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Author: Robbins
Overcoming Multiple Caverns: Successful TBM Tunneling in Karst Geology at Galerie des Janots
In April 2019, a 3.5 m diameter open-type, Main Beam TBM and its crew broke through at the Galerie des Janots Tunnel in La Ciotat, France after encountering two large, uncharted caverns. The 2.8 km long tunnel, excavated in limestone known to have groundwater, karstic features, and voids, took two years to complete due to the challenges encountered. Limestone and powdery clays made for slow going early on in tunneling, until a cavern measuring 8,000 cubic meters in size was encountered on the TBMs left side at the 1,035 m mark. The crew had to erect a 4 m high wall of concrete so the TBM would have something to grip against—a process that took about two weeks. The first cavern, while the largest, was not the most difficult void encountered. At the 2,157 m mark, crews encountered a 4,500 cubic meter cavity extending directly below the bore path. This cavern required stabilization, filling, six bypass galleries, and four months of work to get through.
Robbins Single Shield breaks through Turkey’s Hardest Rock
On July 24, 2020, a jubilant ceremony marked a milestone for southern Turkey’s arduous Bahçe-Nurdaği High-Speed Railway Tunnel. The first TBM-driven portion of tunneling using an 8.0 m (26.2 ft) diameter Robbins Single Shield machine is now complete. The 8.9 km (5.5 mi) long TBM tunnel was no easy bore, as it was excavated through some of the hardest and most abrasive rock ever encountered in the country.
“We are proud of the TBM crew who acted rapidly and were well organized to overcome the challenging ground conditions with a unique Single Shield TBM for the completion of the first tube of the Bahçe-Nurdağı Railway Project,” said Deniz Sahin, TBM Chief for contractor Intekar Yapi A.Ş.
Ground conditions during tunneling ranged from abrasive, interbedded sandstone and mudstone with quartzite veins to highly weathered shale and dolomitic limestone. The TBM encountered rock measuring between 136 and 327 MPa (19,700 to 47,400 psi) UCS. Water ingress with fines was expected in fault lines and shear zones affected by the East Anatolian Fault. “The TBM became stuck in three different fault zones, which we got through by building bypass tunnels. In smaller fault zones, we encountered excessive material flow and the TBM had to be stopped, while ground had to be stabilized with chemical injections while we cleaned the cutterhead,” said Sahin. Water inflows of 10 liters per second on average were removed using a dewatering system.
The majority of tunneling, said Sahin, was in metasandstone with quartz, with an average of 220 MPa (31,900 psi) UCS and a Cerchar abrasion value of 3.87. In such regions, the TBM’s 19-inch back-loading disc cutters had to be changed frequently and there was high vibration. Despite the challenges, Sahin was impressed by the machine’s overall capacity: “The Robbins Single Shield TBM’s motor power, hydraulic power and cutterhead torque were quite strong. The secondary ventilation and air suction systems inside the TBM were powerful. The connections between the gantries, scaffolding systems, walkways and working areas were good.”
The TBM ultimately achieved up to 456 m (1,500 ft) per month, a result achieved with the help of a Robbins continuous conveyor system for muck removal. “The electric motor and gearbox capacity of the conveyor system was quite enough for a 10 km (6.2 mi) tunnel and we had no failure on them. The conveyor performed well even under excess material and the whole system was quite robust,” said Sahin.
The owner, Turkish State Railways Directorate (TCDD), is aiming to overhaul the railway connection in southeastern Turkey by providing a shorter, faster route in one of the country’s busiest railway corridors. The new rail line between the towns of Bahçe and Nurdağı includes two parallel 9.8 km (6.1 mi) tunnels being excavated by both NATM (850 m / 0.5 mi) and TBM (8.9 km / 5.5 mi).
High-Speed Tunneling in the Himalayas: Over 1,200 Meters a Month at Bheri Babai
Nepal’s first TBM-driven tunnel was a success by any standard: The Robbins Double Shield machine bored up to 1,200 meters a month and finished the Bheri Babai Diversion Multipurpose Project nearly a year early. Listen in on our conversation with Brad Grothen P.E., Robbins Technical Director, and Missy Isaman P.E., Robbins Project Engineer, as we discuss the challenges, lessons learned, and recommendations for future tunnels in mountainous geology.
BTS Conference
Event Name: BTS Conference
Dates: March 2-3, 2021
Location: London, UK
Stand: B26
Come visit Robbins at the BTS Conference & Exhibition in London, stand B26 and hear relevant talks on industry hot topics while getting expert advice and information from our team of experienced staff. Check back here for updates as the conference date approaches.
Over 1,200 Meters per Month in Himalayan Geology
Nepal’s first TBM-driven tunnel was a success by any standard: The Robbins Double Shield machine bored up to 1,200 meters a month and finished the Bheri Babai Diversion Multipurpose Project nearly a year early. But how were crews able to bore so quickly? And what made the contractor and owner ultimately decide to use a TBM for the first time?
Watch our complimentary 30-minute webinar with Brad Grothen P.E., Robbins Technical Director, and Missy Isaman P.E., Robbins Project Engineer, as we discuss the challenges, lessons learned, and recommendations for future tunnels in mountainous geology.
Watch the Recording
Bauma CONEXPO India
Event Name: Bauma CONEXPO India
Dates: April 20-23, 2021
Location: New Delhi, India
Come visit Robbins at Bauma CONEXPO India in New Delhi to get expert advice and information from our team of experienced staff. Stay tuned for more information on what you can expect to see from Robbins at the show.
TBMs For Norwegian Small Hydropower Projects
Small hydroelectric projects, with installed capacity up to 10 megawatts (MW), are a relatively untapped but potentially game-changing source of renewable energy in North America. In Norway, hydro projects are pioneering the use of small diameter TBMs in hard rock. Compared with drill and blast, TBMs offer increased production rates and reduction in cross section, among other benefits. The uniquely designed machines are engineered to take on steep gradients, up to a 45-degree angle in some cases.
Completing Mexico City’s Mixed Ground Mega Tunnel: Emisor Oriente
On May 23, 2019, the last of six 8.93 m diameter EPBs completed excavation at Mexico City’s Túnel Emisor Oriente (TEO), a feat marking the completion of ten years and 62.1 km of tunneling. The TEO is a critically-designated plan to stem severe flooding while boosting wastewater capacity, and is the country’s largest infrastructure project. The six EPB TBMs excavated some of the most complex geology on earth, ranging from abrasive volcanic rock to watery clays.
Project Clear: Efficient Hard Rock Tunneling below St. Louis, Missouri
The Metropolitan St. Louis Water District’s Project Clear is a 28-year program targeting water quality and wastewater capacity throughout St. Louis, MO. The extensive program involves multiple tunnels, including Deer Creek, a 6.3 km long tunnel being bored with the largest TBM ever used in the St. Louis area (6.5 m in diameter). Another tunnel, Jefferson Barracks, is using TBM components that have bored over 40 km of tunnel since 1981.
Cutting Edge Virtual Event
Event Name: Cutting Edge Conference
Dates: November 10-11, 2020
Location: Dallas, Texas, USA
Come visit Robbins at the Cutting Edge Conference, now a virtual event, and hear relevant talks on industry hot topics. Learn more about the largest hard rock TBM ever to operate in the USA at the Mill Creek Project. The 11.6 m (38.1 ft) diameter Robbins Main Beam TBM is excavating an 8 km (5 mi) long tunnel in Dallas.
Tune in during the technical sessions as well to find out the latest on tunnel boring machinery for mines, presented by Robbins Chief Engineer Dennis Ofiara:
Tuesday November 10, Session 2 – Innovation in Tunneling
| 1:30 pm MST | The Future of Tunnel Boring for Underground Mines Dennis Ofiara, The Robbins Company |