rings or 300 meters per month. After breaking through to the future Balboa station east of the Panama Canal on February 2, 2026, Herrenknecht specialists are now helping the Consortium HPH team get the XXL TBM ready for the last stage of about 1.5 kilometers to the final breakthrough.

Further information:
Herrenknecht AG
www.herrenknecht.com

Milestone for a strategic railway project: in late June, the last of two Herrenknecht Single Shield TBMs successfully completed its drive for the new railway line between Rishikesh and Karnaprayag in the Indian Himalayas. The first machine had already reached its destination in mid-April. Now both parallel tubes of the more than 20-kilometer-long tunnel system are complete.

The young Himalayas were long considered virtually unconquerable for tunnelling. Only a few projects in the region’s complex geology have been crowned with success to date. This makes the breakthrough of the second Herrenknecht machine in late June even more significant, after the first TBM had already reached its destination in mid-April. Once completed, the new railway line between Rishikesh and Karnaprayag will reduce the journey time from seven hours to just over two. This represents significant improvements for the region, which serves as an important starting point for Hindu pilgrimages to the sacred Char Dham shrines. Every year, millions of pilgrims take the arduous route along winding roads through deep gorges, which are frequently blocked by landslides and rockfalls in the seismically active zone.

Pioneering work in the Himalayas
The project owner, Rail Vikas Nigam Limited (RVNL), awarded the contract for the line’s centerpiece — a 10.5-kilometer-long twin-tube tunnel — to civil contractor Larsen & Toubro Limited (L&T).

“Indian miners have extensive experience in conventional tunnelling. For a long time, mechanized tunnelling technology was hence viewed by them with skepticism,” explains Sumit Gaur, Herrenknecht’s project manager on site. This skepticism had historical reasons: until now, machine technology has had too few successes in the Himalayas. This project was to change that. L&T therefore opted for two Herrenknecht Single Shield TBMs with a diameter of 9,110 millimeters, designed to meet the challenges of Himalayan geology.

Complex geology calls for innovative solutions
The biggest challenge was the predominant rock type: phyllite. L&T Project Leader & Tunnel expert Chris Cooper explains: “Phyllite is soft but stable. It disintegrates with water. Too much pressure and it clumps together and blocks the cutterhead. That doesn’t exactly make the drive easy.”

To make matters worse, the young, active rock mass is still moving. This can result in subsidence, causing rock to be deposited on the shield skin of the machine and block its progress. To prevent this, the crew can use so-called torque box cylinders. They were integrated into the cutterhead design. “It’s the first time we’ve had this system on a machine in India,” says Sumit Gaur. These allow infinitely variable horizontal and vertical adjustment of the main drive and can increase the excavation diameter by up to 100 millimeters if necessary.

High-tech configuration for extreme conditions
In addition to the innovative torque box technology, the TBMs are equipped with the Herrenknecht ISP system. This sends a surface wave along the tunnel wall, which turns into a spatial wave at the tunnel face. The system records the measurement and excavation data obtained during tunnelling in real time and translates it into a geology report. In an anomaly is detected, additional probe drilling is carried out to check the suspected fault zone. This contributes to safety and a smooth drive. “This is a great advantage for our customers and, of course, especially for our colleagues on the machine,” emphasizes Sumit Gaur. Additionally, a convergence measurement system continuously analyzes the distance between the shield and the rock. If the rock is getting too close to the machine, the machine operator is shown a limit signal.

Impressive advance rates

The comprehensive range of equipment installed on the machine paid off. In record time, 23 rings were installed in just 24 hours. Consequently, at peak times one of the machines advanced a good 39 meters in a day. “That’s impressive, especially in this rock and with this large diameter,” comments Cooper. Fast is also the transport of spare and wear parts. L&T Project Director Rakesh Arora says: “Herrenknecht has its own purpose-built warehouse less than three hours from here in Dehradun and can therefore easily supply new parts when needed. This gives us the flexibility we need.”

With the successful completion of both tunnel drives, the experts have proven that modern tunnel boring machines can also cope with the extreme conditions of the Himalayas. “Here we’ve shown we can move faster with the technology used here than  with  conventional  drill  &  blast,”  emphasizes  Cooper.  The  project  provides important references for subsequent tunnelling projects in this geologically complex region.

Further information:
Herrenknecht AG
www.herrenknecht.com

The so-called Terra Invader systems can penetrate up to 8000 m into the earth in order to tap oil, gas or geothermal resources (Figure 1). The latter are becoming more and more important in times of increasingly scarce fossil resources. This is down to their high availability: there are huge amounts of geothermal energy around the world.

The market leader for tunnel boring machines, Herrenknecht, Schwanau/Germany, entered the deep drilling rig business in 2005. The first systems worked in Germany and Brazil, but the systems are now in operation in many countries around the world. The vertical drilling rigs are developed and manufactured by the subsidiary company Herrenknecht Vertical – and these are made individually for each customer.

When manufacturing the systems, the company works according to the high standards of offshore technology, because the systems are also used offshore. In addition, the systems have a large number of new developments, including an optimised safety concept (hands-off technology). Further features of the state-of-the-art drilling rigs are flexible energy management and integrated noise protection measures. The main advantage of Herrenknecht deep drilling rigs compared to conventional systems, however, is their high degree of automation. This means that users can operate the systems with just four men per shift, which results in significant cost savings.

When designing the drilling rigs, Herrenknecht attaches great importance to optimum explosion protection. The reason for this is that the deep drilling rigs can also tap oil and gas reserves. Their components must therefore be absolutely explosion-proof. The search for a suitable rotary encoder for positioning the top drive and the elevator was difficult under these conditions.

“Very few suppliers have explosion-proof rotary encoders in their product range,” says Jürgen Binder, Herrenknecht Vertical’s technical director. They finally found what they were looking for at the automation technology specialist Hengstler GmbH, Aldingen/Germany.

The ACURO AX71 absolute encoder not only meets the high standards in terms of explosion protection (Figure 2). “Of all the rotary encoders tested, it did the best in terms of field suitability,” recalls Binder. Among other things, the ACURO AX71 impressed with its very good EMC and lightning protection, but also withstood temperatures from –40 to +50 °C and contact with salt water best. It was therefore decided that the absolute optical angle encoder will be installed in all Herrenknecht deep drilling rigs with immediate effect.

The task of the ACURO AX71 on the system is to accurately position the top drive and the elevator, the so-called rack and pinion. Since new drill rods are always being connected, the height position at the elevator must be precisely recorded and added up in order to determine the exact chisel depth. The ACURO AX71 from Hengstler is recommended in every respect for this task, because it outputs binary-coded position values and shows the axis position in relation to a reference point. The rotary encoder is not only distinguished due to its resolutions of up to 12 bit in the multiturn and up to 22 bit in the single turn version. With a diameter of only 70 mm and a shaft diameter of only 10 mm (solid shaft), it is also very compact. The numerous interfaces such as SSI/BiSS and SSI (programmable) as well as Profibus, CANopen and DeviceNet ensure comprehensive compatibility of the rotary encoders.

Hengstler developed the rotary encoder with a stainless steel housing specifically for use in potentially explosive areas in accordance with the ATEX and IECEx guidelines (EN 60079). The ACURO AX71 is therefore suitable for the ATEX zones Ex II 2 G Ex d IIC T4 Gb or Ex II 2 D Ex tb IIIC T135°C Db IP6X. Such zones are found, e. g., in painting, filling, mixing or silo systems as well as in the petrochemical industry or in mills.

The ACURO AX71 was also individually adapted for Herrenknecht. The rotary encoder received a scaling, also called residual value calculation or a rotary indexing function. This ensures that the encoder is reset to zero after a certain number of rotations. The residual value is saved and is available again immediately after switching on the encoder.

Herrenknecht has been using the Hengst-ler rotary encoders successfully for over ten years and will also be installing them on a new geothermal system that is currently being designed. “We are very interested in the new ACURO AX73,” says Binder. This is not surprising. The housing of the pressure-resistant encapsulated rotary encoder, in which the user can easily install their own cable using sophisticated locking technology, would even withstand an explosion on the inside. Any sparks that may occur are also extinguished before they can get outside.

Further information:
Hengstler GmbH
www.hengstler.com
Herrenknecht Vertical
www.herrenknecht-vertical.com