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Robbins Crossover TBM “Rosie” Makes Breakthrough at Akron OCIT
On August 29, 2018, a 9.26 m (30.4 ft) diameter Robbins Crossover (XRE) TBM crossed the finish line at the Akron Ohio Canal Interceptor Tunnel (OCIT). A press day followed on September 5, where companies and members of the media were invited to view the giant machine. The machine—dubbed “Rosie” in honor of Rosie the Riveter, an icon representing American women who worked in factories and shipyards during World War II—overcame tough ground conditions during the bore.
“One of the most challenging aspects of this job was that we launched right into the most difficult part. We had 60 m (200 ft) of soft ground, a very short reach, and then from there we went right into a mixed face for 180 m (600 ft),” said David Chastka, Project Manager for Kenny Construction, a joint venture contractor on the project with Obayashi. “It took everybody we had in the industry, everybody from Robbins, to fight through that first 240 m (800 ft).”
The TBM was designed for the project’s geology, which transitioned from soil to partial face shale to full face shale rock. The Crossover XRE included features of both EPB and Hard Rock Single Shield TBM types, with a versatile cutterhead that could be configured for hard rock or soft ground conditions. While in soft ground and mixed face conditions the machine operated in closed mode, but once it hit solid rock crews switched excavation to open mode.“The machine had the power to get to the other side and made advance rates we never thought we were going to get. It was very successful in hard rock,” said Chastka. Advance rates once in full-face shale rock reached a high of 34 m (111 ft) in one day (two 10-hour shifts). Muck removal was achieved using a Robbins continuous conveyor, and conveyor availability remained high throughout the project.
“I am most proud of the team that I have had the pleasure of being a part of,” said Don Smida, Robbins Field Service Technician. “The overall scope of a project of this scale is immense, and the amount of daily cooperation & hard work that has been asked of The Robbins Company, the local unions, city staff, and Kenny-Obayashi is extremely important in reaching our common goals. I think we should all be proud of our teamwork going forward from a successful completion of the tunnel and into a successful disassembly of Rosie.”
Now that tunneling is complete, the machine will be disassembled and removed from its retrieval shaft this autumn. “The Ohio Canal Interceptor Tunnel is the largest public improvement project in our City’s history and a significant investment in our environment and infrastructure that will benefit Akron residents and businesses for generations to come,” said the City of Akron’s Mayor Daniel Horrigan. “Projects of this kind are inherently dangerous, and I am incredibly proud that the tunneling portion was completed without any major injuries, thanks to a dedicated team of professionals. And although Robbins is an international company with worldwide impact, we were pleased to be able to work with a local Northeast Ohio firm on this significant project.”
The OCIT Project for the City of Akron, Ohio, USA consists of the construction of a conveyance and storage tunnel system to control Combined Sewer Overflows (CSOs) for several regulators in the downtown Akron area. The EPA-mandated project includes the 1.89 km (1.17 mi) conveyance and storage tunnel, as well as drop shafts, diversion structures, consolidation sewers, and related structures.
Nepal’s First TBM bores 1,000 Meters in One Month
Nepal’s first tunnel boring machine, a 5.06 m (16.6 ft) diameter Robbins Double Shield, is living up to the nation’s high expectations. The TBM, supplied in summer 2017 for the Bheri Babai Diversion Multipurpose Project (BBDMP), recently bored over 1,000 m (3,280 ft) in one month and has been averaging an impressive 800 m (2,630 ft) per month. The project is owned by the Government of Nepal’s Department of Irrigation (DOI) and operated by contractor China Overseas Engineering Group Co. Ltd. Nepal Branch (COVEC Nepal).
The decision to use a TBM for the BBDMP project—designated by the government as one of Nepal’s 11 National Pride Projects—was a departure for a nation where drill & blast has long been the preferred tunneling method. Early studies done on the tunnel path predicted that drill & blast excavation of the 12.2 km (7.5 mi) tunnel would take close to 12 years to complete. The tunnel is located in the Siwalik Range, part of the Southern Himalayan Mountains, where geology consists of mainly sandstone, mudstone, and conglomerate.
Mr. Wang Wu Shui, General Manager for COVEC Nepal, cited several factors that have contributed to the good advance rates so far, “In China, there is a proverb about TBM construction: ‘geology is the premise, equipment is the foundation, and talents are the key’. The great advance rates achieved at present mainly lie in preliminary planning, process control, and professional construction personnel.” Shui added that technical training and guidance are provided for each position so that all personnel can fully understand their job and team responsibilities. If unforeseen circumstances arise and there is no operator for a certain position, others have enough training to fill the role.
To ensure the best TBM performance and to prevent downtime, machine maintenance occurs daily at a fixed time. Geological engineers are sent to analyze the ground conditions twice daily so that construction personnel can adjust the tunneling parameters and prepare for auxiliary measures if geological changes are predicted.
The ground conditions during the record-setting month consisted mainly of sandstone and mudstone, but that is set to change. At about the 5.8 km mark, the machine will encounter a major fault zone known as the Bheri Thrust. Clay and water ingress are expected throughout the fault, which is about 400 to 600 m wide.
COVEC Nepal are prepared for the conditions and have worked out efficient tunneling logistics to decrease downtime. “The two working procedures of tunneling and segment erection are carried out simultaneously under the double shield tunneling mode, and the time to erect a ring of segments is 15 minutes in general,” said Shui. “Under the single shield tunneling mode, segment erection comes after tunneling in a sequential process, but the segment erection time is still about 15 minutes.” To further reduce time, consolidation grouting is carried out in advance during daily maintenance to avoid the impact of downtime for grouting on the overall construction progress.
Once complete, the BBDMP will irrigate 60,000 hectares of land in the southern region of Nepal, and benefit an estimated 30,000 households. It will divert 40 cubic meters (1,400 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 water will also be used for hydroelectricity, with a generating capacity of 48 MW benefiting the country with NPR 2 billion (20 million USD) annually. The initial success of the TBM operation has already inspired developers and contractors to opt for TBMs over conventional excavation methods on upcoming Nepalese tunnels.
Twin Robbins Crossover TBMs to bore on Mumbai Metro Line 3
On June 11, 2018, a Robbins Crossover XRE destined for Line 3 of India’s Mumbai Metro arrived in Mumbai port following a successful factory acceptance test in April. The machine, combining features of a hard rock Single Shield TBM and an Earth Pressure Balance Machine, is one of two 6.65 m (21.8 ft) Crossover machines that will bore under contract UGC-01. Operation of these two machines will be carried out by Larsen & Toubro, part of the Larsen & Toubro -Shanghai Tunnel Engineering Co Joint Venture (L&T-STEC JV). The Robbins Company will provide key personnel for the initial boring phase. “During the factory acceptance testing, we observed that the machine and back-up system are robust enough for hard rock tunneling,” stated Palwinder Singh, Head of Tunnel Operations for L&T-STEC JV.
During the bores, consisting of parallel 2.8 km (1.7 mi long) tunnels, geologic conditions will include mixed ground and possible water pressures up to 2 bar. According to Singh, “A Crossover XRE was chosen because of the expected geology,” which includes basalt rock and transition zones consisting of black carbonaceous shale, tuff, and breccia. Rock strengths are anticipated to range between 15 MPa and 125 MPa (2,200 and 18,100 psi) UCS. The machines will bore with only 15 to 20 m (50 to 70 ft) of cover above the tunnel and the structure will be lined with reinforced concrete segments in a 5+1 arrangement.
The metro tunnels will run between the Cuffe Parade Station and Hutatma Chowk station, passing through the Vidhan Bhavan and Church Stations. Both Crossover machines will be launched from the same 25 m (82 ft) deep by 22 m (72 ft) long shaft at the Cuffe Parade Station. “The limited length of the shaft requires running the TBMs for the first 100 m (328 ft) with some or all the back-up decks at the surface,” said JP Bayart, Robbins Project Engineer. “The TBMs and back-up systems are connected with umbilical cables and hoses.”
The TBMs will begin their excavation in hard rock mode. “Each cutterhead is optimized for operation in rock, as this is what is expected. The machines can also operate in soft ground thanks to the screw conveyor with bulkhead gate and discharge gate,” said Bayart. “The Robbins Torque-Shift System, consisting of two-speed shifting gearboxes coupled to the main drive motors, allows for the high cutterhead torque required for soft ground operation.” The face of each machine is equipped with six muck buckets and six large internal muck loading plates. This design, in combination with the screw conveyor located at the centerline of each machine, will allow for the option of fully emptying the cutterhead chamber, resulting in minimal wear when EPB mode is not required. Muck will be removed from the tunnels via muck cars.
Assembly and launch preparations for the first XRE TBM began on 20 June and are estimated to take about six weeks. The second Robbins XRE TBM underwent factory acceptance testing at the end of May and will arrive at the jobsite at the end of July for its assembly. “Our target is to achieve an average of 250 m (820 ft) of boring per month,” said Jim Clark, Robbins Projects Manager India. “The target to complete the boring operations is 20 months, which includes the additional time required for the short start-up using umbilicals on the initial drives, dragging the machines and re-launching through three stations.” Contractor L&T plans to work crews on double shifts to cover a full day of operations in order to keep to this timeline. The machines will join two Robbins Slurry machines boring a separate contract of the Mumbai Metro Line 3. The first of those machines will be launching in August 2018. The Metro Line 3 project as a whole is estimated to be completed by 2021.
Europe’s First Crossover TBM breaks through at Moglicë Headrace Tunnel
On May 3, 2018 a 6.2 m (20.3 ft) diameter Robbins Crossover (XRE) TBM broke through into an underground chamber, marking the completion of the first TBM-driven tunnel in Albania. The TBM, operated by contractor Limak, was also the first Crossover machine to operate in Europe, and bored through geology including ophiolite, sandstone, breccia and siltstone flysch.
“The cutterhead and cutters have achieved outstanding performance,” said Engin Gur, TBM Manager for Limak. The TBM achieved rates as high as 648 m (2,126 ft) per month in April 2018, and as much as 37.4 m (122.7 ft) in one day. The Crossover TBM did not encounter high-pressure water and was thus used in hard rock Double Shield mode throughout tunneling.
“The TBM performed very well, as did a Robbins-supplied adit conveyor that operated in a 180-degree continuous curve. It was impressive,” said Max Walker, Robbins Field Service Superintendent. Several field service personnel remained onsite throughout operation of the TBM to provide guidance and trouble-shooting.
The machine was launched in November 2016 following Onsite First Time Assembly (OFTA), which enabled the machine to be initially assembled at the jobsite. The crew ramped up production slowly over the next 230 m (755 ft). “Ground conditions were good and we did very few cutter changes—only 20 cutters were used during the bore,” said Walker. Two-stage grouting was carried out as the TBM bored and lined the tunnel in three 8-hour shifts. “The personnel on this project have created a friendly work environment; they’ve made it enjoyable coming to work each day. They’re good guys to work with,” he added.
While the TBM did not need to be sealed, the unique machine design took into account a predicted high risk of water inflows. The Crossover XRE machine used a belt conveyor and not a screw conveyor for muck removal, so the muck chute needed to be able to be sealed off in the case of an inrush of water. The bulkhead was thus designed with a large sealing gate just above the belt conveyor. These pressure-relieving gates could also be used in a semi-EPB mode: As the pressure built in the cutting chamber, the gate would then be opened by the pressure, and material would spill onto the belt. As the pressure lowered, the gates would then automatically close, again sealing off the chamber. In extreme cases, the gates could be sealed and the probe/grout drills could be used to drill, grout, and seal off water. Additionally, the gripper shoes and inner telescopic shield were designed with inflatable seals to further protect against inrushes of water.
With the breakthrough now complete, grouting will continue behind the TBM segments. No additional lining will be added, and the tunnel is expected to become operational by May 2019.
The 6.7 km (4.2 mi) long Moglicë headrace tunnel is part of the Devoll Hydropower Project, a Build-Own-Operate-Transfer (BOOT) scheme to construct two hydropower plants along the Devoll River, named Moglicë and Banja. The project is owned by the Norwegian power company Statkraft AS. The completed Devoll Hydropower Project will increase Albania’s electricity production by 17% and will have an installed capacity of 242 MW.
Robbins TBM uncovers Spectacular Cavern at Galerie des Janots
A rebuilt Robbins 3.5 m (11.5 ft) diameter Main Beam TBM has yet another milestone to add to its storied career: an unexpected cavern, encountered and successfully passed through.
Contractor Eiffage Civil Engineering is operating the machine, which launched in 2017 for the Galerie des Janots project in La Ciotat, France. The cavern, studded with stalactites and stalagmites and measuring 8,000 cubic meters (283,000 cubic ft) in size, was grazed on the tunneling operation’s left side. The crew named the cavern “grotte Marie Lesimple” after their site geologist.
“We hit the corner of it. To cross it, we had to erect a 4 m (13 ft) high wall of concrete so the TBM would have something to grip against,” explained Marc Dhiersat, Project Director of Galerie des Janots for Eiffage. A small door allowed access inside the cavity, which formed naturally at a point 60 m (200 ft) below the surface. The TBM was started up and was able to successfully navigate out of the cavern in eight strokes without significant downtime to the operation.
“This is certainly unusual, to come across a cavern of this size and significance. It is somewhat related to the geology, with karstic and volcanic formations having the most potential for underground cavities,” said Detlef Jordan, Robbins Sales Manager Europe. Karst cavities were a known risk during the bore, but the cavern was not shown in vertical borehole reports conducted from the surface along the alignment.
A further 1.8 km (1.1 mi) will need to be tunneled before the 2.8 km (1.7 mi) tunnel is complete. “It is possible there could be more unknown caverns. We have a geotechnical BEAM system on the machine, and are conducting probe drilling, shotcreting, and maintenance in a separate shift,” said Dhiersat. The BEAM system, standing for Bore-tunneling Electrical Ahead Monitoring, is a ground prediction technique using focused electricity-induced polarization to detect anomalies ahead of the TBM.
The crew encountered difficult ground conditions early on in the bore, consisting of limestone with powdery clays. “When the machine is boring it does well. We have good production and it’s a good machine for hard rock. But sometimes it’s not hard rock that we encounter,” said Dhiersat. The weak rock and clay conditions necessitated ground support including resin-anchored bolts and rings in bad ground, topped with a 10 to 15 cm (4 to 6 in) thick layer of shotcrete. Despite five months of poor ground conditions, Eiffage is optimistic that conditions will improve and the tunnel will be complete in the next four to five months.
Galerie des Janots is one of the 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 future Janots gallery 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 completed tunnel will pass under Le Parc National des Calanques, with cover between 15 and 180 meters (50 to 600 ft), in order to replace the pipes that are currently being utilized for the water supply networks. “The current pipes have a capacity of transit limited to 330 liters (87 gallons) per second, which is largely insufficient in the summer period. The objective of the operation is to secure the lines and increase capacity to 440 liters (116 gallons) per second,” said Dhiersat.
Veteran Robbins TBM plays a Main Role in Ending Residential Flooding
In Chicago, Illinois, USA Kenny Construction is nearing completion on the Albany Park Stormwater Diversion Tunnel. The project, owned by the Chicago Department of Transportation, will divert water from the Albany Park neighborhood, which has long been plagued by flooding. Plans for the tunnel began in 2013, after flood conditions became so severe that residents had to be evacuated from the area by boat. The tunnel is expected to be functional by April 2018.
A Robbins Main Beam Hard Rock TBM bored the tunnel and broke through at the end of August 2017, bringing the project one step closer to completion. The TBM, also known as “Keri,” has been owned by project contractor Kenny Construction since the 1990s and has been used on several projects prior. “The machine holed through into the inlet shaft,” said Clay Spellman, Project Manager for Kenny Construction. “We excavated the shaft as part of the project. The machine has since been disassembled and removed.”
For the Albany Park Project, Keri was rebuilt by Kenny Construction with size modifications designed by Robbins. Robbins took an existing cutterhead, repaired it, and then added segments, taking it from 5.2 m (17.2 ft) to 6.2 m (20.4 ft) in diameter. “Extensive modifications were also made underground to the machine to be able to install rock dowels and stand the ring steel under the roof shield,” added Spellman.
“Rebuilding TBMs has always been a core part of Robbins’ business. Most customers immediately recognize that a rebuilt machine with updated systems can offer exceptional value without increasing risk, and a rebuilt machine can usually be delivered faster,” said Robbins Engineering Manager Steve Smading. “While the financial and schedule advantages are obvious, the flexibility of used equipment may be less obvious. Boring diameters can be increased or decreased and machine configurations can even be changed. For example, a Single Shield can be reconfigured as a Double Shield or vice versa, and a Main Beam TBM can be reconfigured as a shielded machine. Soft ground machines can be configured for different geologies and can be set up as either Slurry or EPB.”
Over 50 percent of all Robbins Main Beams ever manufactured have been used on three or more projects. Incredibly, many Robbins TBMs that have been used on multiple projects are approaching over 50 km (31 mi) of use. Prior to its ownership by Kenny, Keri has successfully bored tunnels in the Dominican Republic, Saudi Arabia, New York, and Chicago—totaling at least 19.5 km (12 mi) of tunnel.
Due to the project location in a residential neighborhood, there were restrictions in place as to when the machine could operate and the frequency at which blasting would be allowed per day. Despite these limitations, the TBM achieved a best day of 39.5 m (129.7 ft) and a best week (5 days) of 146.4 m (480.4 ft). The machine bored through dolomite with an average compressive strength of 64 MPa UCS (9,300 psi). “During boring we encountered approximately 30.4 m (100 ft) of fractured ground that had to be supported with rolled channels, straps, and 19 full circle steel rings,” said Spellman.
The drainage tunnel starts in Eugene Park and extends for approximately one mile under Foster Avenue to the North Shore Channel. When the Chicago River’s water levels reach flood stages—exceeding 2 m (7 ft)—the tunnel will divert a flow of 65 cubic meters (2,300 cubic ft) of water per second, avoiding Albany Park, then deposit it into the Channel. The tunnel will essentially be transferring the water where it would have ended up, without damaging the residential area or adversely affecting the river’s wildlife.
Robbins Main Beam Breaks Records in China
In Jilin, one of the three provinces of Northeast China, a 7.9 m (26 ft) diameter Robbins Hard Rock Main Beam TBM has achieved a national record for 7 to 8 meter (23 to 26 ft) machines: 1,423.5 m (4,670 ft) in one month. The record tops a previously-set achievement on the same project from earlier in 2017, when the TBM advanced at a rate of 1,336.8 m (4,386 ft) in one month.
The world record for the size class is held by another Robbins machine, set more than 20 years ago at the Tunnel and Reservoir Plan (TARP) in Chicago, Illinois, USA, for 1,482 m (4,862 ft) in one month. However, given the differences in rock conditions this Jilin project record is very significant. At TARP the rock was relatively homogeneous dolomitic limestone averaging 145 MPa/21,100 psi with occasional rock bolts; at Jilin the rock types were rated from 35 to 206 MPa UCS (5,100 to 30,000 psi), and identified as tuff, granite, sandstone, and andesite with multiple fault zones—conditions requiring nearly continuous ground support.
Despite the difficult conditions, the Jilin machine has achieved an average monthly advance rate of 708.3 m since the start of boring in March 2015—more than three times the average monthly rate of a Drill & Blast operation on another section of the project. “It is now very evident that well-equipped, open-type Main Beam TBMs with specialized features for difficult ground can traverse faults and large water inflows much faster than conventional tunneling methods. This fact, coupled with the high performance capabilities as demonstrated at Jilin, lowers the cost and time to complete long tunnels in difficult ground,” said Robbins President Lok Home.
The Jilin Lot 3 tunnel, which is being bored as part of a water conservation project, will be 24.3 km (15 mi) long when complete. Under contractor Beijing Vibroflotation Engineering Co. Ltd. (BVEC), the machine has excavated 14 km (8.7 mi) of the tunnel as of January 2018.
Throughout its bore, the Main Beam is expected to traverse a total of 24 fault zones. The TBM was designed accordingly, and is equipped with four rock drills, McNally pockets in the roof shield for the ability to install McNally slats, a ring beam erector, and a shotcrete system. The McNally slats were used in difficult ground encountered in the tunnel.
The McNally Roof Support System was designed and patented by C&M McNally and licensed for exclusive use on Robbins TBMs in certain markets. By replacing the roof shield fingers on a Main Beam TBM, the McNally system prevents movement of loose rock in the critical area immediately behind the cutterhead support. The system has been tested and proven on projects worldwide—including the world’s second deepest civil works tunnel, the 2,000 m (1.2 mi) deep Olmos Trans-Andean Tunnel in Peru—to increase advance rates while still maintaining worker safety on Main Beam machines in difficult rock conditions.
The Jilin TBM’s first fault zone was encountered after just 87 m (285 ft) of boring, requiring cooperation between the owner, Jilin Province Water Investment Group Co., Ltd., contractor BVEC, and Robbins field service. Water inflows and collapsing ground in a section measuring 1,196 m (3,926 ft) long were resolved with a combination of McNally slats, grouting, and consolidation of the ground ahead of the machine. Ground support overall consists of wire mesh and shotcrete. Tunnel Reflection Tomography (TRT)—a method of ground prediction using seismic waves—is also being used to detect changing conditions ahead of the TBM.
Despite the initial challenges, the TBM is now achieving between 40 and 60 m (130 to 197 ft) advance per day. “My colleagues and I all feel that the Robbins TBM is very easy to operate. All components of the system work well during operation, which has ensured our good progress,” said by Tao Yong, BVEC Jilin Lot 3 TBM Site Manager.
The Jilin Lot 3 tunnel is part of the Jilin Yinsong Water Supply Project, which will convey water to the central cities of Jilin Province. The large-scale, trans-regional water diversion project is the longest water supply line, measuring 263.5 km (163.7 mi), with the largest number of recipients benefiting from it in the history of Jilin Province. The construction project will divert the water from Fengman Reservoir at the upper reaches of Di’er Songhua River to central regions of Jilin Province experiencing chronic water shortages. These regions include the cities of Changchun and Siping, eight surrounding counties, and 26 villages and towns under their jurisdiction. Tunneling is expected to be complete in late 2018.
Robust Robbins EPB Completes Third Bore for Chennai Metro Project
On Tuesday, October 31, 2017, a 6.65 m (21.8 ft) diameter Robbins EPB TBM broke through at Chennai Metro, making this the third tunnel the machine has bored for the project and for contractor Afcons Infrastructure Ltd. The three separate bores for the EPB are part of an increasing trend, as many Robbins EPBs have been used on multiple tunnel drives with good performance. Robbins EPBs are built one third heavier than any other EPB on the market and are designed for 10,000 hours of usable life, making them ideal machines for use over many kilometers. “Robbins is known for designing resilient machines,” said Mr. Gopal Dey, Afcons Senior Manager. “For this project, we needed a machine that was specifically tailored to project conditions from soft clay to mixed ground with rock. Robbins EPB TBMs have unique design features that optimize the machine for the geology.”
After completing its original twin tunnels, the EPB was refurbished in preparation to bore its latest 1.8 km (1.1 mi) section. During refurbishment, the inner seal greasing system was changed from auto to manual mode and the foam nozzle system was modified. These changes optimized the machine for excavation in the highly variable mixed face conditions encountered in the first two tunnels.
The EPB was launched on February 3, earlier this year. According to contractor Afcons, the machine faced a major challenge right out of the gate. “When the TBM came out of the launching shaft, a few rings were erected and then the machine had to cross a live railway track, which meant there would be a possibility of ground settlement,” said Afcons Director, Mr. Manivannan. “At this stage, we had to closely monitor TBM face pressure and advance the machine at a uniform rate to ensure proper primary grouting.” The bore’s geology mainly consisted of clayey sand and about 60 meters (197 ft) of mixed ground.
“We [Afcons] chose this machine for this project due to the underground geology in Chennai, which continuously changes from soil to mixed ground,” said Mr. Dey. “We also liked that Robbins EPB machines are designed with active articulation to allow the machine to turn or steer with ease.” During active articulation, thrust cylinders react evenly against the entire circumference of the tunnel lining, even in a curve—a design that eliminates the problem of tunnel lining deformation. “This feature enabled the machine to negotiate through well-controlled conditions,” added Mr. Manivannan.
With all three tunnels, Robbins Field Service members were on location to assist and support as required. During the course of each bore, Robbins was there to advise Afcons on how best to maneuver through challenging ground and provide instruction for machine operation. The ability of the contractor and manufacturer to work well together, as Robbins and Afcons have throughout their contracts, was critical to the good advance rates. The result was a robust machine that advanced at rates of 80 mm (3 in) per minute in challenging conditions.
This latest tunnel connects multiple stations along the metro line, starting from Washermenpet through to Sir Theagaraya and to Kurukpet. The Chennai Metro Project will provide much needed transportation to a rapidly developing city.
A 100th System for Robbins Continuous Conveyors
On October 18, 2017, a Robbins 9.26 m (30.4 ft) diameter Crossover machine started up at the Akron Ohio Canal Interceptor Tunnel (OCIT) in Ohio, USA—but the startup wasn’t the only milestone. Running behind the Crossover TBM is the 100th Robbins Continuous Conveyor system supplied for muck removal. The side-mounted conveyor is a design standard, but the landmark is a significant one: “With this system we have provided more conveyors than any other TBM conveyor supplier,” said Dean Workman, Robbins Director of Conveyors, Cutters, & SBUs. Counting conveyor systems the company has on order but has not yet delivered, that number is now well above 100, Workman added.
The Akron OCIT conveyor system consists of the belt plus a main drive, splice stand, storage unit, and advancing tailpiece, operating through several curves requiring patented self-adjusting curve idlers that correct themselves based on varying belt tension and belt load. The system discharges onto a customer-supplied overland conveyor, which delivers the muck to a large storage yard near the portal site. The belt was designed to handle variable geology, from soft soils to partial face rock and finally full-face shale rock.
The 100th conveyor system has been refurbished and customized for the job in a process that Robbins has been perfecting for decades: “We design our conveyor systems to last for five to ten years, but many last for decades longer. We have systems utilizing components that have been in operation for 30 years. We haven’t reached a limit for many of our systems—for example we had a specialized conveyor system built more than a decade ago for the Parramatta Rail Link in Sydney, Australia. Those components were refurbished for a job in Atlanta, Georgia, and now they are being used at the Dig Indy tunnels in Indianapolis, Indiana. These are long and challenging tunnel drives and the components are up to it.” While the Akron OCIT conveyor is just beginning to haul muck, it is sure to be a benefit throughout the project’s varying ground conditions.
The conveyor in Akron is also part of a long history for Robbins conveyors—the first of which (not counted in the list of 100) was the first ever continuous conveyor system used behind a TBM. That prototype, developed by founder James S. Robbins in 1963, was successfully used behind the 11.2 m (36.7 ft) diameter Main Beam TBM at the Mangla Dam project in what was then known as West Pakistan. While conveyors would not be adopted as a standard method of muck removal for many years afterward, the project laid the groundwork for future success.
Today’s conveyor systems are capable of spanning dozens of kilometers and hauling 1,800 metric tons (2,000 US tons) an hour or more. It’s a legacy that Workman sees will continue to grow: “This is my 20th year with Robbins and I remember when we started our conveyor list. It is amazing to look at all of the jobs and things we’ve done. It’s amazing to see what these systems can do.”
Robbins Slurry TBM ramps up for Mumbai Metro Line 3
The first of two Slurry TBMs, a rebuilt 6.65 m (21.8 ft) diameter machine, passed its factory acceptance on September 4, 2017 in Singapore. The machine, fitted with a Robbins cutterhead and outer shields, is destined for the Mumbai Metro Line 3 under contract UGC03 for the Dogus-Soma JV (DSJV), and will begin excavation in late 2017. The factory acceptance for a second 6.65 m (21.8 ft) diameter Slurry TBM will be conducted by the end of 2017.
The on-time delivery of the first machine is just the beginning of partnership that will span years. “There are few companies in the international arena that are as professional as Robbins. Robbins has been very helpful to DSJV since the inception of the project and will be our partners until the end of the contract. Robbins’ presence in India including field service crews will be a great help for us in future,” said Mr. DV Raju, Senior Vice President for SOMA.
The two machines will excavate parallel 3.5 km (2.2 mi) long tunnels between Mumbai Central and Worli station sites, passing through three intermediate cut and cover stations on the way. Ground conditions consist of fresh to weathered basalt and breccia up to 100 MPa UCS with water pressures up to 3 bar.
The JV selected Slurry machines for their contract due to the challenging ground conditions expected. “I have worked with Slurry TBMs on similar geology globally. Slurry TBMs have real power and will suit the hard rock geology of our Mumbai Metro contract 3. The water table and variable geology, especially basalt of higher hardness, can be easily tackled by Slurry TBMs,” said Mr. Tamay Sayin, Project Manager for DSJV. The cutterheads of the machines are fitted with wear protection, wear detection bits, and Robbins 17-inch disc cutters for the conditions. Grizzly bars will limit the size of boulders that can enter the cutterhead to 250 mm (9.8 in). The slurry systems includes rock crushers as well as abrasion-resistant plating in high-wear areas.
The two TBMs are the first of a total of four machines being provided by Robbins for the Mumbai Metro Line 3. Another two 6.65 m (21.8 ft) diameter Crossover XRE machines will bore parallel 2.8 km (1.7 mi) tunnels on a separate contract in 2018. “Mumbai Metro is one of the most prestigious metro works in the country, and Robbins’ involvement in providing suitable machines and associated services is an honor,” said Kapil Bhati, Managing Director for Robbins India.
The 33.5 km (20.8 mi) long Line 3 of Mumbai Metro being constructed by the Mumbai Metro Rail Corporation (MMRC) will consist of 26 underground stations and one at-grade station that will reduce heavy traffic and rail congestion between Bandra and Churchgate areas of the city. A total of 17 TBMs are being procured to bore various sections of the tunnels, which will be excavated at average depths of 15 to 25 m below the city. The entire line is expected to be operational by 2021.