Tunnelling - global overview

The global recession may have hit the construction but tunnelling activity around the world still seems to be moving - especially in emerging markets. China notably, and to some extent India and smaller countries like Singapore, are making public investments in a bid to counter to the downturn.

The largest stimulus plan as far as construction is concerned is in China, about 75% is US$ 585 million spend is earmarked for infrastructure development.

The country already has many projects on a giant scale such as Shanghai's Pudong-Changxing Island tunnel and bridge project. Traffic began running last November through the twin 7.5 km long main tunnels under the Yangtse river, which were driven by two of the world's largest tunnel boring machines (TBMs) - 15.43 m diameter Herrenknecht Mixshields. Shanghai Tunnel Engineering Corp was in joint venture with France's Bouygues for the project, and the design was by Shanghai Tunnel Engineering Design Institute.

Two more Herrenknecht machines of comparable size completed base drives on a second major Yangtse crossing further inland at Nanjing in August last year. The 14.94 m diameter Mixshield drove through highly water-bearing gravel and silt layers at up to 7.5 bar pressure for a dual-three lane highway link just under 3 km long. Danish consultant Cowi worked on the design which continues construction by contractors, Nanjing Changjiang Tunnel Project company and China Railway 14th Bureau Group.

Shanghai, like many Chinese cities, continues to upgrade its metro system with six new lines completed in the last half year in time for the prestigious international Expo 2010, which opened May 1. The current 420 km system, now the world's longest is due to expand to over 800 km by 2020.

American TBM maker Robbins reports that metros are planned or are underway in dozens of cities, including Guangzhou, Zhengzhou, Xi'an, Chengdu, and Chongqing. China has said CNY 1 trillion (US$ 146 billion) will go to triple the size of its subway system over five years from 940 km to 3000 km.

Some of Robbins earth pressure balance (EPB) TBMs have tunnelled under Guangzhou and Chengdu at record-breaking advance rates. Two 6.3 m diameter machines for the Guangzhou metro excavated 377 m in one month and another 6.3 m machine excavated 458 m in April 2010.

On the same scheme Germany's Herrenknecht has 42 of its EPB TBMs at work plus another six Mixshields, most of which are 6.25 m in diameter. Like Shanghai, Guangzhou's system is being extended for a 2010 event, the November Asian Games, with an additional 134 km of route added.

Two hard rock Robbins TBMs are at work in the giant conurbation of Chongqing which a few years ago became an autonomous city region alongside Beijing and Shanghai. Four more machines are planned for Zhengzhou and Xi'an.

Chengdu, capital of Sichuan, is planning to open its first line this year, a 26.7 km service between Honghuayan and Shiji Square and a second 50.6 km line is underway for Chengdu Metro, a 17.6 km underground section. Seven lines totalling 274 km are to be done by 2035

Robbins has claimed a city record for its 6.26m diameter EPB machine this March, achieving 457.5 m in one month on the second line for contractor China Railway Construction Corporation. Eleven other machines are working in the city in unusual alluvial geology found nowhere else in China, with highly permeable pebbles, sand, and clay.

Meanwhile after five years of construction the country's first undersea tunnel has opened to traffic in southeastern Fujian providing a 8.7 km underground dual-three lane motorway in two 17.5m wide and 13.5m high bores, with a third for maintenance and emergencies. The tunnel cost US$ 469 million to build, and goes to a maximum depth of 70m.

Another major project is the Jinping hydroelectric scheme where difficult ground conditions slowed progress last year for an open type hard rock TBM from Robbins. The 18 km long drives have a 12.4 m diameter and such sizes are vulnerable to rock falls, especially as the marble, limestone, slate and schist of the ground was blockier than expected. A rebuild of the machine's rock support allowed it to be installed closer to cutterhead to provide early support and mitigate against this problem. Herrenknecht also has a 12.4 mm gripper hard rock TBM working on the project.

South in Hong Kong some 26 km of tunnels are needed for the Express Rail Link (XRL) across the border to Guangzhou and Shenzhen tying Hong Kong into China's high-speed rail network. A very tight schedule for eight major contracts will see completion by 2015 of 8 km of 8.2 m diameter TBM drives and another 16 km of drill and blast work.

Drainage scheme

Hong Kong's heavy typhoon rainfall, 2200 mm per year, also demands large bores for its West Drainage Tunnel Scheme on its main island. Work comprises an 11 km long deep tunnel from Tai Hong to Pokfulam, conveying upper catchment storm water to the sea.

The Dragages-Nishimatsu joint venture is building the tunnel in a 4.5 km long, 6.25 m diameter section and a larger 6 km long section of 7.25 m using two Herrenknecht hard rock TBMs, to a tight schedule with completion at the end of 2011. Design is by Ove Arup & Partners Hong Kong.

For some 8 km of smaller drill and blast adits on the scheme two Gia Häggloaders and three Gia locomotives, each pulling three shuttlecars were recently delivered. They will ease work in smaller diameter of the 29 tunnels.

Two other flood schemes are also under way. Contracting joint venture of Maeda, China Railway Engineering company and Seli has just started one of these, a 5.1 km long, 6.5 m internal diameter drive for the Tsuen Wan sewer, using a 7.72m diameter double shield TBM from Seli to get through volcanic tuffs and granidorites.

Nearby, work is just beginning on the 38 km crossing of the Pearl river mouth between Hong Kong and Macau as part of the huge Guanzhou "super-city" area. Though mostly on cable stayed bridge, the scheme also includes the longest immersed tube tunnel in the world, a 5.5 km long section where the route passes near Hong Kong International airport.

Consultants Cowi and the Shanghai Tunnel Design Institute have worked on preliminary design for over a year. Construction begins shortly for completion by 2016.

India

In India large projects include the just completed New Delhi metro expansion with 10 Herrenknecht TBMs extending the subway system in due time for the Commonwealth Games in October.

In Madhya Pradesh state Robbins has supplied the first hybrid TBM it has made, a 10 m diameter hard rock single shield and soft ground EPB, for long sections of 180 MPa rock interspersed with soft clay and gravel. When rock is encountered, the screw conveyor rotates faster to evacuate chips from the cutterhead chamber while in EPB mode it has a greater than 90% efficiency with normal rotation. Cutting tools can be changed from tungsten carbide, special knife-edge bits in soft ground to disc cutters in hard rock.

In Korea last of the huge 180m long immersed tube elements has been placed for the tunnel section of the Busan-Geoje fixed link. The 3.7 km long tunnel at up to 48 m is the deepest immersed tube for road in the world. Immersion in late May just missed the onset of the summer typhoon season, allowing Korean contractor Daewoo Engineering & Construction, leading a seven company consortium, to stay on time for end of year opening.

The deepest immersed tube when it opens will be the Marmaray rail crossing, in Turkey's capital Istanbul, which sits at 58 m under the Bosphorus channel separating Europe and Asia. Last elements were sunk last year but await completion of 9.8 km of bored tunnel approaches either side and 2.5 km of cut and cover, which link it in to a total 76 km of new rail network.

Hitachi-Zosen slurry TBMs on the south side finished drives early this year and a ceremony in April marked completion of 50% of work by Japanese and Turkish joint venture of Taisei, Gama & Nuro. Delays for vital archaeological work on the north side mean a non-stop Europe to Asian railway journey will not happen until 2013.

Far across the Black Sea work is getting up to speed at the Russian resort of Sochi, the location for the 2014 Winter Olympics. In May 2009 Russian Railways started the construction of a first tunnel complex from six eventual projects. It is a 2,25 km combined road and rail link from Adler to the Alpica service mountain resort. An initial 6.18 m diameter service tunnel has been driven over the last year by contractor Bamtonnelstroy using a Lovat TBM through limestone and porphyrites.

The same contractor recently took delivery of three Sandvik ATM105-IC heavy roadheaders for the Olympics work and six Sandvik LH 410 underground loaders (LHDs) featuring a 4. 6m3 capacity side-tipping bucket. Atlas Copco is also supplying equipment to projects in Sochi, including a number of drill rigs and supporting items.

Germany's Herrenknecht is supplying two TBMs for work beginning shortly, a 10.6 m diameter EPB Shield and a 13.2 m single shield, along with a service package for the construction site, including multiservice vehicles, crane facilities, conveyor systems from H&E Logistik, VMT guidance and a segment production plant from Herrenknecht Formwork.

Europe

Europe continues to press ahead with some big projects, notably the three trans-European, alpine high speed rail and freight links, through the Gotthard pass in Switzerland, the Brenner pass in Austria to eastern Italy and the corresponding Lyons to Turin project through the Fréjus pass in France.

The Swiss project, already ten years in the making is most advanced with latest figures showing 95.8% complete of the total of approximately 152 km of shafts, passages and tunnels of the Gotthard Base Tunnel. Some 300 m of difficult drill and blast south from the deep shaft at Sedrun remains and 1.5 km to go on the remaining TBM drive with breakthrough and total completion of the 57 km base tunnel expected in October. Fitting out will take almost a decade more.

This spring work also started on initial drill and blast of the 15.4 km long Ceneri base tunnel from portal at both end which have been under construction for the last year. The tunnel continues the Alptransit line south of Gotthard.

At the 55 km Brenner Base Tunnel, Austrian client BBT says it has completed 8 km from 11 km of the first 6.7 m diameter exploratory tunnel contract on the Italian side through so far excellent granite. Work has also begun now from the Austrian Tirol north end with 300 m drill and blast through quartz and schists complete of an initial 5 km contract with contractors Arge, Strabag and Porr. The 9.5 m diameter main drives are due to start in 2013.

In France the difficult 6 km long St-Martin-la-Porte exploratory tunnel should finally complete in June and a first exploration is beginning on the Italian side. A go-ahead on the main tunnel is due by 2013.

The US still has some big projects, with a start imminent for the reconditioned Robbins TBM on the long awaited first phase of the Second Avenue Subway line in New York. It will head from 92^nd to 63^rd Street southwards.

Another major project just beginning is the US$ 8.7 billion Mass Transit Tunnel, a second railway crossing on the west side of Manhattan at the level of the 100 year old rail tunnel connection from New Jersey into Penn Street Station at 34th Street. The first Manhattan side 1.6 km section was let last year under a US$ 583 million contract to a joint venture of Barnard and Judlau Contracting. A second section, Palisades on the New Jersey side, also about 1.6 km long, has been given notice to proceed and bids for the underwater section are expected in the autumn.

The North America continent also sees major works gathering pace in Mexico City where the giant 62 km Emisor Oriente flood relief sewer has got three Herrenknecht TBMs working already on respectively on 10 km, and 11.5 km and 12 km drives, all just under 9 m in diameter. Three more machines, from the Robbins are in transit this spring from Texas for assembly in starter shafts just being completed for the other three drives on the project.

Robbins also has a 10.2m diameter EPB at work on the 24 km long Line 12, or "Gold Line", for the Mexican Federal District's first new metro line in ten years. It is working in cover as little as 7.5m in the extraordinary mixed volcanic tuff, gravels and boulders and soft clay. In May 2010, the machine had reached the 300 m mark.

Finally Abnormal Load Services (International) from the UK has just delivered an 7.8m diameter EPB from Lovat in Canada to Argentina. The machine is for construction of the Arroyo Maldonado flood relief tunnel in Buenos Aires.

Busy, busy, busy

So while the tough economic times are hitting the construction industry as a whole, the tunnelling sector is showing few signs of slowing down. This may be because projects are so large and complicated, they haven't had a chance yet - the slowdown may be years down the line as public budgets get squeezed. But for now the sector is as busy and ambitious as ever.