Category: White Papers
Rescue and Refurbishment of a TBM inundated with Flood Waters at the New York City Harbor Siphon Project
In October 2012, New York City’s Harbor Siphons Project and its 3.6 m CAT EPB ground to a halt when hit by Superstorm Sandy. Despite contractor Tully/OHL JV’s best efforts to mitigate anticipated flood risks, the launch shaft was inundated with seawater, flooding the tunnel and TBM just 460 m into the 2.9 km long drive. A team of Robbins and OHL personnel were able to document, reverse engineer, and refurbish severely corroded components of the TBM while in the tunnel, resulting in a successful re-launch in April 2014. This paper will document the incredible efforts of the team to rescue and refurbish the TBM, and its performance since the restart.
Dual Mode, “Crossover” Type Tunnel Boring Machines: A Unique Solution for Mixed Ground in the Middle East
While both Hard Rock Tunnel Boring Machines (TBMs) and Earth Pressure Balance (EPB) machines have been in existence for 50 years or more, the prevalence of mixed ground tunnels can make their use problematic. In many tunnels with both sections of hard rock and softer EPB type ground, the only historical solution was to use multiple machines or sacrifice efficiency by using just one machine type. Today, Dual Mode, “Crossover” type machines are edging TBMs into new territory by employing design elements from both EPB and Hard Rock Single Shield Machines. Where multiple machine types might have once been used, a Crossover Rock/EPB machine can excavate an entire tunnel in vastly different conditions. The machine type is particularly useful in fractured and faulted weak rock where clay inseams and sections of soft ground may be present. New designs are making this versatile take on tunnelling more efficient, even at larger diameters of 12 meters or more. This paper will explore modern trends in mixed ground TBM tunnelling, including Crossover EPB/Rock Designs that could be applied to the weak/soft rock so often encountered in Middle East tunnelling. It will also look at other Crossover machines being introduced into the industry, including Crossover EPB/Slurry TBMs for tunnelling in high pressure conditions.
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.
While continuous conveyors have become the muck removal system of choice in long, hard rock TBM tunnels, they have gained acceptance in soft ground tunnels only recently. Soft ground, EPB TBM-driven tunnels provide a challenging environment for continuous conveyors due to the variety of materials present. The design of both horizontal and vertical soft ground conveyors will vary depending on the types of excavated material, amount of water present, and other factors. This paper will address the challenges of effective conveyance in different ground materials by analyzing conveyor performance in several recent EPB TBM projects.
- TBMs For Norwegian Small Hydropower Projects
- Completing Mexico City’s Mixed Ground Mega Tunnel: Emisor Oriente
- Project Clear: Efficient Hard Rock Tunneling below St. Louis, Missouri
- Rebuilding TBMs: Are Used TBMs as Good as New?
- Breaking Through Tough Ground in the Himalayas: Nepal's First TBM