Carving a Path Through Extreme Conditions: An Integrated Ground Investigation System Optimized For Turkey's Difficult Geology
Turkey’s geologic framework, seated on an active tectonic belt, is made up of older rocks mixed with younger igneous rock. More than 80% of the country’s surface is rough and mountainous, and the ground conditions can be highly variable and unpredictable. Today’s adaptable TBMs are capable of tackling these tough conditions using cutting-edge technology coupled with modern ground investigation methods.
This presentation will explore several recent and ongoing projects in the tunneling industry that highlight the latest in TBM technology for difficult ground excavation. Whether smart features include a Measurement While Drilling (MWD) system, cutterhead inspection cameras, or sensors to monitor converging ground, today’s TBMs equip contractors with knowledge. Specialized sealing systems can arm contractors with methods to successfully and safely treat water head pressure up to 30 bar.
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.
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.
Montreal, Quebec, Canada’s Rosemont Reservoir tunnel travels for 4.0 km below city streets, faulted rock, a disused quarry, and active subway. The story of the 3.0 m diameter Double Shield TBM’s successful breakthrough involves a careful analysis of geology, TBM operating parameters, and ground consolidation measures. Over the years, geologists conducted two diamond-drilling programs totaling 65 borehole tests to depths ranging from 21 to 65 m below residential and commercial neighborhoods along the tunnel alignment. The core sampling program indicated the presence of medium to thinly bedded limestone, with some shale and intrusive rocks, mainly dykes and sills. While the limestone averaged 50 to 300 MPa UCS, rock in the intrusives ranged from 100 to 430 MPa. More than 80 dykes and sills as small as a few centimeters wide and as large as 8 to 10 m wide were mapped along the 4.0 km tunnel. Contractor Foraction, Inc. took measures including cement injection of vertical boreholes in two suspected fault zones from the surface to a depth of 50 m. Even with these measures, fractured rock and water inflows, which had to be temporarily deviated, slowed progress and required alteration of the boring parameters in some sections. The crew were ultimately successful and made their final breakthrough with the TBM in November 2015. This paper will analyze TBM boring methods and performance based on the changing geological conditions below Montreal. Special attention will be paid to sections in fracture zones and below sensitive structures including the inactive quarry site and active Montreal subway. The authors will analyze how preliminary studies, combined with operational techniques and on-going geological monitoring, resulted in an ultimately very efficient tunnel boring project in a dense urban area.
On Tuesday, September 6, 2016, one of the longest-running Robbins TBMs embarked on its most extensive project yet. The 6.2 m (20.2 ft) Main Beam machine, owned by the Shea-Kiewit (S-K) JV, is boring the 8.5 km (5.3 mi) long White River Tunnel as the first in the next phase of the DigIndy wastewater tunnels below Indianapolis, Indiana, USA. In addition to that work, the machine will bore the Lower Pogues Run, Fall Creek, and Pleasant Run Tunnels™ scope of work totaling about 28 km (17 mi) through limestone and dolomite rock.
The rebuilt Robbins hard rock TBM was first used in Indianapolis on the 12.5 km (7.8 mi) long main tunnel, called the Deep Rock Tunnel Connector (DRTC). On that tunnel, the speedy machine 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). “It’s nice to start the job with a machine that has already been proven and successful,” said Stuart Lipofsky, Project Manager for S-K JV.
However the DRTC was far from the TBM’s first job. The machine, originally built in 1980, has been used on New York City’s Second Avenue Subway, as well as projects in Massachusetts and Canada. Once the machine has completed the DigIndy network of tunnels, it will have bored more than 51 km (32 mi) of tunnel™n achievement making it one of the hardest working Robbins TBMs ever put into service. “The age of the machine wasn’t a concern for us, it was a positive. We knew it could perform in harder, abrasive rock,” said Lipofsky.
The machine was launched from the 67 m (220 ft) deep White River shaft following a refurbishment that included new motors, gearboxes, electronics, and other elements. As of the last week of September, the TBM has bored over 300 m (1,000 ft) of the White River Tunnel. About one mile into the White River Tunnel, the drive will bifurcate eastwards to bore the 2.7 km Lower Pogues Run Tunnel in front of Lucas Oil Stadium in downtown Indianapolis. The machine will then be backed up to the bifurcation point before continuing north for completion of the White River Tunnel.
As the machine bores, Robbins continuous conveyors remove muck in an extensive system that was highly successful at the DRTC. Much of the conveyor structure remains the same for the new tunnels, with new horizontal and conveyor belting provided. The conveyors will wind through curves as sharp as 300 m (1,000 ft) in radius, as the tunnels follow the path of the White River overhead.
The S-K JV has until 2021 to complete the White River and Lower Pogues Run tunnels for local owner Citizens Energy Group, and until 2024 to complete all the tunnels. The use of one TBM was seen as a positive: “The use of one machine was more efficient for our crews. The schedule allowed us to run with one TBM and we feel we can do it with one machine. It also was a less costly option than running two machines in terms of the owner funding the project,” said Dan Martz, vice president for J.F. Shea. Once complete, the EPA-mandated deep tunnel project will reduce the amount of raw sewage overflows and clean up tributaries along the White River.
The Robbins Rockhead is a mid-sized tunneling machine available in both Single Shield and Double Shield models. Ranging between 54 inch (1.35 m) and 78 inch (2.00 m), the Rockhead is the ultimate solution for line-and-grade critical bores that are over 1,000 ft (300 m) in length. Watch this 3D animation to learn more about these powerful machines.
The Robbins Company announced the appointment of Joe Lechner to the role of Small Boring Unit (SBU) Sales Manager. With over 18 years of industry experience, the role is a natural career progression for Lechner. It brings him back to his early roots of working with SBUs, while more recently he worked with TBMs. Lechner can continue his success with the company in this new capacity with the trenchless division.
In his new position, Lechner will handle SBU sales and rentals for Robbins, assist customers in equipment specifications for projects, and provide full-spectrum customer support. In addition, Lechner will be responsible for many other tasks such as generating quotes for cutters and spare parts, shop scheduling, forecasting, internal operations for Robbins, and field service support, as needed.
“I want customers to know they can come to me with any issues. I have a good understanding of the industry and our business,” said Lechner. “I want to provide an all-around good experience. Robbins wants your project to be successful, with our equipment and support.”
Lechner began working with SBUs in 1998, starting in field service. When he wasn’t out in the field, he was building SBUs and cutters. He started up and commissioned SBU-As in the field, and transitioned over to working with TBMs worldwide in the mid 2000’s. With his diverse worldwide field experience, Lechner’s knowledge will continue to benefit Robbins and its customers.
Lechner said his goals as Sales Manager for the SBU product line for the next two years include increasing stocking levels and providing fast deliveries to customers. He noted the division is streamlining inspection quoting and repair processes to ultimately provide the most efficient services possible. With a few hundred machines in service, some of which are working around the clock, he anticipates product sales, rentals and repairs all will remain consistent moving forward.
“We’re lucky to have Joe working with Robbins,” said Tom Fuerst, Utility Tunneling Sales Manager. “With his background and extensive knowledge, he’ll easily implement the best solutions for our customers.”
In February 2015, Robbins, with its operating company Robbins India, was asked by Bangalore Metro Rail Corporation Limited to take over the operation and maintenance of two competitor-owned EPBMs. The machines were stalled due to low performance and financial issues from the Operating Contractor and lack of support by the original machine supplier. As the North-South Bangalore Phase 1 Metro tunnels were on the critical path, the BMRC looked to Robbins to step in and take over the troubled project. A Robbins/Robbins India team of 70 field service personnel refurbished and modified the existing equipment, both while in the tunnel and before relaunching the machines in Chickpet station. In addition, the on-site Robbins/Robbins India Team supervised all aspects of TBM excavation, segmental lining, mucking and grout plant operations since the relaunch of the machines for both drives.
“I am particularly proud of being involved in this project, and to support BMRC with the completion of this tunnel drive and bringing the project back on schedule. This is also the first time The Robbins Company has been responsible for the complete scope of operations on a project,” noted Jim Clark, Projects Manager with Robbins India. “One of the biggest challenges we faced was carrying out cutterhead interventions under compressed air in mixed ground conditions that consisted of varying grades of granite in the lower half of the face, and loose, unconsolidated material in the upper section of the face.”
Clark said that on numerous occasions, compressed air would percolate through to the surface, forcing crews to abort cutterhead interventions. They eventually found a solution by pumping a weak mix grout though the mixing chamber, and into the geology surrounding the tunnel face. The weak mix grout stabilized the ground sufficiently so the cutterhead interventions could be completed.
The Robbins crew carried out tunneling operations while the 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 consolidated ground along the alignment, and the discovery of several uncharted wells directly on the alignment. In addition, the majority of the tunnel was bored directly beneath buildings constructed upon what is today considered substandard foundations.
This portion of the Phase One Metro tunnels runs from Chickpet to Majestic at Namma Metro. Once Krishna breaks through, the North and South runs of Bengaluru will be connected, allowing service to an average of 40,000 passengers daily. It is being completed under a tripartite agreement between Robbins India, Coastal Projects Limited, the lead contractor, and project owner, Bangalore Metro Rail Corporation Limited. It is anticipated Phase One will be open in its entirety by November, 2016.
A Novel Continuous Conveyor System and its Role in Record-Setting Rates at the Indianapolis Deep Rock Tunnel Connector
The Indianapolis Deep Rock Tunnel Connector (DRTC)—first in a vast network of storm water storage tunnels below Indiana, USA—was a wildly successful endeavor. Crews for the Shea/Kiewit JV drove a 6.2 m Robbins Main Beam TBM to world record rates. The machine achieved 124.9 m/day, 515.1 m/week, and 1,754 m/month in limestone and dolomite rock. The advance rates can be attributed to many factors including ground conditions and knowledgeable crew, but continuous conveyors are also of key importance.
The novel conveyor system, manufactured by The Robbins Company, enabled continuous tunneling in a difficult layout that included two 90-degree curves and two S-curves. Spanning 11,777 m in its longest iteration, the system included nine booster drives plus a main drive. A vertical belt moved muck up the 76 m deep shaft to a radial stacker for temporary storage. The system, one of the most complex in North America and the first to operate in 90-degree curves, made swift tunneling possible.
This paper will examine the world-class tunneling done at the Indianapolis DRTC and the role of continuous conveyance in reaching high advance rates. The logistics of the system will also be examined as it could apply to future tunneling projects with similarly complex layouts.
Mixed ground tunnels come in all kinds. In rock tunnels with possible faults and high pressure water, the challenges are many. With the advent of Crossover TBMs, contractors can minimize risk in such conditions while maximizing efficiency. The newest generation of Crossover is exemplified by two projects in Albania and Turkey.
A 5.56 m Crossover TBM destined for Turkey’s Gerede Water Transmission will be assembled using Onsite First Time Assembly (OFTA) from within an existing tunnel. The unique machine will bore through 30 fault zones requiring the TBM to be sealable to up to 20 bar so pre-consolidation grouting can be done. EPB mode will only be used in poor ground—in this mode, the TBM will bore sequentially using the screw conveyor fore and aft gates.
Skewing further towards hard rock, a unique 6.2 m diameter Double Shield TBM with Crossover features was designed for Albania’s Moglicë Headrace Tunnel. The machine features closure doors and a sealing system to contain inrushes of water until they can be grouted off.
This paper will discuss the unique aspects of the Crossover designs and their utilization at the two projects.
- Hybrid TBM Excavation in Challenging Mixed Ground Conditions at the Mumbai Metro
- TBM Excavation in Himalayan Geology: Over 1,200 Meters per Month at the Bheri Babai Diversion Multipurpose Project
- Tunneling through 48 Fault Zones and High Water Pressures on Turkey’s Gerede Water Transmission Tunnel
- Overcoming Multiple Caverns: Successful TBM Tunneling in Karst Geology at Galerie des Janots
- TBMs For Norwegian Small Hydropower Projects