Author: Robbins

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.

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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 100^th 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 100^th 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 20^th 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.”

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Robbins Double Shield Takes on Nepal’s First TBM Project for Bheri Babai

Nepal will welcome its first TBM ever this summer, a 5.06 m (16.6 ft) diameter Double Shield machine for the Bheri Babai Diversion Multipurpose Project (BBDMP). The Robbins TBM underwent its Factory Acceptance Testing in July 2017 and is currently being shipped to the jobsite in the Siwalik Range, part of the Southern Himalayan Mountains. Pre-construction, including laying gravel onto rural roads and excavating wells for drinking water, has been completed to make way for the TBM and its impending launch.

The BBDMP is one of Nepal’s 11 National Pride Projects–prioritized plans sanctioned by the Government of Nepal to further develop the mainly rural country. This project will irrigate 60,000 hectares (almost 15,000 acres) of land in the southern region of Nepal, benefitting an estimated 30,000 households. It will divert 40 cubic meters of water (1,400 cubic feet) per second from Bheri River to Babai River under a head of 150 m (492 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.

Contractor China Overseas Engineering Group Co. Ltd. Nepal Branch (COVEC Nepal Branch) is responsible for the headrace tunnel and is aware of the challenges associated with tunneling in tough geology. “The design of Robbins TBMs is good, and in particular Double Shield TBMs,” said Project Manager of BBDMP, Hu Tianran. The Siwalik range is projected to consist of mainly sandstone, mudstone and conglomerate, requiring a TBM that can withstand squeezing ground, rock instability, possibly high ingress of water and fault zones. Maximum cover above the tunnel is 820 m (0.5 mi).

Due to the challenges in the young geology of the Himalayas, Difficult Ground Solutions (DGS) have been incorporated into the machine’s design. A stepped shield has been designed to move through squeezing ground. Robbins Project Engineer Missy Isaman talked about the DGS features incorporated into the TBM: “There is a probe drill in the rear that probes through the gripper shield in 14 places. We added ports in the forward shield for drilling too. There are eight ports around the circumference for hand drilling. There are also six ports in the top 100 degrees of the shield for forepoling.” She further noted that no equipment was ordered for either of the forward shield drilling options, but it’s easier to add the ports to the shield now, in case more comprehensive drilling is needed later in the bore. Other machine modifications included 35 mm (70 mm on the diameter) of possible overcut for gage cutters, and additional ports in the forward shield for dewatering.

Muck removal will be achieved by muck cars. Robbins will provide Field Service to support the machine erection, testing, commissioning and boring of the first 500 m (1,640 ft). The tunnel will be lined with hexagonal precast concrete segments.

The project owner, the Government of Nepal’s Ministry of Irrigation (MOI), has chosen a TBM over the traditional method of Drill & Blast due to the faster mobilization and rate of advance offered by mechanized mining. “The reason a TBM was chosen for this project was because using D&B method could have taken at least 12 years for project completion. This was due to there only being one excavation heading with no possibility of launching multiple operations using adit tunnels,” said Robbins General Manager for Nepal, Prajwal Man Shrestha. More generally, Mr. Shrestha saw the project as a way to prove that TBMs can indeed take on complex Himalayan rock. “Since the Himalayan range has a young geology and not much has been surveyed yet, the use of newer technology is looked upon with slight apprehension. The first few TBM projects and additional surveys will show how suitable TBM technology will be for the Himalayan Range.”

The success of the BBDMP, a national pride project, is paramount for the country as well as the TBM industry. It is expected to help aide the food crisis in the mid-western region of Nepal by increasing agricultural yields and invigorating socio-economic development in the region. The Robbins TBM for the 12.2 km (7.5 mi) tunnel is scheduled to launch in November 2017.

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SBU-RC Spec Sheet

The SBU-RC is a game-changer for the trenchless industry, making long, line-and-grade-sensitive crossings possible at small diameter. The SBU-RC is an unmanned, articulated mixed ground and hard rock boring machine for use with standard Auger Boring Machines (ABMs) or pipe jacking systems.

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Continuous Conveyor Spec Sheet

Robbins’ continuously advancing conveyors are designed to increase the efficiency of muck removal and vastly simplify tunneling logistics. Robbins Continuous Conveyors have been successfully employed on nearly 100 projects worldwide—more than any other TBM tunnel conveyor manufacturer.

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Robbins: Focused Forward

Robbins has been the foremost manufacturer of Tunnel Boring Machines and underground construction equipment for nearly 70 years. Journey through the company history as told by Robbins employees, and hear about the latest innovations and design concepts that make Robbins a thought-leader in the industry.

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Robbins TBM “Rosie” is First Crossover TBM in the U.S.

A Robbins Crossover (XRE) TBM measuring 9.26 m (30.4 ft) in diameter underwent factory acceptance on May 30, 2017. The gargantuan machine was initially unveiled at Robbins’ Solon, Ohio headquarters during a press day on May 25 before being shipped 40 km (25 mi) south for construction of the Ohio Canal Interceptor Tunnel (OCIT) in Akron. Those present included Akron Mayor Daniel Horrigan, Robbins chief engineer Dennis Ofiara, and David Chastka, project engineer for contractor Kenny-Obayashi JV.

The TBM, which includes features of both EPB and Hard Rock Single Shield TBM types, is the first Crossover machine to be used in the United States. It will be launched from a 12 m (40 ft) deep portal site and build the first 68 m (226 ft) in soft ground, transitioning to a 183 m (600 ft) long zone of partial face shale before switching to hard-rock mode for the remainder of the drive in full face shale. Probe drilling will be done continuously using two probe drills to determine which mode the TBM should be in. “Robbins has provided a robust design that we are confident will be able to handle all of the challenges of the OCIT Project tunnel drive,” said Chastka.

Unique aspects of the machine include a versatile cutterhead that will be configured with consideration for both the short soft ground section and the longer section (about 65% of the tunnel) in hard rock. A combination of disc cutters and sacrificial rippers will be used in case a cutter becomes blocked.  The required rolling torque of the disc cutters has been reduced by 25% to encourage smooth rotation in soft ground. The motors of the XRE machine have been reworked from an original EPB configuration to permit higher motor speed at reduced torque for the open mode segments of the drive.

Muck removal will be achieved with a durable screw conveyor, the first flight of which is covered welded-in wear plates. The auger shaft is lined with hard facing in a crosshatch pattern, while the screw conveyor casing has been similarly lined in wear plates and hard facing.  A wear monitoring plan has been prepared for the entire drive in order to maximize efficiency in the section of more abrasive rock. Robbins Project Manager Pablo Salazar is proud of the utilization of local jobs during the TBM construction and design process: “We have built good portion of the machine in the northeast Ohio area. Many components were fabricated locally with sub-suppliers, as well as in our own shop.”

The machine was dubbed “Rosie” in honor of Rosie the Riveter, an icon representing the American women who worked in factories and shipyards during World War II. Hundreds of “Rosies” including Akron resident Rose May Jacob worked in factories to turn out materials and armaments for the Allied war effort. The TBM will be shipped in truckloads to the jobsite, with the large cutterhead shipped in four pieces. “The entire process of assembly has allowed to the contractor to follow very closely through the testing of the machine, so they are very familiar with the TBM at this point. At the jobsite, we will also provide immediate support for both spare parts and personnel,” said Salazar. Jobsite supervisors from Robbins will assist in TBM assembly and excavation for at least the first 1,000 m (3,280 ft) of boring.  Tunnel boring is scheduled to begin in August of this year.

The OCIT Project for the City of Akron 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.  The consent decree specifies that the tunnel must be operational by December 31, 2018.

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Crossover XSE Spec Sheet

If the geology of your project includes high permeability soils combined with sections of low permeability ground, the Crossover XSE is the solution for you. Not all projects fit within the parameters of specific TBM types, and at Robbins we believe that your machine should be custom-engineered for your unique project requirements. That’s where the Crossover Series of TBMs comes in.

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Crossover XRE Spec Sheet

Whether the geology of your project includes sections of hard rock, soft ground, boulders, or a little bit of everything, Robbins has a solution for you. Not all projects fit within the parameters of specific TBM types, and at Robbins we believe that your machine should be custom-engineered for your unique project requirements. The XRE TBM offers the best features of both EPB and Hard Rock Single Shield TBMs.

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Main Beam TBM Spec Sheet

Robbins Main Beam machines feature High Performance (HP) options including large diameter cutters, variable frequency electric drive motors, and adaptable ground support systems. Their design consists of a rotating cutterhead that holds disc cutters (ranging from 17 inches to 20 inches in diameter), which are positioned for optimal boring.

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