From the magazine, Microtunnelling, Tunnelling

Tunnelling around the world

The industrial and economic hub of Central China, Wuhan city in Hubei province is currently constructing its subway line two using seven Herrenknecht tunnel boring machines (TBMs) to excavate almost 17 km of tunnel. Five Earth Pressure Balance (EPB) Shields are crossing beneath inner-city areas whilst two Mixshields that specialise in multi-layered, highly water-bearing grounds will cross beneath the Yangtze River.

Eleven million inhabitants of Chengdu in Sichuan province in south western China will soon be able to benefit from an extensive new metro system. After signing a contract in January 2009, Robbins has provided multiple TBMs to China Railway Construction Corp. so that they can build metro lines totalling 126 km in the region best known for its Giant Pandas. A 6.26 m diameter EPB will be used to excavate the tunnel after a mixed ground cutterhead with 17 inch diameter disc cutters and carbide bits has excavated the variable geology, which includes a mix of weathered rocks found nowhere else in China. The Chengdu Metro will be opened in three stages, with the first line set to be in operation by 2010. It is hoped that seven lines will be fully operational by 2035, servicing 13.1 million passengers daily.

The industrial city of Guangzhou, located on the Pearl River Delta in southern China is also currently upgrading its subway as part of a project that has seen the network constantly extended over the past years. At present, more than 105 km of the proposed 140 km have been excavated since 2000 using a mixture of EPB Shield and Mixshield Herrenknecht TBMs with diameters of 6.25 m.

With a population of 20 million, Shanghai is not only the biggest megacity in China, it is also one of the largest metropolises in the world. The Shanghai Yangtze Under River Tunnel was constructed to enable inhabitants of the nearby river island Changxing easy access to the Shanghai of Pudong.

Herrenknecht supplied two TBMs for the construction of the two traffic tunnels in Shanghai, which both tunnelled under the Yangtze River at a depth of 65 m. With a weight of 2,300 tonnes and a length of 125 m each, they were two of the largest tunnel boring machines in the world. The two tunnels, each almost 7.5 km long, were completed after only 20 months and 10 months faster than originally scheduled. The completion of tunnelling work ahead of schedule provides the ideal conditions to open the tunnel on time for the 2010 World Exhibition in Shanghai, which is expected to draw 70 million visitors to the city.


The final tunnel breakthrough has been achieved on the New Delhi Metro project, ready for the influx of visitors for the 2010 Commonwealth Games.

Contractors ALPINE began construction of the project in 2007 that will see 23 km and six stations link the Central Railway Station in New Delhi with the Indira Gandhi International Airport and the district of Dwarka.

With the construction site located directly under three major traffic arteries as well as two existing and operational Metro lines, the work needed to be completed at a depth of 35-45 metres so as to not cause disruptions. With a longitudinal gradient of 2.85 per cent and a water pressure of 4.5 bar, the project presented ALPINE with a challenging task.

“Thanks to our extensive experience we were able to cope with the difficult situation during the headwork and complete the tunnelling in just eleven months,” said ALPINE’s Division Manager for Asia Erich Golger.

Three TBMs were used to construct the 3.86 km twin-tube tunnel project

(2 x 1,540 m + 2 x 670 m) and a cut and cover tunnel of 1.16 km. The project also included construction of the New Delhi and Shivaji Stadium underground stations with a length of 242 m each, as well as the adjoining parking garages.

In February this year, the project set a new milestone for the industry as a Robbins EPB being used on the project achieved a weekly advance rate of 202 m, the highest advance rate amongst any of the 14 TBMs used on the metro project.


Laos will be energising its neighbour Thailand by 2012 thanks to the Theun Hinboun Expansion project which commenced in May this year.

Contracted to CMC di Ravenna, the $US270 million project will expand from 220 to 440 MW of the installed capacity of the existing hydroelectric power plant originally built by Recchi-Cmc JV between 1995 and 1998. The station will draw water from the Nam Theun River in central Laos so that electricity can be sold to Thailand, where current power supplies are struggling to meet demand.

Part of the project will include the construction of a 5.5 km headrace tunnel with a 6.5 m diameter. The tunnel will be constructed using a 7.6 m diameter Robbins Single Shield TBM.

The Robbins TBM has been designed for squeezing ground conditions and will feature an articulating cutterhead with overcutters capable of cutting 100 mm beyond nominal tunnel diameter. Ground along the tunnel alignment consists of alternating levels of sandstone, siltstone and mudstone. Continuous tunnel lining works will support the ground conditions, using 280 mm thick, pre-cast concrete segments.


SN Aboitiz Power (SNAP) awarded McConnell Dowell Philippines Inc. the civil works associated with Ambuklao Hydro project located near Bagio City, Philippines. The project consists of a network of tunnels and shafts and the construction of new intake and outlet structures and is located in the Benguet province in Luzon Island in the Philippines.

The main source of water comes from the Agno River in the Philippine island of Luzon. The Agno River is the main drainage system of the area and has a catchment area of 5,952 square km. The refurbishment of the Ambuklao and Binga Hydropower plants is a high priority, as both plants were commissioned over 40 years ago and have been severely compromised by major siltation and volcanic activity.

New intakes to both stations will be constructed by McConnell Dowell Philippines above the silt level as well as new drop shafts and head race intake tunnels. Other works will include a new surge tunnel, bypass tunnel, silt bypass and tailrace outlet. The Ambuklao hydro power plant will be equipped with new electrical and mechanical equipment, as well as new generators. A complete new cooling system with pipes, pumps and filter as well as new drain system, new spherical valves, runners and shafts will be installed, and new bulkheads will be incorporated to maintain the spillway gates. The Binga hydro power plant will generate 120 MW of power and will achieve an average annual production of 419 GWh. Dam rehabilitation works will be carried out on the spillway and new instrumentation will be installed. Works have commenced onsite and the project is expected to be completed in August 2010.


As part of the Akk̦y II Hydroelectric Project in northeast Turkey, Kolin Construction Co. Inc. used a 4.8 m diameter Robbins Main Bean TBM at two different tunnel diameters.

Diameter change required removal of the outer cutterhead sections, bottom and side supports, roof shield, dust shield, and gripper shoes. The components were then replaced with four metre diameter adaptations before the machine is transported to the smaller tunnel sections.

Tunnels of differing diameters were designed into the Akk̦y II Hydroelectric Project and will be used to transfer water from several sources to reservoirs and dams.

Upon completion, the Akk̦y II Hydroelectric Project will supply 898 million KWh annually to the National Grid at a 54 kV level. The new project will add to the current 315 million KWh supplied by the Akk̦y I Hydroelectric Project.

Meanwhile, in a city renowned for its diverse and unique culture thanks to its traditional role as the gateway between European and Asian empires, works are currently underway in the Turkish capital of Istanbul to continue linking East to West.

The Melen 7 tunnel runs under the Bosporus and is being constructed to provide water from the eastern districts of the city to the west.

A Herrenknecht S-391 TBM was used to excavate the Melen 7 and reached its target shaft in mid-April of this year. The tunnel crosses beneath the Bosporus, the sea strait between the Asian and European parts of the Turkish metropolis and took only 13.5 months to construct.

After beginning construction in March 2008 from the European side of the strait, the machine covered up to 20 m per day. Having been completed earlier this year, the tunnel is expected to begin transporting water from the Asian to the European part of Istanbul from 2010 onwards.

The biggest challenge within the project was excavating at a depth of up to 135 m. As such, the machine had to be sealed to withstand water pressures of up to 13.5 bar.

Home to more than 10 million people, Istanbul will rely on the Melen 7 tunnel to provide large-scale water sustainability, suppling drinking water, as well as agriculture and regional industries.

This project marks the first connection between two continents created by a tunnelling machine.

United Arab Emirates

Italian engineering firm Impreglio will build the first 15 km of a 40 km hydraulic tunnel to be constructed in Abu Dhabi.

Having been awarded the $US243 million contract to construct the first of three lots of the Strategic Tunnel Enhancement Project (STEP) by the Abu Dhabi Sewerage Services Company (ADSSC), Impreglio will begin construction of the gravity tunnel to collect waste water on the Abu Dhabi island and mainland and convey it to the treatment plant in Al Wathba by the end of 2009.

The 40 km long tunnel will have an excavated diameter of 6.3 m and six access shafts to depths of between 40 and 50 m.

STEP will provide all involved parties with logistic and technical challenges, as it will involve simultaneous use of three EPB TBMs to excavate and case the tunnel with precast concrete sections. The project marks the first time such advanced mechanised technology has been used in Abu Dhabi.

The hydraulic tunnel and the access shafts will be lined with a special membrane to keep the concrete sections fully protected against the aggressive environment, for a minimum duration of 100 years.


Works to extend Switzerland’s rail networks are running ahead of schedule, as Herrenknecht’s in Switzerland. TBM Gabi 2 reached its target in the western tube of the Gotthard Base Tunnel in Amsteg in mid September, six months earlier than expected.

With a diameter of 9.58 m, Gabi 2 excavated 7.2 km in only 18 months. The average daily tunnelling performance through hard rock and mountain overburdens of up to 1,000 m was approximately 18 m. Gabi 2’s best daily performance was 52 m of excavated and secured tunnel, which is a world record for a TBM of such size.

Almost 91 per cent of the Gotthard tunnel system has been completed of the total 151.8 km to be excavated. Excavation work in the world’s longest railway tunnel has now been completed on the northern side of the Gotthard Range. The main breakthrough between Sedrun and Faido is due to take place by the beginning of 2011 and commercial rail operations are planned to commence at the end of 2017.


As part of a major rail expansion in Slovakia, the Slovakian Rail Administration has contracted Skanska to construct a tunnel.

The $US79 million project includes the construction of a 1.8 km tunnel that will house double tracks for high-speed trains. The tunnel will comprise part of the expansion of the 17 km section of line between Nove Mesto and Zlatovce in Western Slovakia.

The tunnel will comprise part of the expansion of the 17.7 km section of line between Nove Mesto and Zlatovce in Western Slovakia. Skanska is part of a syndicate with Czech and Slovakian construction companies which will implement the rail expansion, totalling $US396 million.

Work on the tunnel will commence immediately and is expected to be completed in April 2013.


Robbins opened up a new office in Mexico City in March 2009 to provide services on two local mega projects using four Robbins EPBs.

The city’s new metro line, which will utilise a 10.2 metre diameter DPB on a 6.2 km long tunnel began construction in late 2009. Robbins will also provide three EPBs in 2010 to work on the 62 km long wastewater line.

The office has been established to provide project management, TBM field service, conveyer systems service and sales functions in Mexico and other Spanish-speaking countries in Latin America.

“There is a lot of work coming up in Mexico, and it is an important new market for us. The office will serve as a centre of operations for both current and future projects,” said General Manager of Robbins Mexico Roberto Gonzalez.

United States

In New York City, the subways are integral to the daily transportation of its 8.3 million inhabitants. Due to severe overcrowding on existing subway lines in the Big Apple, the city is set to commence two large scale projects to extend the underground network.

The first project will be the extension of east-west Line 7 from Times Square in the east towards 25th Street in the south. The second project is the new construction of the Second Avenue Line from 125th Street in the north to the southern tip of Manhattan.

Due to the existing extensive network of supply lines for water, gas, electricity and data layered beneath the streets of New York, the tunnels for the two lines must be excavated as deeply as possible. Excavation must also cross beneath traffic tunnels, the impact of which must remain as low as possible.

The S-467 and S-468 Herrenknecht Double Shields are excavating the two Line 7 tunnels, with the machines commencing the project in April and June of this year respectively. Both with a diameter of 6.8 m, the two machines worked their way through Manhattan’s hard underground of granite, slate and serpentinite. Construction of the Second Avenue subway has not yet begun; the S-434 Gripper TBM with a diameter of 6.6 m is still under construction. The hard rock machine will excavate two sections of 2.4 and 1.5 km in length respectively.

Phase 1 of the project is expected to be completed by 2015.

In Miami, Florida, the Miami Access Tunnel Project management company has recently awarded a $US654 million contract to French construction company Bouygues Travaux Publics to build a second access road tunnel to the Port of Miami.

The project, which is scheduled to commence mid-2010, will include the construction of two 1.1 km tunnels of 12.3 m diameter and their access roads, as well as the electromechanical engineering for the underground sections and the construction of operational building.

Construction of the road tunnel will be crucial to the development of the Port of Miami which is currently only serviced by a single highway. The new access road will become the principal route for trucks, decongesting downtown Miami by removing the freight traffic now obliged to pass through it.

Meanwhile, underground infrastructure works are currently being planned and organised to help alleviate the immediate effects of earthquakes which frequently rock the California coast.

The San Francisco Public Utilities Commission has just approved the $US250 million New Irvington Tunnel Project as part of the $US4.6 billion Water System Improvement Program.

The project will see the installation of a 5.6 km long seismically-designed tunnel to provide water supplies from the Sierra Nevada Mountains and the Alameda Watershed to Bay Area water distribution systems.

The seismic water tunnel will be excavated using conventional mining methods, including a road header and controlled detonations. The finished horseshoe shaped tunnel will have an internal diameter of approximately 2.5-3.2 m.

The San Francisco Public Utilities Commission has identified the New Irvington Tunnel project as one of the most important projects of the entire system, as it will ensure that 2.5 million inhabitants will have water after a major earthquake.

The tender for the New Irvington Tunnel Project went to bid in November 2009, and construction is due to commence in April 2010. The project is scheduled to be completed by 2014.

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