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On January 27, 2016, a Robbins mixed ground EPB broke through at Chennai Metro, finishing up a challenging second drive that saw the full gamut of difficult conditions. The 1,027 m long second drive for the machine was part of Lot UAA-01 on Line 1 of the city’s metro, consisting of two parallel 1.0 km (0.6 mi) tunnels running from the Washermanpet area towards Chennai International Airport. Contractor Afcons Infrastructure Ltd. reflected on the breakthrough: “We are really proud of our executing team, who have maintained a high standard of quality. We didn’t record any water leakage or settlement at the surface, and we have demonstrated a high standard of safety in the tunnel during construction,” said Mr. Gopal Dey, Sr. Manager for Afcons.
The 6.65 m (21.8 ft) diameter Robbins EPB was designed to excavate granite, sand, silt, and clay with boulders up to 300 mm (12 inches) in diameter. The specialized design utilized a combination of 17-inch diameter disc cutters as well as soft ground tools. Small grippers located around the circumference of the machine’s shield allowed for cutterhead stabilization in harder ground, while additionally reacting the forces needed to pull the cutterhead back from the face in difficult conditions.
The TBM was launched on its initial drive in January 2012 from a 28 m (92 ft) deep starting pit. Challenges began nearly from the outset. The TBM bored into mixed face conditions that contained varying strengths of granite, from weathered to hard granite of 150 MPa (21,700 psi) UCS. The unexpectedly hard rock caused high cutter consumption rates and slowed advance.
A crew of Robbins Field Service personnel and engineers assisted Afcons in remedying the problem. Robbins India provided a geologist who carried out face mapping for the whole of the first drive, in both hyperbaric and open mode conditions on a daily basis. The data not only assisted the crew in operating the TBM, but also provided a comprehensive geological record for the second drive. With the data gleaned from the geological investigation, Robbins was able to advise Afcons on the optimal operating parameters to get through the difficult conditions, including cutterhead RPM, thrust pressure, penetration rate, and cutterhead torque. The parameters also resulted in a reduced cutter consumption rate.
Contractor Afcons was pleased with the help they received: “The Robbins Field Service team extended very good services to us, particularly in the mixed face & full face rock when they deployed their Geologist for face mapping. This helped us to understand the strata ahead of us, and based on this the TBM advance rate and operating parameters were decided,” said Mr. V. Manivannan, Executive Vice President for Afcons.
The TBM was launched on its second tunnel in February 2015. Conditions were just as difficult as the first drive, but now the team approached it with experience: “We experienced very high water pressure in this alignment, as the water table in Chennai is just 1.5 m (5 ft) underground and the strata above the crown included silty sand, clay and weathered rock. It was very important for us to maintain the earth pressure to reduce the inflow of water, and to avoid any settlement on the surface with proper grouting,” said Dey. Despite the challenges the TBM was able to complete a section below the Koovam River without any water flowing into the tunnel. The machine achieved up to 12.6 m (41 ft) in one day and 62 m (203 ft) in one week.
The TBM broke through into a receiving shaft, utilizing a unique setup for the second time that had the machine emerging under water. “These were the first breakthroughs in India under wet conditions in the retrieval shaft, which is 30 m (98 ft) below the ground level. The retrieval shaft was filled with Bentonite slurry 10 m (33 ft) from the base slab in order to arrest water entry from outside the diaphragm wall,” explained Manivannan.
The completed sections of tunnel will now be commissioned as part of Line 1, a 32.1 km (19.9 mi) long route in total with 14.3 km (8.9 mi) underground and a total of 17 stations. The southeastern Indian city of Chennai is a rapidly growing technological and industrial center with a population of more than 8.2 million people and a high need for alternate means of transportation.
In a large November 2015 ceremony attended by the mayor of Montreal, Quebec, Canada, and representatives from local media outlets, the Rosemont Reservoir tunnel construction came to a close. The challenging project gave good cause for celebration as crew members crowded around the cutterhead of the 3.0 m (9.8 ft) diameter Double Shield TBM that had emerged into an exit shaft.
Local contractor Foraction, Inc., headed the excavation of the 4.0 km (2.5 mi) long tunnel with a TBM launch in December 2014. Roger Lepinay, Equipment Manager for Foraction, Inc., praised the Robbins disc cutter wear in both limestone and harder rock formations: “I was impressed by the cutters, it was a nice surprise. They were quite long-lasting compared to other cutters I have used on jobs in the past.”
Lepinay characterized the ground as “almost ideal”, with a few difficult sections. “Below Montreal there is mostly thinly bedded limestone, with some shale and intrusive igneous rocks, mainly dykes and sills,” explained project geologist Brigitte GagnÃ© for company Exp Service Inc. While the limestone averaged 100-150 MPa UCS, rock in the intrusives ranged from 100-300 MPa. The dykes and sills were as small as a few centimeters wide and as large as 8 to 10 m (26 to 33 ft) wide. The contractor was able to successfully navigate these sections despite the varying rock strengths. Even with geologic challenges including some water inflows and over-break in small sections, the contractor was able to achieve advance rates of up to 38 m (125 ft) per day in two shifts of 9.5 hours each. Much of the ground was self-supporting, though the contractor installed rock bolts every 2.5 m (8.2 ft) into portions of the tunnel crown, while mesh, rock bolts, and steel sheets were used in the sections of unstable rock.
The long tunnel drive at small diameter was carefully planned to optimize logistics. The contractor utilized a muck train that could accommodate two pushes worth of excavated material. The first kilometer (0.6 mi) was ventilated from the launch shaft, while three surface-driven 800 mm (32 in) diameter surveying wells at the 1, 2, and 3 km (0.6, 1.2, and 1.9 mi) marks ventilated the rest of the tunnel as the TBM progressed.
With the breakthrough, an important phase of the Rosemont Reservoir project is complete. The reservoir itself was built in 1960 to increase water supply to the city and a geotechnical study for the tunnel was carried out in 1977. However, other major infrastructure projects soon took priority and the project was placed on hold. By 2010, the population of the city had increased dramatically and problems with the existing reservoirs put the project back on the fast track. The large reservoir that sat idle for decades will now be used to improve much of the city’s water supply.
As of mid-January the contractor is working to ready the tunnel for installation of the carrier pipe, consisting of 2.13 m (84 in) I.D. pre-stressed concrete cylinder pipe (PCCP). Crews will then grout the pipe in place. There will be several more work stages to be carried out before the Rosemont Reservoir is finally reconnected to the water main network in 2019.
A crowd of crew members gathered to celebrate in front of a newly emerged hard rock TBM on December 10, 2015 in northern Norway, but their celebration was about more than just a breakthrough. The 7.2 m (23.6 ft) diameter Robbins Main Beam machine had traversed incredibly hard rock, water inflows, and more to become the first TBM in the country to break through in over 20 years.
The 7.4 km (4.6 mi) long headrace tunnel for the RÃ¸ssÃ¥ga Hydroelectric Project offered up a number of challenges to the crew. “We bored through hard, quartz-rich rock with rock strengths up to 300 MPa (43,500 psi) UCS and softer karstic limestone with water ingress,” explained Tobias Andersson, TBM Manager for contractor Leonhard Nilsen & SÃ¸nner (LNS). Despite the geological challenges, the TBM performed very well and achieved a record production of 250 m (820 ft) advance in one week, as well as a high of 54 m (177 ft) in one day. Advance rates consistently ranged from 180 to 200 m (590 to 660 ft) per week throughout the project.
The hard and abrasive rock required both fine-tuning of the disc cutters and a learning curve with regards to TBM operation. “We overcame the rock by adapting driving parameters to the different geology, cutter wear and vibrations of the machine. We had regular maintenance, but most important of all we got really good at changing the cutters, with times down to 10 minutes per cutter change, which couldn’t have been done without good team work,” said Andersson.
It was the many cutter changes that prompted the close-knit team of LNS and Robbins to look for a better solution. “Extremely hard rock (above 250 MPa/36,300 psi) will always be a great challenge for any cutter. The very special features of the rock encountered combined with the extreme hardness made us go back to the Robbins Cutter Department to develop special cutter rings for the project. These rings increased the cutter life significantly for the project and contributed to the good production,” said Sindre Log, General Manager of Robbins Norway.
The Robbins TBM was launched following Onsite First Time Assembly (OFTA) in January 2014, less than twelve months after contract signing, and was from the outset designed for hard rock conditions. A Measurement While Drilling (MWD) system was included to analyze the ground conditions ahead of the TBM, while probe drilling was done systematically throughout the project. “This is a strong and simple machine ready to tackle hard rock conditions, but also designed to handle softer rock, which allowed for fast excavation. We had good support from competent Robbins field service,” said Andersson.
After all the obstacles, it was clear that the breakthrough ceremony celebrated a triumph of teamwork as well as a new chapter for TBMs in Norway. “Our whole jobsite was gathered for the event: LNS management, representatives from Robbins, and our client Statkraft. People said it was the best breakthrough event they had seen,” said Andersson. Now that tunneling is complete, project owner Statkraft will work to commission the tunnel and fill it with water by spring 2016.
The News in Brief:
- A 3.5 m (11.5 ft) Robbins Main Beam is a hard rock veteran, with a career spanning 32 years.
- With the 6.3 km (4.0 mi) Mid-Halton Outfall Tunnel under its belt, the Robbins Main Beam will have bored nearly 30 km (18.6 mi) of tunnels.
- The refurbished TBM was beefed up with modern VFDs, electronics, and a modified cutterhead for high-capacity tunneling in hard rock.
- Contractor STRABAG is in charge of tunnel construction in Ontario, Canada, as well as the construction of two deep shafts.
On July 22, 2015, a 3.5 m (11.5 ft) Robbins Main Beam TBM began a new chapter in its storied 32-year career. Originally built for the Terror Lake project in Alaska, the veteran machine has been used all over the world, most recently in Hong Kong. Including its new 6.3 km (4.0 mi) long tunnel for the Mid-Halton Outfall in Ontario, Canada, the machine will have bored nearly 30 km (18.6 mi) of tunnels since 1983.
The machine’s latest endeavor will not be without challenges. The rebuilt TBM has been beefed up for high-capacity tunneling in hard rock. Geology is expected to consist of laminated shale with interbedded limestone and siltstone layers and a maximum rock strength of 120 MPa UCS. “We have kept this a simple, streamlined Main Beam machine, but we modified the cutterhead with larger muck buckets, so material can be moved through it faster,” explained Robbins Project Manager Lynne Stanziale. In addition the TBM was outfitted with fully modernized VFDs, electronics, and high-capacity gearing and motors. The back-up system was also modified to make it more mobile through two 130 m (427 ft) radius curves that the TBM will have to navigate, one in each direction.
“The concept of using refurbished TBMs bears great opportunities for value-for-money constructors,” said Christian Zoller, Commercial Project Manager for contractor STRABAG. “Our TBM “˜Peggie’ is evidence of that–when well-maintained and professionally refurbished, the lifespan of these machines is extensive. We’re pleased to see that our client Halton Region has the forward-oriented mindset that allows STRABAG to provide its renowned high level of skill and quality, paired with the good value for money that a refurbished TBM yields.”
Contractor STRABAG, who has had several projects in Canada including the epic Niagara Tunnel project, is in charge of the works. In addition to the tunnel, STRABAG had to construct two deep shafts for the launch and exit of the TBM. The scheme involves two sections of tunnel designed to carry treated effluent water from a treatment plant in Oakville into Lake Ontario. The completed system will upgrade water treatment capacity in the Halton Region of Ontario.
The TBM was launched from a 12 m (39 ft) diameter, 62 m (203 ft) deep shaft and is ramping up production, having excavated over 300 m by early September 2015. “An ongoing challenge associated with the tunneling on this project is the requirement to drive the TBM downhill for the first 4 km (2.5 mi) of the tunnel. Keeping the water that infiltrates the tunnel from flowing directly to the cutterhead requires significant effort,” said Terry McNulty, Technical Project Manager for STRABAG.
Management of water inflows is not the only challenge. A portion of the drive will curve to run directly under Lake Ontario for 2.1 km (1.3 mi), though the tunnel is deep enough that it will remain in bedrock. Once the machine has completed its final bore under Lake Ontario, it will be backed out of the blind heading and removed from an 8.0 m (26 ft) diameter shaft in a local park.
“We can already see the potential performance that this TBM will have, once fully assembled and tested. We look forward to the continued support and cooperation with our partner Robbins on this endeavor,” said Zoller. Though the TBM has only recently started up, crews are moving forward with a plan to line the tunnel with mesh panels and ring beams if necessary. A cast-in-place liner will follow on after tunneling is completed in August 2017.
The News In Brief:
- A Robbins 3.96 m (13.0 ft) Main Beam TBM launched in spring 2015 to bore Hawaii’s longest tunnel.
- The 4.8 km (3.0 mi) Kaneohe-Kailua Wastewater Conveyance Tunnel is being built for the City and Council of Honolulu to stem overflows of wastewater after rain events.
- Southland/Mole JV is constructing the tunnel””the first of its scope to be built in the Hawaiian Islands.
- As of June 2015, the Robbins TBM had excavated more than 300 m (1,000 ft), and was boring at a rate of 12 to 15 m (40 to 50 ft) per day in basalt rock.
In the spring of 2015 by the idyllic shores of Oahu, a Robbins 3.96 m (13.0 ft) diameter Main Beam TBM began its long journey. The TBM started its excavation on a 4.6 km (2.8 mi) drive for a new sewer tunnel in Kaneohe, Honolulu, Hawaii, USA. The machine, nicknamed Pohakulani, meaning “Rock Girl” in Hawaiian, launched from a 23 m (74 ft) deep starter tunnel on a mission to bore through almost 4.8 km (3.0 mi) of basalt bedrock. Contractor Southland/Mole JV is building the Kaneohe-Kailua Wastewater Conveyance Tunnel for the City and Council of Honolulu, which will improve wastewater infrastructure by eliminating overflows during rain events.
The deep tunnel option was not the first design considered for the project: preliminary plans called for a smaller tunnel traveling under the bay. As Kaneohe Bay is an environmentally-sensitive area, a deep tunnel remained an attractive option. Richard Harada, of project consultant Wilson Okamoto Corporation, explains the ultimate decision: “A number of factors were considered in making the decision to build a deep tunnel including reliability, construction costs, life cycle costs, environmental impacts, constructability and qualified contractor availability.”
During the tunnel design phase, it was decided that the tunnel route should travel inland and deeper underground in order to bypass one of the few residential areas along the alignment. Designers introduced an isolated curve in the tunnel alignment of 150 m (500 ft) radius, requiring the TBM to be designed with a unique back-up system. There will also be operational procedures when crews navigate the tunnel curve, requiring the machine to be operated using half strokes rather than a full TBM stroke.
The curve is not the only unusual aspect of the tunnel; in fact, a tunnel on this scale has not been built in the Hawaiian Islands before. Everything from the logistics of the tunnel operation to pre-grouting sections ahead of the TBM for groundwater control are new to the Aloha State. Director of Southland, Tim Winn, elaborates: “There has not been a Tunnel Boring Machine of this size in the Hawaiian Islands or a tunnel of this length. The tunnel is being driven from an active Water Treatment Plant (WTP), and space is at a premium. There are also simultaneous contracts being performed there outside the scope of our work.” He adds that although there have been challenges, teamwork has been key: “Robbins Field Service has been extremely valuable during assembly and commissioning of the TBM.” As of June 2015, the TBM has excavated more than 300 m (1,000 ft), and is boring at a rate of 12 to 15 m (40 to 50 ft) per day in basalt rock. Rock bolts, steel arches, wire mesh, and ring beams are being installed as necessary.
Upon completion, the deep tunnel will enhance water treatment capabilities and further aid in ceasing non-compliant, uncontrolled or moderately treated wastewater discharges. The Main Beam TBM is estimated to end its journey in eight to ten months at the Kaneohe Wastewater Pre-Treatment Facility.
The News In Brief:
- The Robbins Remote Controlled Small Boring Unit (SBU-RC) is a new type of boring machine capable of excavating small diameter hard rock tunnels at long distances, on line and grade.
- The SBU-RC is currently manufactured in the 36-inch (900 mm) diameter range, but could be designed as small as 30 inches (750 mm) in diameter.
- The SBU-RC features a smart guidance system for pinpoint steering accuracy and is controlled from an operator’s station on the surface.
- Muck removal is accomplished through a vacuum system, making the Robbins SBU-RC more cost effective than MTBMs requiring slurry and cleaning plants onsite.
- A Robbins 36-inch (900 mm) SBU-RC completed a critical hard rock crossing below railroad tracks two weeks early in Bend, Oregon, USA, breaking through on May 5, 2015.
- The SBU-RC holed through on line and grade after achieving up to 50 ft (15 m) of advance per day in abrasive basalt rock up to 7,000 psi (48 MPa) UCS
In Bend, Oregon, USA, local contractor Stadeli Boring & Tunneling had a unique set of circumstances for a new gravity sewer interceptor. “We had a contract with general contractor Taylor NW to furnish and install 323 ft (98 m) of 36-inch (900 mm) steel casing under railroad tracks. Line and grade were very crucial, and the tolerances were very close. We had to be right on,” said Larry Stadeli, president and owner of Stadeli Boring & Tunneling. In addition to those parameters, the job was also in solid rock.
Fortunately, there was a solution available to help them. The contractor turned to The Robbins Company, a business that they had worked with many times over the years for their Small Boring Units (SBUs). Stadeli first contacted Robbins 10 years ago to rent a 30-inch standard Small Boring Unit (SBU-A), and has since rented dozens more. The company currently owns two SBU-As, but their Bend, Oregon job required precision guidance systems that their SBU-As lacked. “We met with Robbins in Ohio and told them what our needs were. They felt like their 36-inch (900 mm) prototype machine, which they had tested at one other job in Oman, would be a good fit. They listened to what we were wanting and needing to have done,” said Stadeli.
At Robbins, Kenny Clever, SBU Sales Manager, and a group of engineers were honing the prototype machine that fit the bill. Known as the SBU-RC, for Remote Controlled Small Boring Unit, the machine was equipped with a smart guidance system by TACS. The guidance system could show an operator projections of the future bore path so steering corrections could be made before the machine was ever out of line and grade. The feature was critical for the crossing below the railroad tracks, which could not be shut down if problems occurred.
The SBU-RC is currently manufactured in the 36-inch (900 mm) diameter range, but could be designed as small as 30 inches (750 mm). The machine operates much like a Motorized SBU (SBU-M) with a circular cutterhead and cutting tools that can excavate hard rock or mixed ground conditions. An in-shield drive motor provides torque to the cutterhead, while a pipe jacking system or Auger Boring Machine (ABM) provides thrust. Clever explains the biggest differences: “There is no manned entry. It eliminates the human element, so it is safer and there is no need for ventilation and other things required when you have a worker in the tunnel. With its guidance system, it also eliminates much of the risk on line-and-grade-critical bores.” Muck removal is accomplished via a vacuum system connected to a vacuum truck. The machine is capable of excavating hard rock and mixed ground crossings up to 500 ft (150 m) long, depending on conditions.
While microtunneling machines have been used on jobs such as these, Clever cites key advantages for the SBU-RC: “There is no slurry to mix or contend with. With MTBMs the slurry must be cleaned, pumped, and treated. With the SBU-RC there is a clean and dry pit, with no spoils to remove. The way the SBU-RC operates is much more cost effective. The SBU-RC is also available for lease; MTBMs are often not cost effective to lease for contractors trying to stay competitive.
The SBU-RC was delivered on April 14, 2015, and was lowered into a launch pit 26 ft (8 m) deep. There were several early tweaks to the setup including a larger vacuum truck that improved suction, and some modifications to the cutterhead including grill bars. These modifications were expected and will be incorporated into later versions of the machine.
The machine began boring in volcanic basalt rock that was full of fissures, fractures, and rubble pockets between 5,000 and 7,000 psi (34 to 48 MPa) UCS. While the start-up was rough going, crews quickly began getting rates of 20 ft (6 m) per day. “As we got used to the machine we went up to 40 ft (12 m), and one day we even got 50 ft (15 m). We were able to cut off a couple weeks of our schedule time. Taylor NW was very pleased about it. When you look down the pipe now after it’s finished, it looks like a rifle barrel. There is no sag, it’s all in one straight line,” said Stadeli.
The early completion by the SBU-RC delighted the City of Bend and all those involved. “I think the SBU-RC is an exciting piece of equipment that has been compressed into a 36-inch size. To make it all work it is very compact. It’s impressive that the components have been sized down and it still works so efficiently,” said Stadeli.
With the clear success in Oregon, Robbins is looking to lease the machine on more projects and expand their offerings. As Clever put it: “Finally our industry has provided a small diameter, on-line-and-grade machine that will drill in solid rock at distance. This is a game changer, it will be the most innovative piece of equipment in our industry for a long time.”
The News In Brief:
- The Robbins 6.2 m (20.2ft) diameter Main Beam TBM completed the Eagle Creek extension tunnel on March 5, 2015.
- The world-record-setting jobsite includes a number of unique aspects, the conveyor system being one of them. The Robbins continuous conveyor consists of 82,000 ft of belt and travels through two unprecedented 90-degree curves.
- The project was put in place to reduce the amount of raw sewage overflows in the city’s neighborhoods and clean up tributaries along the White River.
On March 5, 2015, a Robbins 6.2 m (20.2 ft) diameter Main Beam TBM finished boring a 2.8 km (9,175 ft) long extension tunnel, known as the Eagle Creek Tunnel, for the Indianapolis Deep Tunnel System in Indiana, USA. The contractor, Shea/Kiewit (S-K) JV, had much to celebrate: “I’m proud of our world records, and most of all our men and the hard work they have done as a team, working together to accomplish a project of this size,” explained Stuart Lipofsky, Project Manager, for S-K JV. “We finished the first 12.5 km (41,000 ft) [of the main tunnel] almost a year ahead of schedule. The extension added time but what is remarkable is that we were still able to finish within the original contractual dates,” continued Lipofsky. The completion of the first leg of a much larger tunnel system targets three critical CSOs that flow into the nearby White River, and will go online in 2017. The completed tunnels bring the city one step closer to achieving its consent decree with the U.S. Environmental Protection Agency (EPA), set to be achieved by 2025, to eliminate overflows into the city’s rivers.
The rebuilt Robbins hard rock TBM was first used on the 12.5 km (7.8 mi) long main tunnel, called the Deep Rock Tunnel Connector (DRTC). The new cutterhead arrived onsite in November 2012, and the machine was launched from a 76 m (250 ft) deep shaft to bore through limestone and dolomite. The TBM achieved world records in its size class of 6 to 7 m (20 to 23 ft), including “Most Feet Mined in One Day” (124.9 m/409.8 ft); “Most Feet Mined in One Week” (515.1 m/1,690 ft); and “Most Feet Mined in One Month” (1,754 m/5,755 ft). According to Tim Shutters, Construction Supervisor for project owner Citizens Energy Group, there were two main factors for the TBM’s high performance: “The first one is the very nice cutterhead provided by Robbins. It has performed very well. [Second], rock conditions are favorable for mining operations and optimal for fast production.”
Another important element that helped the speedy machine achieve a fast advance was, as Lipofsky put it, “one of the most complex continuous conveyor systems in North American tunneling construction.” The custom-built Robbins system, consisting of 25 km (82,000 ft) of belt, included horizontal and vertical conveyors for efficient muck removal. The system was the first built by Robbins to go through such sharp curves: “The belt is going through two 90-degree curves in opposite directions and S-curves in other places. It’s very unusual and amazing to see a belt system perform as well as this one did,” said Lipofsky.
Once complete, the deep tunnel project will reduce the amount of raw sewage overflows and clean up tributaries along the White River. Tim Shutters describes the environmental benefits the project will provide the Indianapolis community: “I’ve lived in Indy all of my life, and the White River has never been a focal point for the city as there is a lot of pollution. I really think that once it has been cleaned up, people will want to visit, they will swim and fish, and property values along that body of water will go up. Being able to finally utilize the river is key for us.”
After the early completion of the Eagle Creek Tunnel, the project will be moving into its next two tunneling phases. The White River Deep Tunnel will continue 8.5 km (5.3 mi) north of the completed DRTC and pump station. The Lower Pogues Run Deep Tunnel will split off 2.7 km (1.7 mi) from the White River Deep Tunnel heading east. Two additional tunnels, including Fall Creek and Pleasant Run, are anticipated to be built in 2020, and the project (27 km/17mi of tunnels in total) is expected to be fully completed by the end of 2025.
Robbins proudly announces its Crossover Series of TBMs, a line of field-tested, rugged Dual Mode-type machines. Crossover TBMs feature aspects of two TBM types, and are ideal for mixed ground conditions that might otherwise require multiple tunneling machines. The XRE (standing for Crossover Rock /EPB) is the most common type of hybrid machine, and features characteristics of Single Shield Hard Rock machines and EPBs for efficient excavation in mixed soils with rock.
An XRE TBM recently completed tunneling at Australia’s Grosvenor Decline Tunnel, where it excavated two mine access drives at rates fourteen times faster than a traditional roadheader. The latest drive was completed on February 9, 2015. “This was a big step forward for the mine to appropriately use civil tunneling technology for a mining application. I take my hat off to the management of owner Anglo American Coal to have the foresight and leadership ability to take this step. Using the Crossover technology [versus the traditionally-used roadheader method], the project was finished on schedule,” said Lok Home, Robbins President.
Additional types of Crossover machines include the XSE (Crossover between Slurry/EPB) and the XRS (Crossover between Rock/Slurry) TBMs. The Crossover series is quickly gaining in popularity, with Robbins Crossover TBMs currently being assembled in Mexico, Turkey, and Azerbaijan. An XRE TBM will begin excavation for Mexico’s TÃºnel Emisor Poniente II (TEP II) later this year, while an XSE is being readied for excavation at the Baku Metro.
The rebranding and Crossover terminology embodies the concept that the machines are able to cross over between modes, says Home. The unique machines are a top focus point for the company: “Robbins comes at this business with extensive rock experience so everything we design comes with the assumption that there will be tough conditions. When you have to “cross over” to another mode then already you are in difficult conditions, and contractors need robust machines to get through these challenges,” says Home.
Home foresees that machine sales will grow as more projects worldwide are planned in difficult and varying ground conditions. Survey results back up the trend, indicating an increased interest in Crossover-type machines worldwide. “This is a continuous evolution and we are consistently endeavoring to improve Crossover designs. We have three of the machines in production now and I see this number increasing year by year as the industry sees and accepts their value.”
The News in Brief:
- The Grosvenor Decline tunnel marks the first method of a TBM being used in a coal mine in Queensland.
- The unique Crossover Rock/EPB TBM features design aspects from both hard rock Single Shield and soft ground EPB TBMs to bore through a variety of ground.
- The “Crossover” designation is new for Robbins, and will going forward be the designation for all types of Dual Mode TBMs.
- The Crossover TBM for Grosvenor was uniquely designed for excavation in conditions that included the potential for methane gas. It was designed as Class 1, Division 2 Coal Mine Compliant.
- The TBM excavated at rates fourteen times that of a traditional roadheader operation (70 m per week on average vs. 5 m per week).
- The TBM broke through into an active section of the coal mine on February 9, 2015, completing excavation of two mine access tunnels.
Full Press Release:
A ground-breaking TBM brought a mining operation one step closer to first coal on February 9, 2015. The Robbins Dual Mode “Crossover” Rock/EPB TBM completed tunneling at Anglo American’s Grosvenor Project in Queensland, Australia. The “Crossover” designation is new for Robbins Dual Mode TBMs, and will be used for all such projects going forward. The efficient type of TBM used at Grosvenor is now known as an XRE, standing for Crossover between Rock/EPB. Other types of machines are designated the XSE (Crossover between Slurry/EPB) and the XRS (Crossover between Rock/Slurry).
The Grosvenor Mine, a Greenfield coal operation, was the first to utilize TBM technology for mining tunnels in Queensland. Mine owner Anglo American Coal chose the 8.0 m (26.2 ft) machine for two decline access tunnels at grades of 1:6 and 1:8, one for conveyors and another for people and equipment.
The XRE TBM was picked over the traditionally-used roadheader method for several reasons, including excavation speed and tunnel maintenance. The choice proved prescient with the machine excavating at a rate approximately ten to fourteen times faster than a roadheader™bout 70 m per week for the TBM vs. 5 m per week for a roadheader. In addition, the final tunnels have a smooth profile and are segment-lined, requiring minimal upkeep during the planned 40-year life of the mine. “In the coal mining community, and certainly in Queensland, companies are aware of the Grosvenor project and how it has set a benchmark for underground access drift construction,” said Glen Maynard, Robbins Field Service Site Supervisor at Grosvenor.
The machine’s Crossover capabilities enabled it to operate in both hard rock and mixed ground. In addition, the TBM was required to operate during gaseous conditions. The unique TBM design included a cutterhead capable of interchanging hard rock and soft ground cutting tools, a two-stage center-mounted screw conveyor, a “quick removal” shield system, and flame-proof machine components due to the possibility of methane gas in the underground environment.
The TBM was optimized for hard rock and mixed ground excavation in geology ranging from soft clay and soil to sandstone and basalt. The two-stage screw conveyor worked in both ground conditions to draw muck from the tunnel face. Two sets of shields were built for the TBM’s “Quick Removal” system, and were detached from the machine at the end of each blind tunnel to be left in the ground for constant support, a requirement in Australian tunnels. The inner core components of the TBM were then retracted out of the segment-lined tunnels on specially designed transport dollies.
The machine began boring the conveyor tunnel in December 2013, and after completion in May 2014 was successfully retracted and transported to the second tunnel site. The machine was then re-commissioned for the people and equipment tunnel in November 2014 with a new set of shields. Once excavation commenced, boring was completed in 88 days at an average of 10.9 m per day, with a best day of 25.2 m. The bore itself was similar to the first, with few challenges encountered other than elevated methane gas levels that required several temporary stoppages in order to safely remove the gas from the tunnel. “The machine performed very well and had high reliability. The cutting tools, in particular the knife edge bits, were exceptional. The bits were required for most of the drive and one complete set lasted 650 meters,” said Maynard.
The team is now preparing the machine for its final retraction and roll-out, and it will be on the surface in less than two months. The TBM will then be stored onsite for future Anglo American mining projects.
Once the longwall mine is operational in 2016, Grosvenor is expected to produce five million tonnes of coal per year over the next 26 years.
The News In Brief:
- Breaking through on January 28, 2015, the rebuilt EPB at NYC’s Harbor Siphons tunnel overcame obstacles including flooding, extensive rebuild work, and difficult ground.
- The CAT-manufactured machine was fully submerged by Superstorm Sandy in October 2012 and became severely corroded by saltwater.
- Contractor Tully/OHL USA JV hired Robbins to rebuild and refurbish the machine, including all electrical components and an all-new PLC.
- The Robbins rebuild took four months and the machine was re-launched in April 2014.
- Robbins remained onsite to assist in continuing challenges including high water pressure and glacial geology.
- Despite the gamut of obstacles thrown at the machine, crews were able to achieve up to 30.48 m per day and 25 rings in 24 hours.
On January 28, 2015, about 35 m (115 ft) below New York Bay, a celebration was underway. Workers from the local tunnelers union in New York City, USA, known as the Sandhogs, completed the last meters of tunnel alongside workers for subcontractor Tully/OHL and Robbins field service. The team had many reasons to celebrate””not only had their TBM just completed a much-needed undersea tunnel, but it had also done so after a near-catastrophic natural disaster, extensive rebuild and geologic complications.
The New York City Harbor Siphons Project began simply enough””the 2.9 km (1.8 mi) long tunnel between Brooklyn and Staten Island was designed to replace two existing shallow water lines below the bay. The project, managed by the New York City Economic Development Corporation (NYCEDC), replaces the lines with the deeper siphon in order to make way for a larger project””the dredging of the Anchorage Channel. The channel (part of New York Bay) is an important waterway for shipping, and its dredging will allow for mega ships carrying large cargo loads to pass through.
Tully/OHL USA JV procured a 3.8 m (12.5 ft) diameter EPB TBM from Caterpillar in 2012. The TBM, dubbed “Pat”, was designed to drive through highly variable clays, sands, weathered rock and boulders. It was launched from the 35 m (115 ft) deep Staten Island shaft, boring towards the 40 m (131 ft) deep Brooklyn shaft, in August 2012.
In October 2012, the unexpected happened: a massive hurricane, dubbed Superstorm Sandy, barreled down on the U.S. East Coast with winds up to 145 kph (90 mph). Extreme flooding at the waterfront jobsite in Staten Island overtopped protective concrete barriers that had been designed three feet above the 100-year flood level. Seawater rushed into the tunnel and the nearly 113 m (370 ft) long machine was entirely submerged only 460 m (1,500 ft) into its drive. “Obviously this was our biggest challenge,” said Luis Alonso, Tunnel Manager for OHL. “After that, not many people thought we would be able to finish this tunnel.”
After floodwaters began to recede, OHL set about determining the extent of damage on the machine. The TBM was severely corroded by saltwater and sat idle until July 2013. During that time, CAT announced its impending closure of its TBM business, and the contractor looked to other manufacturers. “OHL was always determined to finish this project. After studying other options, we decided to proceed with the full refurbishment of the TBM with the help of The Robbins Company. The whole crew worked together to achieve that goal,” said Alonso.
Robbins coordinated the effort to replace corroded hydraulic components and all new electrical systems in mid-December 2013. Electrical systems had to be reverse-engineered, while the PLC had to be entirely redesigned. The refurbishment also centered on removing the rear eleven gantries and belt conveyor to be cleaned, evaluated and repaired. The rebuild took about four months, much of it done in the tunnel under water pressure, and crews were able to return to mining on April 14, 2014.
To ensure that the project stayed on the incline to success, Robbins Field Service personnel remained onsite to support ongoing maintenance of the TBM. With their help, machine performance steadily increased, eventually reaching rates as high as 30.48 m (100 ft) per day and as much as 25 rings in 24 hours in August 2014.
As excavation picked up, ground conditions changed from marine sediments (clay, silt and sand) to glacial geology with sand, exceptionally hard boulders, and excessive water ingress, resulting in slow propulsion rates. “The TBM needed more thrust and we decided to implement four additional auxiliary cylinders. Robbins field service helped in developing the size, features and location of the cylinders, which were eventually placed in the lower quadrant of the propulsion system,” said Alonso. With the new system crews were able to re-establish forward progress. The constant hurdles continued into early October when a hyperbaric intervention at 4 bar of pressure was required to change the cutting tools in a pocket of glacial soils. Despite the new obstacles, the crew was able to steadily increase the rate of excavation to 5 to 7 rings per day. “This tunnel is an important part of a larger project, and we are proud to be doing what we do every day, dealing with troubles as they come up, until we reach the end of the drive,” said Alonso. Now that tunneling is complete, the stationary and tail shields will be buried at the exit shaft entrance, with the cutterhead and back-up being removed.
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