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In December 2019, the City of Dallas, Texas, USA unveiled the largest hard rock TBM ever to bore in the U.S. The 11.6 m (38.1 ft) diameter Robbins Main Beam TBM will excavate the 8 km (5 mi) Mill Creek Drainage Relief tunnel, and its size is not its only distinction. The adaptable machine will change size partway through the bore, to a more compact 9.9 m (32.5 ft).
The unique Robbins TBM will be used to dig a tunnel designed to provide 100-year flood protection for east and southeast Dallas, areas affected in recent years by severe storms. The tunnel will protect 2,200 commercial and residential properties, including Baylor Medical Center. The current drainage system in these areas was constructed 50 to 70 years ago, and only provides two to five years of flood protection. “The completion of the TBM assembly marks a major milestone in the Mill Creek Tunnel Project,” said Council Member Lee Kleinman, chair of the Transportation and Infrastructure Committee for the City of Dallas. “I’m thrilled to see this type of engineering marvel happening right here in Dallas.”
The dual-diameter aspect of the Robbins TBM will be a first-of-its-kind conversion process. The contractor, Southland/Mole Joint Venture (SMJV), will make the conversion underground about 2.8 km (1.8 mi) into the bore. The two diameters are needed as the upstream section of the tunnel is designed with a circular cross section and peak flow rate of 42 m3/sec (15,000 ft3/sec), while the downstream 2.8 km (1.8 mi) portion has a higher peak flow of 565 m3/sec (20,000 ft3/sec) and was initially designed as a horseshoe cross section. Using the TBM for the entire tunnel is less time consuming and costly. “Robbins and SMJV are working closely to create the safest and most efficient sequence for completing this conversion within the limits of the bore. The City of Dallas (Owner) and our Project Team are very excited to embark on this unique challenge,” said Nick Jencopale, Project Manager for Southland Holdings.
The Robbins TBM, named “Big Tex” with permission of the State Fair of Texas, has been designed with a specialized cutterhead including removable spacers and adjustable bucket lips to convert to a smaller diameter. The TBM will first complete its 11.6 m (38.1 ft) diameter section of the alignment, then back up about 21 m (75 ft) to a transition area for the conversion, which is expected to take six to eight weeks.
As the TBM bores, it will pass through Austin Chalk between 12 to 30 MPa (1,800 to 4,400 at depths from 31 to 46 m (100 to 150 ft) below the city. The route is potentially gassy, so probe drilling is mandatory throughout the project. Crews will utilize ground support including eight 3.9 m (13 ft) long rock bolts every 1.5m (5 ft) with wire mesh and channel straps as needed. The finished tunnel will be lined with a 380 mm (15 in) thick cast-in-place concrete lining.
“Big Tex will work 24 hours a day to excavate the tunnel with crews ranging in size depending on activities,” said Rachel Sackett, marketing and communications director for Southland Holdings. Based on previous work through similar geology, the project team expects TBM excavation to progress rapidly to an average of 25m (80 ft) per day, allowing the project to be completed on schedule in 2023.
In 1979, a 4.56 m diameter Robbins Double Shield TBM was delivered to bore the Severomuysky Service Tunnel, a 15.3 km long railway through the remote mountains of Siberia. Now, 40 years after the original machine was delivered, Robbins is returning to the role. Two 10.37 m diameter Crossover (XRE) TBMs will bore the second Severomuysky Tunnel, clocking in at 15.5 km long and running through mixed ground and fault zones. The new rail line is needed due to limitations on carrying capacity on the current Baikal-Amur Mainline (BAM) railway through the area. Currently 16 million tonnes of cargo are carried through the existing Severomuysky tunnel but the Russian Government wants to increase cargo carrying capacity by more than six times in the region.
The largest global anthracite producer, Sibanthracite Group, is taking on the tunnel construction with management by VostokCoal Management Company. The companies, owned by Dmitry Bosov, aim to increase coal transport by up to 100 million tonnes per year through the addition of the second tunnel. “Robbins has established itself on the market as the best manufacturer of hard rock machines, which are able to provide the maximum penetration rate in hard rock. This is one of the determining factors in connection with the tight deadlines for the implementation of our project. Also, Robbins is the only manufacturer to build the Crossover TBM,” said a representative of Sibanthracite Group. Other aspects of the supply include a continuous conveyor for muck removal, rolling stock, spare parts, and cutting tools.
Sibanthracite Group chose Crossover technology for a number of reasons, geology being chief among them. “A Crossover type tunnel boring machine was selected for tunneling due to the fact that the construction of the tunnel will be carried out in difficult heterogeneous geological conditions (from unstable waterlogged soils to hard rock). The Crossover is able to operate in two modes: Open mode, used while boring in hard rock formations, and closed mode (with earth pressure balance), used when boring in unstable water-logged soils,” said the Sibanthracite representative.
The lessons learned during the first Severomuysky tunnel—the importance of probe drilling, consolidation grouting, and preventing a shielded machine from becoming stuck in fault zones or squeezing ground—are all part of the Crossover TBM solution. “I was a young engineer working at Robbins when the Double Shield TBM was delivered for the first tunnel, so it is a special honor to bring this new technology to the second Severomuysky Tunnel in Siberia,” said Robbins President Lok Home. “Per the contract Robbins is supplying Crossover TBMs for the new parallel rail tunnel—these machines are made to bore in highly variable ground conditions while maintaining good advance rates. With our latest technology we hope to again prove TBMs are the better choice over Drill and Blast when difficult ground conditions are to be encountered.”
The machines will be designed for varying water pressures, ranging from 5 to 20 bar. They will feature Water Inflow Control, a system that seals off the face and periphery and creates a safe working environment in which to dewater and consolidate ground. The machines will feature probe drill ports and capabilities for 360-degree probe drilling and grouting ahead of the excavation face, while the Robbins Torque-Shift System will enable the machines to bore through collapsing ground and other situations that demand high torque. The machines will also be designed with a belt conveyor in hard rock mode that can be switched out with a screw conveyor when crossing into soft ground.
Crews will bore through the Severomuysky Ridge, a mountain range in Buryatia and part of the Stanovoy Highlands, which separates the basins of the Upper Angara and Muya Rivers. “The second Severomuysky tunnel is located in one of the most geologically active areas of our planet—on the north-eastern flank of the Baikal rift zone. The region is characterized by high seismic activity, difficult geological and hydrogeological conditions against the backdrop of a harsh climate (the summer period lasts only 80-100 days, temperatures from + 39°C in summer to -58°C in winter). The construction work on the portals is complicated by the presence of permafrost as well,” said the Sibanthracite representative. Construction of the new tunnel is expected to begin in 2020 and take five years.
In August 2019, a small diameter Double Shield TBM made a big impact. The 2.46 m (8.07 ft) diameter Robbins machine completed 3,475 m (11,400 ft) of boring with no intermediate access, making it the longest rock tunnel ever bored by a Double Shield TBM under 2.5 m (8.2 ft) in diameter.
The machine completed the Parmer Lane Wastewater Interceptor in Austin, Texas, USA for contractor S.J. Louis Construction. Despite obstacles including two tight curves of 150 m (500 ft) radius and unexpected ground conditions that required modification of the cutterhead in the tunnel, advance rates were good. The machine reached up to 380 m (1,250 ft) per month while mining in single 12-hour shifts per day. “It was a hard rock TBM, and it performed better than expected through hard rock,” said Zach West, Project Manager for S.J. Louis.
The challenges for the TBM and its crew were varied, explained West. “The pairing of this tunnel length, which is on the longer side, and the diameter, which is on the smaller side, is challenging. The survey in a small tunnel with tight radius curves and limited surface access for over two miles is very difficult.” He added that the shallow tunnel depth, and the alignment to within a few feet of sanitary lines, high-pressure gas mains, and fuel tanks for gas stations, made TBM guidance critical. “I would say that I am most proud of our ability to guide the machine successfully through these obstacles and into our retrieval shaft within our expected tolerances.”
Through one stretch, the tunnel advanced directly between a 30 cm (12 in) diameter, high-pressure gas main and fuel tanks for a gas station with limited as-built information. “Navigating this section took a great deal of coordination with the local utility companies. Because the tunnel diameter was too small for an automated guidance system, we manually surveyed the front of the machine at every push to ensure the machine was on track,” said West.
“I’m proud that they mined the longest tunnel to date for a small shielded gripper machine of this size without any safety issues. Kudos to their management philosophy and jobsite team,” said Tom Fuerst, Robbins Utility Tunneling Sales Manager. Robbins assisted the crew while in the tight 150 m (500 ft) curves and helped with modifications required to the cutterhead and disc cutter arrangement.
The tunnel is located in an environmentally sensitive aquifer, with ground conditions ranging from soft dolomite with clay to limestone from 13 to 68 MPa (2,000 to 10,000 psi) UCS. “While we tunneled through the softer material, our best advance rate was close to 0.9 m (3 ft) per hour. When we tunneled through the expected limestone, advance rates were over 5.2 m (17 ft) per hour. Our best day was 25 m (81 ft) in a single shift,” said West.
The majority of the tunnel used a simple two-rock-bolt pattern for support. In the last 10% of the tunnel, ribs and lagging were used as support. Final carrier pipe, which is now being installed, consists of 110 cm (42 in) diameter fiberglass pipe.
The successful project is part of a larger trend towards small diameter, TBM-driven rock tunnels in the United States, says Fuerst. “It is primarily due to demographics and business growth. The parts of the USA that are growing need to build out their sewer and water infrastructure. TBMs can mine long distances with tight curves. They can reduce the need for multiple shafts, which lowers the overall project cost. And, given that most small diameter pipelines follow a road or municipal right-of-way, traffic problems are reduced significantly compared with open cut operations.”
The Parmer Lane Wastewater Interceptor connects to two existing lift stations at Lake Creek and Rattan Creek. The tunnel allows for these lift stations to be decommissioned, and will provide additional flow capacity by gravity, reducing operating costs for the City of Austin.
Adapted from the official press release of the New York City Department of Environmental Protection (NYCDEP).
On Tuesday August 13, The New York City Department of Environmental Protection completed excavation of the Delaware Aqueduct Bypass Tunnel, a significant milestone in the USD $1 billion effort to repair leaks in the longest tunnel in the world. The moment happened at 6:51 a.m. when a tunnel boring machine broke through a wall of shale bedrock nearly 700 feet (210 m) beneath the Town of Wappinger in Dutchess County, New York, USA. Excavation of the tunnel was completed on budget and ahead of schedule.
“I want to congratulate the engineers, project managers and local laborers who steered us toward this milestone with considerable skill and precision,” DEP Commissioner Vincent Sapienza said. “Holing through is a major achievement for any tunneling project, especially one as large and complex as our repair of the Delaware Aqueduct. The moment is also a reminder that much work remains to be done as we move steadily toward completing this project in 2023 and ensuring the long-term reliability of the water supply system that sustains 9.6 million New Yorkers every day.”
The Delaware Aqueduct Bypass Tunnel is the largest repair project in the 177-year history of New York City’s water supply system. Its centerpiece is a 2.5-mile-long bypass tunnel that DEP is building 600 feet (180 m) under the Hudson River from Newburgh to Wappinger. When the project is finished in 2023, the bypass tunnel will be connected to structurally sound portions of the existing Delaware Aqueduct on either side of the Hudson River to convey water around a leaking section of the tunnel. The 85 mile (138 km) long Delaware Aqueduct, the longest tunnel in the world, typically conveys about half of New York City’s drinking water each day from reservoirs in the Catskills.
A massive Single Shield tunnel boring machine, manufactured by The Robbins Company in Solon, Ohio, USA, began to excavate the tunnel on Jan. 8, 2018. The tunneling machine mined 12,448 feet (3,794 m) during the 582 days that it pushed eastward from its starting point nearly 900 feet (270 m) below the surface in the Town of Newburgh in Orange County. According to data tracked by DEP, the machine excavated 89.8 linear feet (27.4 m) on its most productive day, 354.8 feet (108.1 m) during its best week, and 945 feet (288 m) during its most productive month. The tunnel boring machine excavated through three bedrock formations, starting with the Normanskill shale formation on the west side of the Hudson River, the Wappinger Group limestone formation, and finishing in the Mt. Merino shale formation on the east side of the river. The location and condition of these bedrock formations was well documented by New York City when it originally built the Delaware Aqueduct in the 1930s and 1940s. Engineers used that historical information to design the tunnel boring machine for the bypass tunnel and plan for its excavation.
As the tunnel boring machine forged ahead, it also lined the shale and limestone bedrock with precast rings of concrete. A total of 2,488 concrete rings were installed by the machine. Now that mining is finished, DEP will begin to install 16 foot (5 m) diameter steel liners inside the first layer of concrete. After the 230 steel liners are installed and welded together, they will be coated with a second layer of concrete. This “triple-pass” design will provide the bypass tunnel with structural stability and prevent leaks from occurring again in the future. During the excavation, the tunnel boring machine was driven, maintained and supported by dozens of local laborers who worked 24-hours, six days a week. They operated cranes, trucks and underground trains to collect the pulverized rock and haul it to the surface. They removed and replaced cutting discs on the front of the machine, and maintained the many complex systems that kept the tunnel boring machine functioning properly.
The Delaware Aqueduct Bypass Tunnel is the first tunnel built under the Hudson River since 1957, when the south tube of the Lincoln Tunnel was finished.
Background on the Delaware Aqueduct repair project
DEP has monitored two leaking sections of the Delaware Aqueduct – one in Newburgh, and the other in the Ulster County town of Wawarsing – since the early 1990s. The leaks release an estimated 20 million gallons (76 million liters) per day, about 95 percent of that escaping the tunnel through the leak near the Hudson River in Newburgh. DEP has continuously tested and monitored the leaks since 1992. The size of the cracks in the aqueduct and the rate of leakage have remained constant over that time.
In 2010, the City announced a plan to repair the aqueduct by building a bypass tunnel around the leaking section in Newburgh, and also by grouting closed the smaller leaks in Wawarsing. The project began in 2013 with the excavation of two vertical shafts in Newburgh and Wappinger to gain access to the subsurface. These shafts, 845 and 675 feet (258 and 206 m) deep respectively, were completed in 2017. Workers then built a large underground chamber at the bottom of the Newburgh shaft. That chamber has served as the staging area for assembly and operation of the tunnel boring machine, and as the location from which excavated rock is brought to the surface by underground trains and a large crane.
The existing Delaware Aqueduct will stay in service while the bypass tunnel is under construction. Once the bypass tunnel is nearly complete and water supply augmentation and conservation measures are in place, the existing tunnel will be taken out of service and excavation will begin to connect the bypass tunnel to structurally sound portions of the existing aqueduct. While the Delaware Aqueduct is shut down, work crews will also enter the aqueduct in Wawarsing to seal the small leaks there, roughly 35 miles (56 km) northwest of the bypass tunnel.
The project will mark the first time that the Delaware Aqueduct will be drained since 1958. In 2013, DEP installed new pumps inside a shaft at the lowest point of the Delaware Aqueduct to dewater the existing tunnel before it is connected to the new bypass tunnel. Those pumps will be tested several times before the tunnel is drained in 2022. The nine pumps are capable of removing a maximum of 80 million gallons (302 million liters) of water a day from the tunnel—more than quadruple the capacity of the pumps they replaced from the 1940s. The largest of the pumps are three vertical turbine pumps that each measure 23 feet (7 m) tall and weigh 9 US tons (8 metric tons).
Background on the tunnel boring machine “Nora”
The Delaware Aqueduct Bypass Tunnel was excavated by one of the world’s most advanced tunnel boring machines (TBM). The Robbins Single Shield TBM – which measures more than 470 feet (140 m) long and weighs upwards of 2.7 million pounds (1.2 million kg) – was named in honor of Nora Stanton Blatch Deforest Barney, a noted suffragist and the first woman in the United States to earn a college degree in civil engineering. Nora, who worked for the City’s as a draftsperson during the construction of Ashokan Reservoir, was also the first female member of the American Society of Civil Engineers.
The USD $30 million TBM arrived at the site in Newburgh in 2017. It was delivered in 22 pieces and took four months to assemble. The 21.6-foot (6.58 m) diameter TBM was built to withstand more than 30 bar of pressure. The machine needed to withstand high pressure because workers encountered huge inflows of water under immense pressure when the aqueduct was first built more than 70 years ago. The TBM was equipped with pumping equipment to remove up to 2,500 gallons (9,400 liters) of water per minute away from the tunnel as the machine pushed forward. The TBM was also outfitted with equipment to install and grout the concrete lining of the tunnel, and to convey pulverized rock to a system of railroad cars that followed the TBM as it worked. The railroad cars regularly traveled back and forth between the TBM and the bottom of Shaft 5B in Newburgh, delivering workers, equipment and rock between the two locations.
On May 23, 2019, a celebration was in order: The last of six 8.93 m (29.3 ft) diameter EPBs had completed excavation at Lot 4 of Mexico City’s Túnel Emisor Oriente (TEO), a feat marking the completion of ten years and 62.1 km (38.6 mi) of tunneling. “We are proud of having successfully finished the excavation, despite all the adversities we faced, such as large inflows of water, hydraulic loads and constant changes in geology. We solved these by adapting the excavation mode according to each type of geology found,” said Hector Arturo Carrillo, Machinery Manager for Lot 4 contractor Carso Infraestructura y Construcción (CARSO).
Despite multiple challenges, the operation achieved a project record of 30 m (98 ft) in one day, and a high of 528 m (1,732 ft) in one month. It’s a result that, Carillo says, has much to do with the continuous conveyor system being used for muck removal: “It should be noted that our advance rates were achieved thanks to the great Robbins conveyor design. The tunnel conveyor was composed with elements such as the booster, vertical belt, curve idlers, and advancing tail piece, as well as elements on the surface. Personally, I think it is a great, admirable system that has helped us achieve the TBM’s performance.”
The breakthrough was the latest and greatest milestone for an urgently needed wastewater project that spanned some of the most difficult geology ever encountered by EPBs. The 10.2 km (6.3 mi) long Lot 4, running from Shaft 17 to Shaft 13 at depths of up to 85 m (280 ft), included sections of basalt rock interspersed with permeable sands with high water pressure. “Our machines had to go through the worst geology, but they were designed for it,” said Roberto Gonzalez Ramirez, General Manager for Robbins Mexico, of the three Robbins EPBs and continuous conveyor systems used on Lots 3, 4, and 5 of the project.
All of the machines were designed for water pressures from 4 to 6 bars, with mixed ground, back-loading cutterheads to tackle variable ground conditions. High pressure, tungsten carbide knife bits could be interchanged with 17-inch diameter carbide disc cutters depending on the geology. Other features included man locks and material locks designed to withstand pressures up to 7 bar, a redesigned bulkhead, and Hardox plates to reinforce the screw conveyors as well as removable wear plates to further strengthen each screw conveyor flight. The rotary union joint was redesigned to improve cutter change times during cutterhead interventions, while a new scraper design offered more impact resistance in mixed ground conditions with rock.
The Lot 4 TBM was assembled in the launch shaft no. 17 and commissioned in August 2012, with the bridge and all the back-up gantries at the surface. Two months later in October 2012, after advancing 150 m (490 ft), the machine and its back-up were completely assembled in the tunnel. One month later, the continuous conveyor system was installed and running.
After 405 m (1,328 ft) of excavation, the presence of rocks, scrapers, parts of the mixing bars and other wear materials in the excavated muck prompted a cutterhead inspection. With high pressure up to 3.5 bars, it was determined that a hyperbaric intervention was necessary, and on June 2nd, 2013 the first hyperbaric intervention through an EPB in a tunnel was performed in Mexico. However, these interventions were done at great cost and proved to be time-consuming. After about 50 hyperbaric interventions the remainder of the project’s interventions were done in open air. “The interventions carried out in atmospheric mode were the biggest challenge. The great influx of water tested the limits, because we were excavating on a decline. In all of these interventions we had to implement a double pumping system, at both the TBM and the shaft,” said Carrillo. Despite the challenges of pumping water at volumes up to 180 l (48 gal) per second and cleaning fines from the tunnel each time the operation was performed, atmospheric interventions were still lower in cost and quicker than those done at hyperbaric pressure.
Even when conditions were tough, Carrillo felt his operation was well-supported by Robbins Field Service: “Robbins were always present giving ideas and contributing all their experience to solve the problems. One of the most recent examples, almost at the end of this project, was where the machine encountered a blockage to the shield and could not move forward. It became necessary to implement the exceptional pressure hydraulic system, reaching a pressure range of 596 bar on 28 thrust cylinders. Robbins personnel helped us during all that time and we were able to get through it.”
In April 2019, a Robbins Double Shield TBM defied the notoriously difficult geology of the Himalayas to break through about one year ahead of the overall project schedule, and seven months ahead of the TBM tunneling schedule. Nepal’s first tunnel boring machine, at 5.06 m (16.6 ft) diameter, achieved over 1,000 m (3,300 ft) monthly advance on two separate occasions and averaged over 700 m (2,300 ft) per month over the course of tunneling. The machine completed the 12.2 km (7.5 mi) Bheri Babai Diversion Multipurpose Project (BBDMP) for the Government of Nepal’s Department of Irrigation (DOI) and contractor China Overseas Engineering Group Co. Ltd. Nepal Branch (COVEC Nepal).
The large and well-attended ceremony featured a speech by the Prime Minister of Nepal KP Sharma Oli, where he praised the project and its success for the future of TBM projects in the country. “It is not just that new technology has entered Nepal; it is a matter of great gain. The government has plans to execute various other multipurpose projects such as the Sunkoshi-Marin Diversion Project.”
The machine’s completion of the tunnel in just 17 months came nearly a year ahead of the DOI’s deadline for completing the tunnel of March 28, 2020, with the contractor’s schedule being more aggressive. “The breakthrough ceremony was great. We’re proud that we finally did it and were ahead of the overall schedule by almost one year,” said Mr. Hu Tianran, Project Manager for COVEC.
When the BBDMP was fast-tracked as one of the country’s “National Pride Projects” feasibility studies showed that Drill & Blast excavation of the tunnel could take as long as 12 years. The DOI needed a faster option, and they found it in TBMs. They began working with local Robbins representatives MOSH Tunnelling to bring what would be the first Nepalese TBM ever into the country. The process for the DOI to acquire funding for the project and select a contractor through international competitive bidding took seven years, spanning from 2007 to 2015, when project commencement officially began. “We are proud to have introduced TBM technology successfully,” said Prajwal Man Shrestha, Robbins Representative in Nepal with MOSH Tunnelling. “Despite roadblocks and resistance along the way, we eventually introduced this technology, which broke all tunneling records in Nepal. The country has received international attention and contractors and developers from around the world are now considering Nepal for future TBM projects.”
The tunnel is located in the Siwalik Range, part of the Southern Himalayan Mountains, where geology consists of mainly sandstone, mudstone, and conglomerate. “Using the TBM method instead of the conventional drill and blast method was the key factor for the success of this project. It has set a good example for the implementation of a large number of similar tunnels in Nepal’s water/energy/transportation projects in the future. There are promising prospects in the application of TBM technology in Nepal in my point of view,” said Mr. Hu.
To ensure the best TBM performance and to prevent downtime, machine maintenance occurred daily at a fixed time. Geological engineers analyzed the ground conditions twice daily to adjust the tunneling parameters if needed. The careful plan of excavation worked: The knowledgeable COVEC team traversed a risky fault zone, the Bheri Thrust at the 5.8 km (3.6 mi) mark, with no problems, and overcame a stuck TBM shield at another point with a bypass tunnel constructed in just five days. To cope with the conditions, the Robbins machine was designed with Difficult Ground Solutions (DGS), a suite of features including enhanced probe drilling and forepoling capabilities, as well as a stepped machine shield and smooth cutterhead design to avoid becoming stuck in collapsing ground.
The secret to the machine’s rapid excavation is good planning, says Mr. Hu: “As the contractor and the equipment supplier jointly carried out in-depth research and detailed design in the preliminary stage, the TBM was matched to the various conditions of the project. Together with the advantages in hard rock construction that The Robbins Company has, we made an excellent performance of the TBM on this project.”
Once the BBDMP is operational, it will irrigate 51,000 hectares of land in the southern region of Nepal, and provide 48 MW annual generating capacity. It will divert 42 cubic meters (1,500 cubic feet) of water per second from Bheri River to Babai River under a head of 150 m (490 ft) using a 15 m (49 ft) tall dam, providing year-round irrigation in the surrounding Banke and Bardia districts. The estimated annual benefit in Nepalese Rupees is $2.9 billion for irrigation, and $4.3 billion for hydropower, making a total of NPR $7.2 billion (approx. USD $64 million) in benefits once the project becomes active.
In April 2019, a Robbins 3.5 m (11.5 ft) diameter Main Beam TBM broke through into open space, completing its 2.8 km (1.7 mi) long tunnel. It was not the first time the machine had encountered open space: twice during tunneling, the machine hit uncharted caverns, the largest of which measured a staggering 8,000 cubic meters (283,000 cubic ft) in size.
The obstacles overcome at the recent breakthrough are a significant achievement, said Marc Dhiersat, Project Director of the Galerie des Janots tunnel for contractor Eiffage Civil Construction. “We are proud to have led a motivated and conscientious team to the end of the tunnel who worked well without accidents despite the many technical difficulties encountered.”
The water tunnel, located below the community of Cassis, France, is an area of limestone known for its groundwater, karstic cavities, and voids. The limestone, combined with powdery clays, made for difficult excavation after the machine’s March 2017 launch. At the 1,035 m (3,395 ft) mark, the crew hit a cavern on the TBM’s left side. The cavern, studded with stalactites and stalagmites, was grazed by the TBM shield. The crew had to erect a 4 m (13 ft) high wall of concrete so the TBM would have something to grip against. The TBM was then started up and was able to successfully navigate out of the cavern in eight strokes without significant downtime to the operation—the process took about two weeks. Despite the challenges, Dhiersat thought positively of the TBM throughout the ordeal: “This has been the best machine for the job due to all the geological difficulties.”
The first cavern, while the largest, was not the most difficult void encountered. The machine was averaging 20 to 22 m (65 to 72 ft) advance per day in two shifts after clearing the first cavity, with a dedicated night shift for maintenance. While excavating, a combination of probe drilling and geotechnical BEAM investigation—a type of electricity-induced polarization to detect anomalies ahead of the TBM—were used. Crews ran the excavation five days per week, achieving over 400 m (1,310 ft) in one month. This performance continued until the 2,157 m (7,077 ft) mark, when the machine grazed the top of an unknown cavity that extended deep below the tunnel path. The structure measured 22 m (72 ft) long, 15 m (49 ft) wide, and 14 m (46 ft) deep, or about 4,500 cubic meters (159,000 cubic ft) of open space.
Crews probed in front of the cutterhead and began work to stabilize and secure the cavity with foam and concrete, as well as excavate a bypass gallery. “After filling much of the cavity (1,500 m3/53,000 ft3), our biggest difficulty was to ensure the gripping of the machine: We needed six bypass galleries and four months of work to reach the end of this challenge,” said Dhiersat. For the last 600 m (2,000 ft) of tunneling, “we were finally in good rock,” he emphasized. Overall rates for the project averaged 18 m (59 ft) per day in two shifts, and topped out at 25 m (82 ft) in one day.
“The cooperation with Marc and his team on site was very good and we always enjoyed their professionalism and commitment to the project and the task. This, without any doubt was key for the success we achieved,” said Detlef Jordan, Business Manager Robbins Europe. “For us, it was satisfying and motivating to see that, by working together and joining the efforts of all partners on the project, the best and most successful outcome can be achieved. This commitment for decades has been at the heart of success in the tunneling industry, but it has not always been observed on other recent projects.”
Galerie des Janots is one of fourteen operations designed to save water and protect resources, which are being carried out by the Aix-Marseille-Provence metropolis, the water agency Rhône Mediterranean Corsica, and the State Government. The Janots gallery, once online, will replace existing pipelines currently located in a railway tunnel—these original pipes have significant deficiencies with estimated water losses of 500,000 cubic meters (132 million gallons) per year. The new tunnel will increase capacity to 440 liters (116 gallons) per second.
On February 28, 2019 a ceremony was held to mark the breakthrough of a machine proven in both soft ground and hard rock. The 8.93 m (29.3 ft) diameter Robbins EPB and continuous conveyor system completed what is arguably one of the most difficult legs of the complex Emisor Oriente tunnel, an epic 62 km (39 mi) long conduit that will revamp wastewater treatment for more than 21.2 million people in Mexico City.
The 6 km (3.7 mi) long Lot 5, one of six lots at Emisor Oriente, required the Robbins machine to be launched from the deepest civil works shaft in Mexico, at 150 m (492 ft), and excavated mixed face conditions as well as abrasive basalt rock. “I am proud of concluding the excavation successfully given that this is the section with the greatest depth on the project,” said José Adolfo Méndez Colorado, Superintendente de Maquinaria for contractor Ingenieros Civiles Asociados (ICA). “Robbins Field Service had an important contribution in satisfactorily concluding this section. The machine operation was of primary importance: Field Service personnel know how to operate the equipment accurately for favorable results. The speed with which they detect a problem is a favorable point to reduce downtime on the excavation.”
The complexity of the ground conditions, continued Méndez, required the correct concentration and selection of polymers, a large challenge in itself. Field Service assisted with other issues and with equipment operation: “There were some issues with the screw conveyor conveying mixed ground and also in the articulation system, which were overcome with Field Service experience. They also knew the correct operation of the continuous conveyor system, which kept us to expected performance.”
“We are very proud of this machine as it has worked in two very different worlds,” said Roberto Gonzalez, General Manager for Robbins Mexico. In 2011 the machine originally slated for Lot 5 was fast-tracked to bore a 3.9 km (2.4 mi) long section of Lot 1b—a critical part of the line that needed to become operational right away to prevent chronic seasonal flooding. “The EPB proved itself while using conveyors in the sticky clays of Mexico City with very high percentages of water content, up to 400%.” The machine achieved rates of up to 592.5 m (1,944 ft) in one month—considered a record among the six EPBs (three of them Robbins) used on the project. After completing the bore in just 15 months, the machine was sent to the Lot 5 site, where modifications were made for a section of mixed ground and rock.
Modifications included a high-pressure man lock capable of withstanding 7 bars, chromium carbide wear plates added to the screw conveyor, and grizzly bars added to the cutterhead along with heavy duty cutting tools.
The machine was assembled in a 28 m (92 ft) long assembly chamber at the bottom of the launch shaft and commissioned in August 2014, requiring all back-up gantries to remain at the surface. Two months later in October 2014, after advancing 150 meters (492 ft), the machine and its back-up gantries were completely assembled in the tunnel. One month later, the continuous conveyor system was installed and running. “The assembly of the EPB at Lot 5 has the record of the deepest assembly of a TBM in Mexico. It required great coordination of ICA engineers, high capacity cranes for the assembly and human resources in order to keep to the ten-week schedule for assembly,” said Gonzalez.
With tunneling at Lot 5 now officially concluded there is one more breakthrough remaining before the Emisor Oriente line is complete: An 8.93 m (29.3 ft) Robbins EPB operating at Lot 4 is scheduled to break through this spring. A third Robbins EPB operating at Lot 3 completed its tunnel in 2018.
The Túnel Emisor Oriente (TEO) is the answer to more than 100 years of sinking in Mexico City as the result of drained lake beds and general lowering of the water table. The city’s buildings, main streets and other structures have sunk more than 12 m (39 ft) in that time, and much of the area is vulnerable to flooding. At the same time the area’s gravity-fed wastewater lines have lost their slope and are severely under capacity.
Once tunneling is complete, the resulting TEO will expand capacity, adding 150 m3/sec (5,297 ft3/sec) to the Valley of Mexico system, as well as alleviating the risk of flooding in critical areas. It will also convey wastewater to the country’s largest wastewater treatment plant. The massive tunnel includes 24 shafts, ranging from 23 meters to 150 meters (75 to 492 ft) in depth, plus an exit portal at the treatment plant in the Municipality of Atotonilco, in the state of Hidalgo.
Excavation of Turkey’s longest water tunnel came to an end on December 18, 2018. To get there, a 5.56 m (18.2 ft) diameter Robbins Crossover (XRE) TBM and the contractor JV of Kolin/Limak had to overcome dozens of major fault zones and water pressures up to 26 bar. The completed national priority water line is set to go into operation in March 2019.
The 31.6 km (19.6 mi) long Gerede Water Transmission Tunnel is an urgently needed project due to severe and chronic droughts in the capital city Ankara. Its final leg, a 9.0 km (5.6 mi) section of extremely difficult ground including sandstone agglomerate, limestone and tuff, was just one section in the middle of a tunnel widely considered to be the most challenging ever driven by TBMs in Turkey. “I’ve had the chance to study and visit the majority of mechanized tunnelling projects in Turkey since the 1980s. The Gerede project is one of the most challenging projects among them,” said Dr. Nuh Bilgin, Professor of Mine and Tunnel Mechanization at Istanbul Technical University and Chairman of the Turkish Tunnelling Society.
The Robbins XRE TBM was called in to complete the tunnel, which was at a standstill after using three Double Shield TBMs from another manufacturer. Those machines encountered incredibly difficult geology including massive inrushes of mud and water. The Kolin/Limak JV had to develop a new strategy given the unexpected ground conditions. They contacted The Robbins Company, who suggested a Crossover (Dual-Mode Type) TBM for the remaining section of tunnel. “The Crossover TBM provided great ease and versatility during the entire project with frequently changing ground conditions. The TBM was equipped with features such as increased thrust, two-speed gearbox, and modular screw conveyor. It was capable of giving the necessary responses in different geologies, which was our most important asset in achieving our goal,” said Barış Duman, Project Manager for the Kolin – Limak JV.
“The challenging part for us was to design and manufacture a TBM that could complete the difficult section of the Gerede Tunnel where two other competitor TBMs had failed,” said Yunus Alpagut, Robbins representative in Turkey. The specialized machine was designed to statically hold water pressure up to 20 bar, a failsafe that none of the standard Double Shield TBMs had been equipped with. A convertible cutterhead was also provided that was designed for ease of conversion between hard rock and EPB modes, and with cutter housings that could be fitted with either disc cutters or tungsten carbide tooling. To cope with difficult ground, the Gerede machine was also equipped with the Torque-Shift System, multi-speed gearing allowing the machine to function as either an EPB or a hard rock TBM. This function is done by adding another gear reduction–heavy duty pinions and bull gears accommodate high torque at low speed, allowing the machine to bore through fault zones and soft ground without becoming stuck.
The Crossover machine was assembled in spring 2016 after crews excavated a bypass tunnel to one side of one of the stuck Double Shield TBMs. An underground assembly chamber allowed the machine to be built in the tunnel using Onsite First Time Assembly (OFTA). “The logistics of getting components through the existing tunnel were the most challenging thing. The assembly chamber was 7 km (4 mi) from the portal. The water inflow of 600 l/s (159 gal/s) made it difficult to get the materials to the machine,” said Glen Maynard, Robbins Field Service Site Manager.
Despite the challenges, the machine began boring in summer 2016 and within the first 50 m (160 ft) of boring had successfully passed through the section that buried the original Double Shield TBM. The machine was required to be used in EPB mode as it encountered water pressures up to 26 bars, alluvium, flowing materials, clay and a total of 48 fault zones. Water pressure was lowered by draining the ground water through the rear shield probe drill ports, which were equipped with normally-closed ball valves. Probe drilling was done on a routine basis to get through the ground conditions. “Together with the difficult geological conditions the travel time to reach the TBM within the tunnel had effects on TBM performance. Despite this constraint, the tunnel excavation achieved a best day of 29.4 m (96.5 ft), best week of 134.6 m (441.6 ft) and a best month of 484 m (1,588 ft),” said Duman.
“We had many challenging areas with water and high pressures up to 26 bar along with alluvial material in fault zones. Ground pressure on the shield body caused squeezing conditions in clay. In these regions, we were able to quickly pass through by keeping the TBM advance rate, cutterhead rpm and screw conveyor rotation speed at the ideal level. Ultimately, we think our decision to select a Crossover TBM was correct,” continued Duman.
With tunneling complete, the pipeline is on track to open in March 2019. The tunnel will convey water from the Gerede River to Çamlıdere Dam, which provides potable water for the Ankara city water system.
On October 4, 2018, onlookers watched as a 3.8 m (12.5 ft) diameter Robbins Main Beam TBM completed its epic journey. The TBM, christened “Driller Mike”, after local rapper and activist “Killer Mike”, overcame extremely hard rock conditions along a curving 8.0 km (5.0 mi) tunnel to bolster the city of Atlanta, Georgia, USA’s water supply.
The new tunnel brings the Atlanta Water Supply Program one step closer to increasing the city’s water capacity to between 30 and 90 days depending on daily usage. “Our schedule for the project was very aggressive but the project team stayed together to overcome issues related to the mining of the tunnel,” said Bob Huie, Project Director for the PC Russell JV, the Construction Manager at Risk (CMAR) for the project.
The unique structure of the project team is credited with the overall project success despite challenges. “I’m proud of our team. They had obstacles and challenges and challenging ground, but they stuck together and didn’t give up, and they were successful. There was great leadership and supervision all around,” said Larry Weslowski, Tunnel Superintendent for the PC Russell JV.
The project is only the third such large construction project in the U.S. to use the CMAR structure. The PC Construction/HJ Russell JV was selected as the CMAR for the project, who then purchased the Robbins Main Beam TBM for the tunnel. The designer for the construction works including tunnel and shafts, JP2—consisting of Stantec, PRAD Group, Inc., and River 2 Tap—specified the hard rock TBM. Operation and assembly of the TBM was then sub-contracted to the Atkinson/Technique JV.
The robust TBM was assembled using Onsite First Time Assembly (OFTA) at the massive Bellwood Quarry site with help from Robbins personnel. “The guys built everything per the specs to help with scheduling. It was a challenge but there was no negativity during the process,” said Weslowski. Despite summer temperatures hitting 43 degrees Celsius (110 degrees Fahrenheit) and 100 percent humidity, the TBM was ready to launch by October 2016.
Hard granitic rock challenged the 19-inch disc cutters from the outset. “There was ground so hard that it would take eight hours to go 1.5 m (5 ft). It was between 117 and 310 MPa (17,000 and 45,000 psi) UCS. The beginning of the job was tough,” said Weslowski, but he added that once the learning curve had been overcome “they started breaking project records left and right towards the end. We got a best day of 38.4 m (126 ft). Rates just kept increasing.”Other challenges included groundwater encountered during tunneling. “We did encounter groundwater contamination that required remediation. This remediation work was completed successfully,” said Huie.
With tunneling complete, the USD $300 million project for the City of Atlanta’s Department of Watershed Management is on track to meet its scheduled overall completion date of September 2019. The project will turn the inactive Bellwood quarry into a 9.1 billion liter (2.4 billion gallon) raw water storage facility connecting with the Chattahoochee River and various water treatment facilities.
- Robbins unveils Largest Hard Rock TBM in the U.S. at Mill Creek
- Two Robbins Crossover TBMs to Bore Second Severomuysky Tunnel
- Compact TBM bores longest Rock Tunnel at 2.46 m Diameter
- Major Milestone for Delaware Aqueduct Repair as Robbins Single Shield Completes Excavation
- Robbins EPB caps 62 km of Tunneling with Final Breakthrough at Emisor Oriente