Author: The Robbins Company
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.
Find out about Norway’s Røssåga Hydroelectric Project, the first TBM to be used in the country in more than 20 years. Watch in-depth site interviews about machine performance in incredibly hard, abrasive rock, remote site conditions, and the future of TBM use in Norway.
Diminishing surficial mineral deposits, increasing environmental regulation and advanced geological exploration techniques are ushering in a new era of mining. Unconventional technology must be adopted to ensure that safe, efficient and responsible access to minerals is possible as prospecting continues to push the mining industry deeper. This paper discusses why competitive mining operations will become increasingly dependent on Tunnel Boring machines (TBMs) for mine development and expansion, and explores the implications of TBMs in a drill and blast dominated industry.
Lessons learned from construction of the 62km Emisor Oriente Tunnel in Mexico's challenging and varied ground
In April 2009, tunnel boring started on the Tunnel Emisor Oriente (TEO) sewer project after decades of deliberation. The infrastructure will replace an open, untreated canal that conveys wastewater from Mexico City. The new tunnel will end at the capital’s first wastewater treatment plant and reduce the risk of catastrophic flooding in downtown Mexico City. It was this risk that led President Felipe Calderon to label the project a “National Emergency”. The TEO project was designed as a 62 km pipeline of 8.9 m diameter with a primary precast concrete segmental lining and a secondary in-situ concrete lining. 24 shafts up to 150 m deep support six TBM operations totaling about 10 km each. After five years of work, 34% of the bore is complete, and the owner of the project, CONAGUA, is rethinking their strategy based on incredibly difficult ground. This paper will discuss the new strategy from both the contractor and manufacturer perspective, including successful TBM modifications.
Singapore is employing more than 29 earth pressure balance machines (EPBMs) to excavate a single 21 km metro line, Downtown Line 3. Moscow is adding 50 km of new metro line by 2016, 150 km by 2020. China will expand their metro lines tenfold by 2050 to more than 11,700 km. China’s plans for the next two years require 250 EPBMs. With such extensive global metro expansion plans, increasing EPBM performance would have a monumentally positive economic impact, with tunnels being excavated in less time and at lower cost. EPBMs on several projects have recently set performance records. In this paper, the authors examine these and other projects, searching for clues as to why some EPBMs perform at higher rates than others and attempt to determine which causes are in the control of contractors, which in control of the machine designers and how one might replicate high performance on future projects.
Earth Pressure Balance (EPB) tunneling in mixed ground conditions is a challenging prospect, as it often includes excavation in boulder fields, sections of rock, and/or sticky clay, under high water pressure or changing water pressure. Maintaining a rapid advance rate in such conditions is a function of many factors—from adequate cutting tools to cutterhead design, pre-planning and execution of an appropriate ground conditioning regime as well as proper maintenance and operation of the TBM. This paper will analyze recent record-breaking and high-performing projects seeking to identify factors that contribute to fast machine advance. These factors will then be discussed and an effort made to form simple, high level guidelines for optimal TBM excavation in mixed ground conditions.
Modern tunnel boring machines come in a variety of designs that use different excavation methods to address a wide variation of geology seen during tunneling operations. Invariably tunnels of any length run into varying geology, some of which will fall outside the traditional range of any one machine type. On projects where the majority of the drive is rock with a short percentage of a softer formation, selection of a hard rock machine with maximized advance rates, minimized operating cost and wear would be desirable. However, when there are concerns associated with risks of the machine getting stuck, of high water inflow and of subsidence in soft ground, the contractor may be driven towards the choice of a soft ground machine. This paper will review the additional features and ground treatment options that could expand the spectrum of projects benefitting from a hard rock type machine, even when sections of soft ground are present.
Today’s mega metro projects are using multiple TBMs in difficult ground, short tunnels, and in urban settings: Factors that create unique challenges. At Singapore’s metro construction, 21 km of tunnel for the Downtown Line 3 are underway using 29 TBMs boring between 16 station sites in short bores often less than 1.5 km each. By 2017, 39 km of new construction will cut commute times in half in one of the world’s most densely populated locales.
This paper will detail six earth pressure balance machines on the project, analyzing the challenges of boring in a highly urban setting through rock and soft ground under water pressure. Machine performance at the Singapore Downtown Line will be analyzed with a discussion of the challenges involved.
TBM tunneling is an ever-increasing prospect for underground construction, and with each new tunnel bored there are unknown elements. When boring through the earth, even extensive Geotechnical Baseline Reports can miss fault lines, water inflows, squeezing ground, rock bursting, and other types of extreme conditions. This paper will draw on the considerable field service experience within Robbins to analyze successful methods of dealing with the most challenging conditions encountered.
Learn more about the Robbins Motorized Small Boring Unit (SBU-M) in this 3D animation. With continuous steering capabilities and an in-shield drive motor, the SBU-M can make the grade on long gravity sewers and other line and grade sensitive utility tunnels.
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