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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 13.67 m (44.87 ft) diameter Robbins Slurry machine broke through this spring, marking the completion of an excavation through challenging granitic rock at high water pressures.
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.
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.
The Robbins TBMs broke through at Tughlakabad Railway Colony station, marking the successful completion of the DC07 contract for Delhi Metro.
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.
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
Twin Robbins EPBs make milestones near Taj Mahal
On June 21, 2024, crew members celebrated a milestone at India’s Agra Metro Project. A 6.52 m diameter Robbins EPB had completed an intermediate breakthrough into SN Medical College Metro Station. The breakthrough was a significant achievement for the contractor, Afcons Infrastructure – Sam India Consortium, as the machine continues its bore on the 29.40 km Agra Metro Phase 1 project.
The Robbins spoke-type EPB TBM completed a 508 m long bore through soft clay strata in less than three months.
“We want to congratulate Afcons-Sam India on the continued success at Agra Metro. They’ve completed this most recent bore in less than three months in a dense urban setting, which is a great result,” said Robbins President Lok Home. “We are confident in the long life and exceptionally robust design of our TBMs, especially when they are well maintained and properly operated.”
The machine was launched on March 23, and completed the 508 m bore through soft clay strata. The breakthrough is the fourth for the Robbins EPB, nicknamed ‘Yamuna’. Previous breakthroughs included one in close proximity to the Taj Mahal. About 200 m or two soccer fields away from the world-renowned structure, that breakthrough was heavily monitored and tracked by the office of the Prime Minister and many others.
‘Yamuna’ is the first of two 6.52 m Robbins EPBs to reach the SN Medical College Metro Station. It’s twin, nicknamed ‘Ganga’, is currently boring a parallel tunnel. The two spoke-type Robbins EPBs, refurbished and customized for soft ground conditions, were originally launched in February and April of 2023. The condition of the TBMs has been good as they broke through into various intermediate stations, requiring no further refurbishments and brief maintenance periods of 15 to 20 days before they were launched again. The TBMs have required minimal usage of spares and cutters during their bores, and both TBMs have thus far successfully bored within their contractual time frames. The bores thus far have included: Ramleela Maidan to Agra Fort Station (334 m); Agra Fort Station to Shahjahan Gardens Midshaft (175 m); Shahjahan Gardens Midshaft to Taj Mahal Station (1175 m) and finally Agra College to SN Medical College (508 m).
Now, the Robbins TBM ‘Yamuna’ will be moved through the station box of SN Medical College and recommissioned in the direction of Jama Masjid Station, also known as Mankameshwar Mandir Station. It will cover a distance of about 1290 m.
With the completion of the 11th breakthrough, seven more remain: two at Raja ki Mandi, two at Agra College, one at SN Medical College, and two at Jama Masjid (Mankameshwar).
Afcons – Sam India Consortium was awarded the Rs. 1819.79 crore civil construction contract for underground Package AGCC-02 by Uttar Pradesh Metro Rail Corporation (UPMRC) in March 2022, with a 48-month timeline. Twin tunnels link the seven stations at Taj Mahal, Agra Fort, Jama Masjid, SN Medical College, Agra College, Raja Ki Mandi, and RBS College.
The high-profile project is one of many metro railway tunnels underway in the country from Mumbai to Delhi, Bangalore to Chennai. Rajat Jain, Sr. Manager of Sales & Operations at Robbins India, sees it as a trend likely to continue: “India has emerged as a top market for tunneling due to several key factors and trends. These include India’s rapid urbanization and demand for infrastructure development, advances in tunneling technology that have made the process more efficient and safer, and India’s growing economy. Tunnels play a crucial role in developing seamless connectivity across the country, reducing travel time, and enhancing the efficiency of goods movement.”
Long Haul TBM: Use of a Rebuilt Main Beam Machine at the DigIndy Tunnel System in Indianapolis, IN
TBMs can last for decades and be rebuilt project after project with proper maintenance. How successful can rebuilt TBMs be? At the DigIndy Tunnel System in Indianapolis, Indiana, USA, a rebuilt TBM was used to great effect. The 6.2 m diameter Main Beam, originally manufactured in 1980, bored 40+ km of tunnels and set three world records in its size class of 6 to 7 m, including a best month of 1,754 m. In this paper, the authors analyze the TBM rebuild, performance and lessons learned to make recommendations for future projects seeking to use rebuilt TBMs over long distances.
Evaluating TBM Design and Performance, 30 Years Apart: The Lesotho Highlands Water Tunnel, Phase 1 and Phase 2
Two massive tunnel projects 30 years apart: The Lesotho Highlands Water Project (LHWP) is a multi-phased project that has taken place over decades to provide water to the Gauteng region of South Africa and to generate hydroelectricity for Lesotho. Phase I tunneling began in 1992 and utilized multiple Main Beam TBMs to bore long tunnels in basalt and dolerite ground conditions. Phase II, now under construction, consists of 38 km of transfer tunnel to be excavated by both TBM and drill & blast.
This paper details the design for the TBMs to be used on the Phase II tunnel, while comparing the modern-day machines to the history-making Main Beams used in the 1990s. It draws some conclusions and lessons learned about boring in volcanic rock at depth utilizing Main Beam vs. Double Shield TBMs.
Overcoming Mountainous Geology at Nepal's Sunkoshi Marin Project
Learn more about the Sunkoshi Marin Diversion Multipurpose Project (SMDMP) in this in-depth video featuring a record-setting Robbins Double Shield TBM. Find out how the crew were able to bore through mountainous geology at an impressive 1,503.3 m in one month and 72.6 m in one day.
Swift Robbins TBM breaks through 11 Months Early
On May 8 in Nepal’s Sindhuli District a crowd of people attending the breakthrough of a speedy TBM had much to celebrate. The 6.4 m diameter Robbins Double Shield machine had overcome incredibly challenging geology to cross the finish line 11 months ahead of schedule. Nepal’s Sunkoshi Marin Diversion Multipurpose Project (SMDMP), at 13.3 km in length, is one of the longest TBM-driven tunnels through the Himalayan mountain range and is only the second such tunnel to be completed in the country. View the breakthrough video here.
At a breakthrough ceremony attended by Nepal’s Prime Minister Pushpa Kamal Dahal, the crowd celebrated an epic TBM breakthrough 11 months ahead of schedule.
“The overall design of the Robbins TBM is proven, and the equipment’s performance and integrity are excellent. Additionally, its adaptability to the Himalayan geological conditions is very impressive,” said Mr. Liu Fengfan, SMDMP Project Manager for contractor B-2/COVEC (China Overseas Engineering Group Co. Ltd and China Railway No. 2 Engineering Group Co Ltd).
Ground conditions included two major fault zones with challenging and varied geology ranging from highly jointed mudstone, sandstone and conglomerate to quartzite, granite, and more. The tunnel was bored through mostly igneous rock with maximum overburden of 1,320 m.
The TBM and its experienced crew were able to persevere through multiple instances of the shield becoming trapped with bypass tunnels required to free it, including one instance 4 km into tunneling that required 27 days’ worth of work to free the machine from collapsing and squeezing ground. Despite the challenges, the crew were able to more than make up the time with swift advance rates including an impressive 1,503.3 m in one month and 72.6 m in one day, both project records set in March 2024.
The success of the machine, despite adversity, is in part due to its proven design. The refurbished TBM was originally used at a smaller diameter on Nepal’s first TBM-driven tunnel, the Bheri Babai Diversion Multipurpose Project (BBDMP). The design incorporates many of the same components of that original machine, and the process involved final assembly on location at the jobsite. It’s something the contractor sees as a positive: “One of the highlights is that this machine integrates the overall structure of the 5.06 m diameter TBM from the Bheri Babai project. After upgrading to 6.4 m diameter, all new front shield components were not assembled in the factory. Instead, we adopted Onsite First Time Assembly (OFTA). This was very effective, and I find it particularly noteworthy,” said Mr. Jin Haikuan, Deputy Project Manager & TBM Production Manager for B-2/COVEC.
With tunneling complete, the work of providing both power and water can begin. The tunnel is connected to a new 28.6 MW surface powerhouse on the Marin River to alleviate the shortage of power supply in the area. It will also be used for farmland irrigation in the districts of Dhanusha, Mahottari, Sarlahi, Rauthat and Bara in the Terai Plain, diverting water from the Sunkoshi River to the Marin River for the project owner, the Department of Water Resources and Irrigation under Nepal’s Ministry of Energy, Water Resources & Irrigation.
The project’s successful completion is a triumph not only for the communities benefiting, but also for the future of tunneling in Nepal. “B-2/COVEC and Robbins have successfully introduced and spread TBM technology in Nepal and shown the advantages of it. This country needs more tunnels,” said Robbins President Lok Home at the breakthrough ceremony. “To have these good performances on these first two projects is really a good thing for the country and our industry.”
NAT 2024
Event Name: North American Tunneling Conference (NAT)
Dates: June 23-26, 2024
Location: Nashville, Tennessee, USA
Venue: Gaylord Opryland Resort & Convention Center
Booth: 901
Come join us in Nashville, TN June 23-26 at the North American Tunneling Conference, the premier tunneling event focusing on current projects, challenges, and successes in tunneling. Stop by our booth 901 to learn more about our ongoing and successful tunneling projects, and be sure to check out our insightful technical presentation.
Technical Presentation
Monday June 24
TBM Technology Session
Presidential Chamber A
11:25 – 11:45 AM
Long Haul TBM: Use of a Rebuilt Main Beam Machine at the DigIndy Tunnel System in Indianapolis, IN
Presented by Doug Harding, Vice President, Robbins & Christian Heinz, Tunneling Division Project Manager, J.F. Shea Construction
World Tunnel Congress 2025
Event Name: ITA-AITES World Tunnel Congress
Dates: May 9-15, 2025
Location: Stockholm, Sweden
Venue: Stockholmsmässan
Stand: B04:10
Come join us May 9-15 in Stockholm, Sweden for the ITA-AITES World Tunnel Congress, the premiere event for tunneling and underground construction. More than 2,000 professionals are set to take part in the world’s top-attended tunneling conference, where hundreds of technical papers will be presented on the latest topics of interest. Stop by our stand B04:10 to converse with our expert international team, and find out the latest about our products and projects.