Category: White Papers
TBM operator cabs and controls are often a long way down the list of priorities when it comes to the overall design of a Tunnel Boring Machine. However, their proper design and inclusion of the latest technology can mean the difference between a successful project and an unsuccessful one.
On soft ground machines the industry often puts operators in control of machines with little or no practical experience of that particular machine or the control systems. This practice can, in some cases, lead to major incidents such as ground heave or sinkholes in densely populated urban zones causing major disruption, downtime and untold damages and cost.
This paper will discuss the advances and developments in TBM operator controls and the use of “command chair” technology as both a training tool in the form of a boring machine simulator and as a way of controlling modern-day TBMs.
Rondout West Branch Bypass Tunnel—TBM Boring in Hard Rock Against High Water Pressure and High Water Inflows Beneath the Hudson River in New York
This paper focuses on a single shield hard rock tunnel boring machine that is set to bore in hard rock, high water inflows and high water pressure in New York State. To overcome the difficult conditions the TBM is designed to handle 2500 gpm water inflows and seal against 30 bar of pressure. The TBM will bore a tunnel to replace a damaged portion of the Delaware Aqueduct that supplies half the raw water to New York City. The 2.5 mile bypass tunnel passes beneath the Hudson River with geology consisting of shale and limestone.
Due to the high water pressure and inflows, the TBM was designed with new sealing systems for the main bearing and to close the TBM off if high water inflows are encountered. The TBM is to be equipped with two dewatering systems and multiple drilling and grouting systems for pre excavation grouting and segmental lining backfill. Systematic drilling and grouting procedures specific to the project were developed and incorporated into the TBM and backup design to ensure that the TBM can handle the extremely difficult ground conditions of the project.
In mechanized tunneling, continuous information from the excavation face is essential. The ultimate goals of cutter instrumentation are to monitor real-time individual cutter operation, acquire more realistic cutterhead thrust force values, and gain a better knowledge of the geology in front of the cutterhead. Analysis of this information can provide in-depth knowledge of machine excavation. Information about cutter operation has direct and indirect advantages: It helps better predict and monitor cutter usage rates, and it can reduce the cost of unplanned cutter or ring replacement, which can result in a better planning of inventory, manpower, and cutter rebuild requirements.
Current disc cutter instrumentation technology is designed to be a conveniently mounted instrumentation package that monitors individual cutter rpm, wear, temperature, and vibration. A data logger service receives the cutter information wirelessly using low-power radio technology and displays cutter conditions in real time. With cutter instrumentation, the operator continuously monitors cutter conditions, which results in higher efficiency, lower incidence of down time, and prevents unexpected ring wear-related damage from causing further damage to bearings and hubs. Cutter instrumentation technology has been tested on Robbins’ rock machines and results from previous and recent projects are presented. Design improvements for longer lifetime and increased reliability are discussed.
High Cover TBM Tunneling in the Andes Mountains—A Comparative Study of Two Challenging Tunnel Projects in Chile
The Andes Mountain range is among the youngest and most complex in the world, geologically speaking. Tunneling projects, particularly for hydroelectric and water transfer schemes, are not new to the range but their past history has met with mixed success. Two new projects utilizing very different tunnel boring machines and excavation strategies are now providing a testing ground for modern underground construction equipment in the Chilean Andes.
This paper will analyze two projects: the Alto Maipo and Los Condores Hydroelectric Projects, located approximately 100 km apart in the Andes Mountains. The two strategies being employed will be analyzed in detail, as one project is using an open-type Main Beam TBM plus extensive ground support, while the other is utilizing a Double Shield TBM and segmental lining. The authors will look at TBM performance and ground conditions encountered in the two tunnels and what effects the TBM selection and ground support strategy may have had on each tunneling operation.
Successful Excavation of Mexico City’s Emisor Poniente II Wastewater Tunnel—Use of a Dual-Mode, Crossover TBM in Challenging Geology
The history of Mexico City is inextricably linked to the issue of its geographic location. In the last 100 years, Mexico City has sunk by nearly 12 m. As a result, the city’s buildings, main streets, sewage systems, etc. have been extensively damaged.
In July 2015, the launch of a dual mode, Crossover type TBM marked the start of Mexico City’s next challenging wastewater project: the Túnel Emisor Poniente (TEP II). The 5.5 km long tunnel travels below a mountain at depths of 170 m as well as a section just 8 m below residential buildings, and the geology is equally varied. Ground consists of andesite and dacite with bands of tuff and fault zones, as well as a section of soft ground at the tunnel terminus.
This paper will detail the unique 8.7 m diameter Crossover TBM designed for the challenging conditions, and the successful excavation of the machine through fault zones, soft ground, and more. Strategies for excavation and advance rates, and downtimes will be analyzed. As the machine can be converted from hard rock mode to EPB mode in the tunnel, the authors will also look at the conversion process and how both modes worked to excavate in widely varying geological conditions.
Design and Implementation of a Large-Diameter, Dual-Mode “Crossover” TBM for the Akron Ohio Canal Interceptor Tunnel
The Ohio Canal Interceptor Tunnel (OCIT) Project involves construction of a conveyance and storage tunnel system to control combined sewer overflows for several regulators in the downtown Akron area. A Robbins dual mode type “Crossover” (XRE) Rock/ EPB TBM, Ø9.26m bore in diameter, will be used to excavate the tunnel and install the precast segmental lining.
The XRE TBM will feature characteristics of both Single Shield Hard Rock machines and EPBs for efficient excavation in mixed soils with rock, such as a flexible cutterhead design for proficient boring in both rock and soil conditions, adjustable main drive speed with an over-speed mode for operation in hard rock, and special screw conveyor wear protection measures. This paper describes these design features, their manufacturing process, and implementation in the field.
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.
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.
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.
- Rebuilding TBMs: Are Used TBMs as Good as New?
- Breaking Through Tough Ground in the Himalayas: Nepal's First TBM
- Tunneling in Mixed Face Conditions: An Enduring Challenge for EPB TBM Excavation
- 7.93 m Open TBM Shotcrete System Improvement and Innovation - Jilin Project, China
- Overcoming Extreme Tunneling Conditions in Vietnam's Longest Tunnel