Whether in the east, west, north or south, global tunneling and underground development – worth $100 billion annually – remains a buoyant and dynamic sector. And more growth could be expected with increasing needs for mining applications and rising urban populations leading municipalities to seek underground solutions.
2016 seems to be a particularly record-breaking year: the recent opening of the Gotthard Tunnel (Dec. 11) through the Alps in Switzerland exemplifies the outstanding size of projects launched and completed to date. Even though the activity has historically been very strong in Europe and North America, new trends have emerged in the past few years: nowadays, almost 60% of tunnelling projects are located in Asia with 29 cities in China currently extending or building metro systems. Also, South America is experiencing growth in the tunneling industry.
This healthy dynamic in the tunneling industry is reinforced by the innovations that allow better efficiency and understanding of the technical parameters of excavation. These innovations are exemplified by a few below.
Automatic Inspection Vehicle (AIV)
The automatic inspection vehicle (AIV) (essentially a robot) is a virtual assistant designed to connect scientific data to maintenance crews and alert them in case of emergency. This technical innovation is aimed to improve safety and operational surveillance and help fire-fighters in the event of a fire.
The cylindrical robot runs along a continuous steel beam mounted on the underside of the tunnel crown. Gliding along the beam, the unit deploys CCTV and video analytics (VA) to conduct automated inspections. The AIV utilizes VA algorithms to detect abnormal conditions in a tunnel and can detect water leakages, flooding and faulty lights.
To detect any unusual events in the tunnel, the automated video analytics scans the large files of captured video footage using various image processing algorithms and pattern recognition. VA condition monitoring allows early detection prior to any potential disruptive events: the system maps the video feed of the tunnel’s internal structure and equipment, storing it in a database for rapid post-event analysis and future reference. Any abnormality can be detected automatically, when images from different time frames are reviewed and compared. For example, it can pick up new events such as water leaks, flooding or faulty lights because they differ from the stored data.
Locating personnel in the tunnel is captured by a separate system called Radio Frequency Identification that works in tandem with the AIV. The personnel location is recorded and data analysed for investigation and potential follow-up.
In a fire scenario, the fire detection system provides the exact location to allow the AIV to maneuver itself to provide visual coverage, alerting maintenance crews on the location and cause of the fire. Furthermore, the AIV can be manually controlled to allow informed decision making without endangering personnel escaping the tunnel.
Hybrid EPB TBM
Contractor Consórcio Linha 4 Sul used pioneering Hybrid EPB innovation to build the Line 4 of the Rio metro last summer, involving 5.2 km of excavation. The initial 400 m began in hard abrasive gneiss while the middle section (around 3 km) was excavated in sands.
Until recently, tunneling in pure sands was a technical challenge due to the high permeability and granular characteristics. Advancing EPB technology allows new hybrid EPB machines to take up this challenge. On Line 4 of the Rio metro, an 11.51-m diameter hybrid EPB machine mined in pure sand with no or very low (<5%) fine particle content.
Under the water table, the hybrid machine is reported to have achieved accurate face-support pressure and settlement control in pure sands, thereby extending the application, flexibility and versatility of EPB technology. Thanks to these new machines, no separation plant is needed thereby bringing savings in cost, logistics and manpower.
Hybrid EPB shields include ground conditioning with foams, polymers and slurry directly at the cutterhead through the cutterhead nozzles to adequately condition the ground when lack of fines produces problems in face support pressure-control or excessive muck temperature.
The Hybrid EPB technology works along the lines of the earth pressure support concept, with the excavation chamber always full of solid muck. This is designed to give an extra level of safety.
In addition, although compared to conventional EPB shields the new hybrid EPB technology consumes higher levels of foam and slurry, it nevertheless uses considerably less bentonite than slurry shield technology. Furthermore, Hybrid EPB technology allows hyperbaric interventions to take place with the same degree of safety as slurry shield technology. This also provides contractors with greater flexibility for programing cutterhead inspections since it is not necessary to fix in advance the locations for hyperbaric interventions. Such interventions can be carried out safely at any location as soon as there are signs of tool wear.
Aiming to improve quality and productivity in drill-and-blast, Sandvik has developed geoSURE to meet the growing need for measurement while drilling (MWD) data in tunneling. GeoSURE is designed as a convenient way to provide high-accuracy geological data. It achieves this by analyzing and collecting data automatically during drilling, then transferring the results to the office in conjunction with typical process and quality data. The results can be viewed using geoSURE’s visualization features that range from single-hole measurement graphs to 3D data views along the full tunnel line.
Information can be provided on rock strength and fracturing, as well as detecting water in fractures. Analyses are said to be at very high resolution; the effects of the operator, rig and other influencing factors can be compensated for (so the results are purely about rock-mass properties) and the results are instantly available.
MWD data capture includes assessment of rock support need and selection of suitable methods, blasting control and optimization, prediction of rock mass conditions ahead of the tunnel face, planning and optimization of resources, and work plans for upcoming rounds. The data can also be used as assisting information in life-time maintenance and renovation of the tunnel, and as a source of data in troubleshooting. Results with geoSURE are immediately available without delays in analysis.
BBMV has helped develop the Uphill Excavator, which – suspended from a rail on the tunnel crown – bores inclined tunnels from bottom to top on up to 30 degree inclines. One was used at two locations on Crossrail (C510) to bore pilot tunnels in London Clay for 9-m diameter escalator barrels.
The machine comprises an excavating and shotcrete-spraying arm complete with an operator’s cab. These are suspended from the tunnel crown via a rail system installed as the excavator progresses with the tunnel advance. Running alongside the excavator is a bespoke walkway that gives the engineer a safe location from which to carry out his work, while still being in visual and audible communication with the operator. The walkway also provides emergency egress for the operator at any point during the tunneling operation.
This innovation not only improves safety by keeping operators away from dangerous areas, but also eliminates large quantities of temporary works that would have been required in the shafts to allow downhill construction.
The Uphill Excavator allows users to carry out inclined excavations from the confines of the main site without disturbing the connecting shaft, thereby reducing the impact of construction on the local environment and community.
GTA has manufactured suspended systems for the mining and rail industries in Germany for 40 years. Combining ‘Lasershell’ tunnel lining with GTA technology, BBMV’s innovation is an excavator suspended away from the tunnel invert and which can propel itself up a 30-degree incline.
Sprayed Concrete Lining
Finally, new research in Norway on the physical properties of fiber-reinforced sprayed concrete and sprayed membrane materials in a bonded context have uncovered some interesting findings. They suggest that degrading mechanisms such as long-term leaching of sprayed concrete, exposure to aggressive ions from groundwater, the build-up of hydrostatic pressure in the lining structure and freeze/thaw-induced damage are very unlikely to occur. The project findings bring a new perspective on the properties and possible use of wet-mix sprayed concrete and sprayed membranes.
Overview of Projects Underway Worldwide
• The Deep Tunnel Sewerage System, Singapore
• The Jurong Rock Caverns, Singapore
• Thomson East Coast Line, Singapore
• The New Guanjiao Tunnel, China
• Xi’an, Shenzen, Shanghai, Chengdu metro extensions, China
• Wan Chai Bypass, Hong Kong, China
• Klang Valley, Kuala Lumpur, Malaysia
• Mumbai, Kolkata, Dehli metro, India
• Zojila tunnel, India
• Teheran-Mazandaran highway, Iran
• Gaoligongshan Railway Tunnel, China
• Muzailing Railway Tunnel, China
• Hong Kong-Zhuhai-Macau Highway Immersed Tunnel, China
• Que’ershan Highway Tunnel, China
• Opening Metro Line 4 in Rio, Brazil
• Sarmiento railway, Argentina
• Duplications of Joa and Pepino Tunnels, Brazil
• Agua Negra road tunnel, Argentina-Chile
• Toya tunnel, Colombia
• California Fix Water Program, USA
• Seattle Alaskan Way, USA
• New York 2nd Avenue, USA
• Metro Vancouver, Canada
• Coxwell Bypass, Toronto, Canada
• Grand Paris Project, France
• Ryfast scheme, Norway
• Venda Nova Project, Portugal
• Brenner Tunnel, Austria-Italy
• Thames Tideway Tunnel, UK
• Swina tunnel, Poland
This report was contributed by the International Tunnelling Association (ITA).