Year: 2025

Huge Robbins Slurry TBM breaks through in Hiroshima

A hard rock heavyweight crossed the finish line this spring with the successful breakthrough of a Robbins 13.67 m (44.8 ft) Slurry TBM in Hiroshima, Japan. The completion of the 1.4 km (0.9 mi) section of the Hiroshima Expressway Line 5 on April 30 is a landmark achievement in challenging geology, and marks the first time a foreign-made large-diameter Slurry TBM has been used to excavate hard rock in the country.

The 2,400 metric ton (2,650 US ton) Robbins TBM was deployed to excavate beneath Hiroshima’s dense urban landscape for the Obayashi-Taisei-Kosei joint venture. The tunnel connects the city’s urban center with a major national highway network and improves access to Hiroshima Airport.

“While there is little track record of large-diameter hard rock drilling with TBMs in Japan, Robbins’ know-how and on-site support for disc cutters, which have a long track record in hard rock drilling, were excellent. We have been able to obtain great results and technical knowledge for future large-diameter slurry hard rock drilling work,” said Mr. Tetsuya Taniguchi, Deputy Director of Obayashi.

The TBM was specially designed to handle the region’s challenging geology, including granite formations with unconfined compressive strengths (UCS) of up to 130 MPa (19,000 psi). The cutterhead and other components were built to withstand these abrasive rock conditions as well as high water pressure.

The machine’s journey began long before its initial cut. Due to the confined urban site and tight transportation restrictions, the TBM was assembled in sections, with each section being split into manageable weights and sizes. Once at the jobsite, which was only 30 meters (100 feet) wide by 60 meters (200 feet) long, the TBM was reassembled using Onsite First Time Assembly (OFTA)—a process that enabled the team to meet a strict timeline of eight months for machine assembly.

The geology encountered was generally very massive, hard granite—while some fracture zones were expected to appear, crews conducted horizontal boring in front of the face every 50 m (160 ft) and these fracture zones were not found. “In addition, there was a section of low cover directly beneath a residential area, but we were able to pass through it safely by taking the appropriate measures to mitigate environmental impacts such as vibration, noise and ground surface displacement,” said Mr. Taniguchi.

As the team moves closer to bringing the tunnel online, the success of the project proves the effectiveness of Slurry TBMs in challenging hard rock conditions. The completion of the tunnel for the project owner, Hiroshima Expressway Public Corporation, is also a boon to the region, supporting its growing economy and tourist sector.

“From the complex machine launch to breakthrough, we are proud of this tunnel being completed for the city of Hiroshima and congratulate the Obayashi-Taisei-Kosei JV. It will make a huge positive impact for the city,” said Mr. Shinichi Konda, Robbins Chief Engineer.

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Robbins TBMs break through at Delhi Metro DC-07 Project

Robbins proudly announces the successful breakthrough of two 6.65 m diameter Earth Pressure Balance (EPB) TBMs on India’s Delhi Metro Phase IV DC‑07 package, achieving a seamless drive from Airforce Station to Tughlakabad Railway Colony Station via Maa Anandmayee Marg Station.

This milestone reinforces Robbins’ commitment to delivering high-performance TBM solutions for critical urban transit projects across India. “This breakthrough is not just a milestone in tunneling, but a testament to the robustness of Robbins technology and the strong collaboration between our field teams and Afcons. The performance of the PLC systems throughout the DC-07 drives was exceptional, ensuring real-time control and precision even in highly variable ground conditions,” said Laxman Khatri, PLC Expert, Robbins India.

The twin TBM drives totaled 2,469 rings, spanning a combined 3,456.6 m of tunnel. Drive 1 totaled 2,651.6 m between Airforce Station and Maa Anandmayee Marg, while Drive 2 totaled 791 m between Maa Anandmayee Marg and Tughlakabad Railway Colony.

The recent breakthroughs in early June 2025 mark the completion of Robbins’ tunneling scope under the DC‑07 package. The drives successfully passed through densely populated urban sectors with difficult logistics and challenging mixed-ground geology consisting of rock with gravel, sand, silt and clay—all with minimal surface impact.

“From launch to breakthrough, our focus was on delivering precision tunneling with minimal surface disruption and maximum efficiency. Despite complex logistics and mixed ground conditions, both drives were completed on schedule with excellent performance. This success reflects the strength of Robbins machines and the dedication of our field teams,” said Gaurav Singh Bisht, Field Service Manager, Robbins India.

This accomplishment marks another successful chapter in Robbins’ long-standing partnership with owner Delhi Metro Rail Corporation (DMRC) and contractor Afcons Infrastructure Limited, contributing to the transformation of Delhi’s urban mobility infrastructure.

With the tunneling phase for DC-07 now completed, Robbins will continue to assist Afcons Infrastructure Limited during TBM dismantling and removal from the tunnels.

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RETC 2025

Event Name: RETC 2025
Dates: June 8-11
Location: Dallas, TX, USA
Venue: Sheraton Dallas Hotel
Booth No: 701

The Rapid Excavation and Tunneling Conference (RETC) is sponsored by the Society for Mining, Metallurgy & Exploration (SME). The show focuses on developments, technology, trends, and innovations that directly affect the tunneling and underground construction industry through a wide variety of technical presentations. Stop by the Robbins booth #701 to meet with our expert staff and find out the latest about our products and projects. Be sure to check out our technical presentation as well:

Monday June 9
Hard Rock TBMs Session

2:30 – 2:50 PM
The Resurgence of Pumped Power Storage & Small Hydropower: How TBMs and Shaft Boring Machines Can Increase Feasibility
Presented by Brad Grothen, Robbins VP Engineering

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