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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.
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.
Mexico City’s Record-Breaking Crossover TBM Makes Final Breakthrough
On June 8, 2017, a select group of project officials, including Mexico’s President Enrique Peña Nieto, celebrated the final breakthrough of an epic tunneling project. The 8.7 m (28.5 ft) diameter Robbins Crossover TBM is the first such hybrid machine to operate in North America, and it completed the Túnel Emisor Poniente (TEP) II on a high note. The TBM, known as an XRE—a Crossover (X) between Rock (R) and EPB (E) TBMs—navigated fault zones, variable ground, low cover, and more to achieve a national record of 57 m (187 ft) in one day as well as maximum rates of 231 m (758 ft) in one week and 702 m (2,303 ft) in one month.
“The XRE has a great advantage as it is designed to work in open and/or closed mode (EPB); allowing it to excavate the tunnel either in soil or in rock. We’ve verified that its performance was very efficient,” said Ing. Juan Alberto Herrera Moro y Castillo, TEP II Section Chief for owner CONAGUA, Mexico’s National Water Commission.
The unique machine and its Robbins continuous conveyor system were built on location using Onsite First Time Assembly (OFTA), and designed for a contractor consortium of Aldesem, Proacon, and Recsa. The Robbins XRE TBM featured components like a convertible cutterhead with interchangeable cutting tools, interchangeable TBM belt conveyor and screw conveyor, and multi-speed gearboxes to increase torque for tunneling through difficult ground. “The benefits of the design are in its exceptional thrust power and in the ease of changing the cutterhead torque. This makes the process much easier should the machine become stuck in difficult ground,” said Alberto Martinez, head of the tunneling department for RECSA.
The XRE machine was launched in August 2015 to bore the 5.8 km (3.6 mi) long wastewater tunnel. The machine was set up in a hard rock configuration and mounted with 20-inch diameter disc cutters. Early in 2016 the TBM hit the first of several contact zones, a 30 m (98.4 ft) wide fault of fractured and blocky rock. While the excavation through the contact zone was slow going, progress picked up again in the more competent andesite rock. After an intermediate breakthrough in March 2016 into an 80 m (262.5 ft) deep shaft followed by inspection and maintenance, the TBM continued on.
While boring in fractured andesite rock in autumn 2016, the TBM encountered a naturally occurring cavern believed to be the result of either a rock fall in a transition zone, or an old, underground lake body that had eroded the rock away. The cavern was estimated at 90 cubic meters (3,200 cubic ft) in size, including about 57 cubic meters (2,010 cubic ft) of unstable floor area. The TBM was stopped and immediate measures were taken to stabilize the ground in front of the machine with polyurethane foam before filling the cavern with a mixture of pea gravel and grout.
By the end of October 2016, the TBM had reached a final 900 m (2,950 ft) long section of soft ground, where it was converted to EPB mode. In this final reach of tunnel with low cover, the distance from the top of the tunnel to residential home foundations was as low as 4 m (13 ft), and the ground had the consistency of reconsolidated soil. In order to stabilize the soft soils and minimize the risk of settlement below the residential area, the tunneling crew drilled from the surface and installed 890 micro-piles at 1.0 m (3.3 ft) intervals. “We were able to do this without causing damage to property owned by neighbors in the zone bordering the path of TEP II, or to the road or the urban infrastructure installed in that area,” explained Ing. Francisco Miguel Lopez, Jobsite Manager TEP II for contractor Aldesa.
Now that tunneling is complete, the tunnel will receive a secondary concrete lining of 35 cm (14 in) thickness before going into service. The wastewater tunnel will overhaul the current system in western areas outside of Mexico City and serve to prevent recurrent flooding in Valle Dorado. In particular, the tunnel will benefit the cities of Cuautital Izcalli, Tlalnepantla, and Atizapan de Zaragoza, which altogether are home to 2.1 million inhabitants.
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.
Robbins Celebrates Tough Tunnels for Clean Energy
In April 2017, a ceremony was held to celebrate the commissioning of the Dariali Hydropower Project in the Republic of Georgia. Many attended the ceremony marking the first carbon-neutral hydropower project in the world, including Georgian Prime Minister, Giorgi Kvirikashvili. The power station, an independent power project (IPP) developed through Dariali Energy Ltd, was a joint venture involving three other firms: Georgian private companies Peri Ltd and Energy LLC, and state-owned Georgian Energy Development Fund (GEDF). The Dariali HPP gathers water from the Tergi River and directs it through the headrace tunnel to the power house located near the Russian—Georgian border. Each year, the site will generate 500 GWhs of carbon-neutral energy, with 70 percent of power production occurring during the country’s summer months.
Robbins also invested in the project by gaining equity through supplying tunneling equipment and services in consortium with contractor Peri. “Robbins understood the risk in the tunneling portion of the project and we were compensated for taking on part of the risk. Peri is a long-time customer, as we supplied a TBM to them 15 years ago for a small project in Georgia. It was great to be invited to invest and risk share on this project, and to work together again,” said Robbins President Lok Home. The 5 km (3 mi) long headrace tunnel for the power station was bored with the use of a 5.5 m (18 ft) diameter Robbins Main Beam TBM starting in February 2012.
Due to the remote and mountainous location of the jobsite 160 km (100 mi) from the capital Tbilisi, the machine was shipped in pieces to contractor Peri’s workshop, where they were refurbished under Robbins supervision and then delivered to the site to be assembled. Each piece was transported by truck down narrow, winding roads that eventually gave way to dirt paths. Assembly at the jobsite was difficult, as the project site at a 1,700 m (1.0 mi) altitude was blanketed in snow and components arrived in December. Bone-chilling temperatures often reached negative 15 degrees Celsius (5ºF), and 40 below with the wind chill factor. Once the machine had launched, it encountered difficult ground including slate, sandstone, limestone and malms with fault zones.
“The main challenges we faced were boring the tunnel at a 6 percent incline and having restricted access to service the machine. There were also two major landslides that delayed the project for over a year,” said Home. After the first landslide, the access tunnel, which had allowed mud and water to enter the power station, had to be relocated at a higher elevation and facing away from the river valley. When the machine was nearing the end of its bore, a second landslide blocked the exit portal for the machine as well as access to the main highway. Despite these challenges, tunneling crews persevered and the machine successfully holed through in October 2014.
Throughout the construction process, careful steps were taken to minimize the carbon footprint. Although the plant’s energy production is carbon emission free, construction of the plant was not. To offset these emissions, 7,000 seedlings are being planted all around the area in a reforestation effort. In years to come, the trees will absorb enough carbon dioxide to compensate for the emissions produced during the construction of the hydropower plant.
Overall, said Home, there is much to celebrate as the project has immense benefits: “Not only does it provide affordable electrical power for the country with essentially no pollution effects, but it also provided jobs during construction and will continue providing jobs during its operation and maintenance.”
Robbins TBM Takes on Eighth Bore for Galerie des Janots Project
A Robbins TBM, recently christened “Augustine”, is being commissioned to undertake its eighth bore after being launched by contractor Eiffage Civil Engineering on March 3. The TBM, which was extensively modernized and upgraded during the rebuild for the Galerie des Janots project in La Ciotat, France, has previously completed seven other successful projects across Europe and Hong Kong. This time, it will bore the Janots gallery to improve access to water in the communities east of the Aix-Marseille-Provence metropolis (Cassis, Roquefort-la-Bédoule, La Ciotat and Ceyreste). “It’s a single machine 3.5 meters (11.5 ft) in diameter, 250 metric tons (275 US tons), and 135 meters (443 ft) long, that will work 24 hours a day for almost 10 months during this operation,” says Marc Dhiersat, Project Director of Galerie des Janots for Eiffage.
Currently, the machine is ramping up as back-up decks are being installed. As of April 2017, the machine has bored more than 51 m (167 ft), mainly encountering limestone. “Limestone is a rock easy to dig, but one can be confronted with the phenomenon of karst,” explains Loïc Thévenot, Director of Underground Works for Eiffage. “For this purpose, the tunnel boring machine is equipped with a probe drill. If the karst is small, we will fill it with concrete. If it is large, we will erect a small parallel gallery.”
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, water agency Rhône Mediterranean Corsica, and the State Government. The future Janots gallery will replace existing pipelines currently located in the railway tunnel that have significant safety and vulnerability deficiencies with estimated water losses of 500,000 cubic meters (132 million gallons) per year. According to Danielle Milon, Mayor of Cassis, “This is an investment of 55 million euros (USD $59 million) with 11 million in aid from the water agency. This project required 10 years of reflection and work to improve water supply. And water is essential for the development of each municipality, and for citizens’ well-being.”
Augustine is boring a tunnel 2,750 m (1.7 mi) long, and 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 increase to 440 liters (116 gallons) per second,” says Dhiersat. Once the project is complete, networks can easily be maintained in comparison to the old pipes currently running beneath the railway.
Robbins Single Shield to repair a Part of World’s Longest Tunnel
Robbins has completed the manufacture and testing of a unique tunnel boring machine that will be used to repair the longest continuous tunnel in the world. The TBM will be used to overhaul a section of New York City’s Delaware Aqueduct, a 137 km (85 mi) long tunnel that delivers about 50 percent of the City’s drinking water each day. Over the span of two days in February, representatives from the owner New York Department of Environmental Protection (NYDEP), consultant McMillen Jacobs (MJ), and JV contractor Kiewit-Shea Constructors (KSC) traveled to the Robbins facility in Solon, Ohio to witness the Factory Acceptance Testing of the custom tunnel boring machine.
The Robbins Single Shield TBM will bore a tunnel to replace a 3.8 km (2.4 mi) stretch of the Delaware Aqueduct. The Delaware Aqueduct currently leaks about 75 million liters (20 million gallons) of water per day into the Hudson River. Investigations of the Delaware Aqueduct dating back more than a decade revealed cracks in the tunnel lining. While several inspections with an automated underwater vehicle showed that these cracks were stable, it was determined they could not be fixed from within the existing tunnel. New York City then decided that a new tunnel would be built under the river to bypass the leakage.
To build a bypass tunnel around the aqueduct’s leaking section, Robbins manufactured the 6.8 m (21.6 ft) diameter Single Shield TBM to safely seal against pressures up to 30 bar, and to operate in variable hard rock conditions. The Delaware Aqueduct was completed in 1944. During its original construction, work crews documented groundwater inflows of 7.5 to 15 million liters (2 to 4 million gallons) per day. Because this particular section of the tunnel lies 183 m (600 ft) below the Hudson River, the inflows are under immense head pressure and thus require the unique tunneling technology.
Due to the challenges presented by the Aqueduct Repair, such as difficult geology and considerable water inflows, the TBM had to be designed accordingly. Difficult Ground Solutions (DGS) features, including powerful drilling, grouting, and water inflow control systems have been incorporated into the machine’s design to overcome the expected challenges. “One unique feature of this TBM is the closeable bulkhead, which allows the excavation chamber to be sealed off,” said KSC Tunnel Manager Niels Kofoed. “We expect this to be a key feature in the event that groundwater flows (shunt flows) from the excavated portion of the tunnel cause washout of the annulus grout. Once the bulkhead is closed the groundwater flows are stopped and secondary grouting of the precast liner can be performed, effectively cutting off the flow path of the shunt flows.”
Robbins Project Manager Martino Scialpi further noted that, “the TBM was designed with a 9,500 liter/min (2,500 gallon/min) dewatering capacity. The machine is equipped with two drills in the shields for drilling through the head in 16 different positions and a third drill on the erector to drill through the shields in an additional 14 positions. Drilling and pre-excavation grouting will be a routine job to control and minimize water inflows.” In addition, water-powered, high pressure down-the-hole-hammers will allow for drilling 60 to 100 m (200 to 330 ft) ahead of the machine at pressures up to 20 bar if necessary.
In order to provide access to launch and retrieve tunneling equipment, two deep shafts were constructed in the towns of Newburgh and Wappinger, New York, where the bypass will begin and end. The
project site itself poses challenges to the assembly and launch of the TBM because of the limited space available.
Robbins worked closely with KSC to ensure that TBM components were designed and sized so all could be lifted with the contractor’s hoist system and fit down the narrow, 270 m (885 ft) deep shaft. Once assembled, the machine is expected to begin boring in autumn 2017.
Robbins Double Shield digs the Andes
Chile’s Los Condores HEPP is a high cover, hard rock challenge, with 500 m (1,640 ft) of rock above the tunnel and a high-altitude jobsite 2,500 m (8,200 ft) above sea level. As of January 2017, a 4.56 m (15.0 ft) Robbins Double Shield TBM had completed boring its 900 m (2,950 ft) long access tunnel and was well on the way to boring the first section of headrace tunnel. The machine embarked on its journey on May 27, 2016, and has since excavated over 1,300 m (4,270 ft) of tunnel in total.
The journey to machine launch was an arduous one, requiring shipment of TBM components and vehicle transport on unpaved, mountainous roads. Contractor Ferrovial Agroman is responsible for the intake tunnel at the Los Condores Hydroelectric Project, and was well aware of the challenges associated with machine launch: “The location of the work is a big constraint due to its rugged terrain and geographical location in the Andes. With all this, we are anxious to perform work in an efficient manner,” said Pello Idigoras, Tunnel Production Manager for Ferrovial Agroman.
The jobsite, located 360 km (224 mi) south of Santiago, Chile, is part of a new 150 MW power plant and intake tunnel. The Robbins Double Shield TBM is boring two sections of the intake tunnel, the first measuring 6 km (3.7 mi) and the second measuring 4.4 km (2.7 mi). A section between the two tunnels will be excavated by drill and blast to connect them, making the intake tunnel about 12 km (7.5 mi) in length. “This project brings an increase in energy production in the country, thus contributing to the overall improvement in the welfare of its citizens,” said Idigoras of the effect the completed hydropower project will have on surrounding areas.
The tunnel, located in the mountainous Maule Region of Chile, is being bored in two types of rock: sedimentary and volcanic. The rock has been tested at strengths up to 100 MPa (14,500 psi) UCS, with at least two fault zones””the first of which has already been traversed in rhyolite, andesite, tuff, and breccia. For Idigoras, the conditions are well-suited to Double Shield tunneling: “We have good quality medium to hard rock for Double Shield excavation overall,” he said. Despite that, some areas of challenging ground persist. To cope with the conditions, including steadily increasing water inflows at rates of up to 3,500 l/min (925 gal/min), the contractor is utilizing cementitious grouting and chemical grouting with polyurethane and foam. Such ground conditioning techniques were anticipated and the Robbins Double shield was designed to effectively apply these techniques.
As the TBM excavates, it is lining the tunnel with 250 mm (10 in) thick, 1.2 m (3.9 ft) long concrete segments in a 4+1 arrangement. The machine is currently progressing at a rate of up to 25 rings per 20 hours of boring. Crews are operating in two 10-hour shifts with one 4-hour shift dedicated to maintenance. Idigoras sees the TBM performance and completion of the access tunnel as huge project milestones, though much work remains to be done. “After many months working in engineering, manufacturing, installation, and commissioning, we are proud to see this result. It would be impossible to name all the people who participated in this project thus far but they, as a whole, have managed to get the TBM started digging and boring well.”
Robbins TBM dubbed "Driller Mike" digs Atlanta
After an Onsite First Time Assembly (OFTA) lasting just 2.5 months, Atlanta Georgia, USA’s newest TBM, dubbed “Driller Mike”, made its initial startup on October 13, 2016 and ramped up to full production two weeks later. Atlanta’s Mayor Kasim Reed and city officials gathered with local and national media to celebrate the occasion. The 3.8 m (12.5 ft) diameter Robbins Main Beam TBM is now boring the 8.0 km (5.0 mi) Bellwood Tunnel after being walked forward 100 ft into a starter tunnel. The Bellwood Tunnel path will travel from an inactive quarry and run below a water treatment plant and reservoir before ending next to the Chattahoochee River.
The project was green-lighted by the City of Atlanta’s Department of Watershed Management due to the city’s current emergency water supply shortage. The PC/Russell JV, the project’s construction manager at risk, sub-contracted with the Atkinson/Technique JV to operate the TBM and will oversee construction of various intake and pumping shafts as well as final lining operations. The project is of utmost importance for the City of Atlanta, explained Bob Huie, Sr. Project Manager for the PC/Russell JV. “Right now, the downtown area’s emergency water supply is approximately three days. With the tunnel the supply will increase to between 30 and 90 days. To be a part of the city’s emergency water supply solution is huge. This tunnel will protect the city for a very long time.”
With the tunnel on the fast track, swift TBM assembly was key. The OFTA process involved coordination by multiple crews at the large quarry site. “The OFTA went very well. The overall assembly process was well organized and supervised by the Atkinson/Technique JV and Robbins. We had a good team of folks to put it all together,” said Huie. He continued: “This is a unique job where there’s a lot of people with a variety of backgrounds, but everyone came together to make the OFTA happen.”
The Robbins TBM is now excavating in granite, with at least 300 m (1,000 ft) of zones in three separate areas that will require continuous probing. In a section directly below an existing reservoir, monitoring will be particularly crucial to ensure no water inflows occur. The Robbins machine will also be required to negotiate several curves: “We have one curve in the first 300 m (1,000 ft) and the main 370 m (1,200 ft) radius curve is 1,800 m (6,000 ft) in. We plan to do short TBM strokes in this section™bout 20 cm (8 inches) to 30 cm (1 ft) shorter than normal to get through the curves,” said Larry Weslowski, Tunneling Superintendent for the PC/Russell JV.
Excavation is scheduled to be completed in the first quarter of 2018. After final lining, the tunnel will be filled with water and the quarry site will become Atlanta’s largest reservoir and park, totaling hundreds of acres. While the park site is a bonus for residents, the water storage capacity it will provide is critical. Nearly 1.2 million customers, including 200,000 passengers who pass through the world’s busiest airport every day, count on the water supply each time they turn on the tap. “If the city were to lose water supply for a day, the estimated economic impact would be at least USD $100 million per day. If you consider that this is a USD $300 million project, that seems a pretty good investment in comparison to what could happen,” said Huie.
Bangalore Fanfare Marks Final Breakthrough for Robbins EPB
On September 23, 2016, Bangalore’s last TBM for the city’s metro rail project broke through, marking the end of TBM tunneling on the Namma Metro phase 1. The Robbins-operated machine, known as “Krishna”, bored a 750 m (2,460 ft) drive through challenging conditions between Chickpet and Majestic stations. Cleanup and final commissioning of the tunnel will be completed in 2017, and is the last obstacle before owner Bangalore Metro Rail Corporation Ltd. (BMRCL) can open the Malleswaram-Majestic link. The TBM’s sister machine, “Kaveri”, completed a parallel tunnel in June 2016.
The success follows a gauntlet of challenges on the two tunnel sites. Due to severe delays on the original tunnel drives, Robbins was approached and asked to take over the operations of the remaining two competitor-manufactured TBMs in February 2015. After obtaining agreement from the project owner and the contractor, Robbins took over the responsibility for all aspects of the underground operations. “We provided a team of over 60 staff including TBM operators, TBM technicians, ring builders, a grouting team, and more. We were also responsible for running surface installations and equipment such as the grout batching plant, gantry cranes and power supply. Contractor Coastal Projects Ltd. (CPL) provided a team of people including surveyors, QC engineers, and loco operators who reported directly to our site management team,” explained Jim Clark, Projects Manager for Robbins India.
The Robbins crew carried out tunneling operations while the Chickpet station was being constructed around them to mitigate delays incurred before they took over project operations. The project’s most difficult challenges included a low overburden and unconsolidated ground along the alignment, and the discovery of several uncharted wells directly on the alignment. Difficult ground frequently prevented proper pressurization during cutting tool replacement, requiring a grout solution to be pumped in to fill voids and left to cure. Initially the curing process took up to 36 hours, but with improved application methods this was reduced to a 12-hour curing time.
Another challenge involved the sensitive building structures along the tunnel path. Issues with surface vibration, explained Clark, required that cutterhead speed be limited to 1.8 RPM during the day shift and 1.2 RPM during the night shift. Despite the obstacles, the TBMs advanced at rates of up to 50mm (2 in)/min in highly weathered rock.
“This is an industry first, wherein a TBM manufacturer has utilized their in-house expertise and knowledge to take on this level of responsibility for a project,” said Clark, addressing the magnitude of the successful breakthroughs. “The fact that it was “˜a first’ and we were successful in bringing this high-profile project back on track is a great achievement for The Robbins Company.”
Now that tunneling is complete, the North and South runs of the Namma metro will be connected–a line that, once in service, will carry an estimated 40,000 passengers daily. It is anticipated that Phase One of the metro will be opened in its entirety in 2017.