The theme of this year’s International Tunnelling Association (ITA) Congress at Durban, South Africa "Tunnels under Pressure" was imaginatively appropriate. Not only did this refer to the high rock pressures experienced in the deep mines of that country and perhaps now in rail "base tunnels" in Europe and in the Andes but also to many other pressures on the industry. Economic pressures hanging on from the Asian crisis were supplmented by political pressures, environmental pressures and those of pubic expectation. During the year there have been too many headlines of the wrong type for comfort, such as the aftermath of fires in the Mont Blanc and Tauern tunnels, continued ground difficulties in many tunnels such as Hong Kong’ strategic sewage disposal scheme and cost overruns on large projects like London’s Jubilee Line Extension and Boston’s Central Artery/Tunnel.
The HSE report on the London Heathrow Airport collapse (see News) may reawaken arguments about NATM and/or "sprayed concrete lining" (scl).
Good news sis always more muted. But examples inlcude completion of the longest road tunnel in the world in Laerdal Norway), and largest diameter tunnel bore for the fourth Elbe tunnel in Hamburg. The impressive Øresund Link in Scandinavia opened the first solid link to Europe since the Ice Age.
In Switzerland and the UK financial go-aheads have come for much needed major tunnelling for Alptransit and the Channel Tunnel Rail Link. Extensions to the Madrid Metro show that underground construction can be completed not only time but also on budget. Many sewer projects to eliminate uncontrolled discharges are combating pollution.
Even more encouraging determination to tackle earlier difficulties. At the American Underground Construction Association (AUA) conference in Boston themes were "lessons learned" and planning for risks of all types in advance.
The industry is perhaps starting to recover from a difficult period. A brief look at last year’s major news highlights triumphs over difficulties.
Asia
The Asian market has provided some excellent examples though also continuing problems.
The determination of the Chinese authorities to push forward massive transport and hydropower tunnel projects is one major feature.An eventual success story was completion of tunnelling on the 18.5km Qinling link last August (T&TI October 1999 and T&TI December 1999 ). Wirth TBMs used were the largest employed in China at the time and were then refurbished for work on a 19km-long tunnel on the Nanging-Xian railway. Drill-and-blast excavation for tube two, completed March 1998, was the fastest d&b in China.
In the hydropower sector, construction of the Wangjiazhi Yellow River Diversion project continues in a scheme to supply water to arid provinces.
Much to the relief of many foreign participants, construction activity in the Hong Kong SAR continues at a high level with the continued emphasis on new rail work, although water supply and sewerage also form significant segments of the market.
In February we reported on another exotic Japanese tunnelling machines, this time by NKK, to be used on the Honcho tunnel of the Yokohama Metro. The 432m-long twin-bore route will be excavated in one direction by the NKK DPLEX shield-machine which will then be turned around for the down-line drive. The metro line is due for service in 2003.
In common with China, the construction programme in Singapore has continued with public investment. Design work has begun on the massive Deep Tunnels Sewer Scheme, and construction of the North-East mass transit line continues, including a technically challenging extension to Changi Airport.
Europe
One of the major successes of the European tunnelling year has been the breakthrough of the world’s largest diameter (14.2m) TBM, an innovative Herrenknecht Mixshield called "Trudi", on the fourth tunnel under the River Elbe in Hamburg (T&TI April 1999).The reusability of even such an unusual machine is shown by planned refurbishment for an motorway tunnel in Moscow.
Another milestone project completed was the Laerdal Tunnel in northern Norway despite a collapse in June 1999. The Laerdal is claimed to be the longest sub-sea highway tunnel in the world. Norway has been keen to employ its North Sea oil revenue to improve links to remote areas.
Work has begun on Europe’s next mega-project, or projects, on the Alptransit scheme. The largest of four construction contract packages on the Lötschberg tunnel was awarded in February (T&TI May) to a jv of Ilbau, Walo Bertschinger, Dumez-GTM and Skanska for $347M. Work was scheduled to begin last month for completion by February 2006. Unusually nowadays work will be entirely drill-and-blast.
However, plenty of drill-and-blast work is in prospect for the $953.5M Botnia Rail Line project in northern Sweden (T&TI March). Lemminkäinen of Finland won one of the first contracts in 30km of tunnels in the 1.1km-long Kalidal Tunnel. Also in Sweden the world’s first steel-lined rock cavern (LRC) is being constructed at Halmstad in the south of the country for gas storage (T&TI M ay). Excavation of the domed cavern was carried out by spiral tunnels and ramps.
In the UK most interest focussed on phase two of the Channel Tunnel Rail Link (CTRL). Contracting jvs were invited to tender for five underground construction contracts in this phase (T&TI June) worth a total of $960M. Awards are expected early next year. Water services continued to provide "bread-and-butter" tunnelling work in the UK although as pollution control standards are achieved, this is likely to tail off.
Despite an economic downturn, Germany sustains a high level of tunnelling activity with the emphasis on rail. One city to benefit is Düsseldorf (T&TI June) with a new metro line using an innovative cam-and-pocket concrete lining segment joint.
North America
In the US, despite being the home of free enterprise, most tunnelling work depends on federal funding. The City of Boston is again the focus of tunnelling activity this year with major projects for transport, water supply and wastewater.
The Central Artery/Tunnel Project has been under attack for cost overruns to some extent due to a difficult urban route, predominantly soft "made" ground, and the need to maintain existing services and transport routes. For the tunnelling engineer there are many interesting aspects including the use of "stacked drift" construction to support existing structures, and the use of immersed tube elements, ground freezing, box jacking, soil stabilisation and open cut work.
In June T&T North America focussed on the growing demand for water, and tunnels to transport it, forecast to exceed that for transport. Current major US water schemes include the Inland Feeder project in California, the Lake Mead tap in Nevada (T&TI January) and the New York City water supply tunnels, with the San Diego to San Francisco water project in design.
Continued efforts to control construction costs in the US have resulted in the adoption of design-and-construct practices for five demonstration projects backed by the Federal Transportation Administration (T&TI North America November 1999). The five projects are the Tren Urbano in San Juan, Puerto Rico, now reaching completion, the BART system extension to San Francisco Airport, Baltimore light rail extensions, the Hudson-Bergen light-rail system in New Jersey and the Union Station terminal project in Los Angeles. Of these the Tren Urbano and BART projects feature significant underground work.
Other urban rail projects being planned with tunnels for US cities include those in Seattle and Miami.
In Canada excavation of the Toronto Sheppard Subway Twin Tunnels has been completed (T&TI January) and increased sewerage work is planned for Edmonton, Alberta.
South America
Widely differing economic fortunes between Latin American countries, and political situations within them, continued to make work difficult in many of them this year. Nevertheless, success stories were there including the completion of a new water supply tunnel for Buenos Aires, Argentina (T&TI March). Using two Herrenknecht TBMs, the Wayss u Freytag/Soliazzo Hnos jv completed the 15km-long bore in four drives.
Despite its relatively serious economic difficulties, Japan continues to provide a high level of foreign aid finance for projects in South America and elsewhere, especially for hydropower. The OECD is funding the $304M Yuncan Hydropower Scheme in Peru. Work began last year (T&TI September 1999) on a 26km long tunnel by a jv of Skanska Internatonal, Cosapi of Peru and Chizaki of Japan. Seven of the nine tunnel drives are being excavated by drill-and-blast and two TBMs are being used for the remaining two.
Metro schemes across the region are making slow but steady progress including the collapse-troubled Sao Paulo Metro. Also in Brazil a technical and economic feasibility study has been completed for Line 3 of the Rio de Janiero Metro. The $665M project includes a 4km tunnel.
Africa
Beset by long-term economic problems and escalating health concerns, the governments of Africa have few chances for underground construction except in mining. Notable current exceptions are the Lesotho Highlands water scheme and the metro and wastewater projects in Cairo. Water services, with some large city transport, is likely to dominate any future work. Even on the tiny island of La Réunion water tunnels are under construction using TBMs.
Corruption cases have overshadowed the technical achievements of the Lesotho Highlands Water project(T&TI February and July) .
On the Cairo Metro the final 3km section of Line 2 is due for completion at the end of the year, while plans have been made for the east-west Line 3 to interchange with both Lines 1 and 2.
Two irrigation water tunnels in Swaziland were completed in 1999. One was 386m long and the other 460m, part of the Maguga Dam scheme to aid sugar cane farming in Swaziland and South Africa (T&TI September 1999).
Australasia
Tunnelling work associated with the Sydney Olympics reached completion this year, although there are a substantial number of other projects in progress in Australia for sewerage, rail and highways. Sydney Water, the client and sponsor for the Northside Storage Project, was accused of deliberately underestimating the cost of construction in order to obtain state government support (T&TI April). The original estimate of US$234M has risen by nearly US$50M. The scheme is designed to limit pollution of Sydney Harbour.
Elsewhere the major project is the second Manapouri hydropower tailrace tunnel, which hit geological difficulties despite the proximity of the first tunnel and its known geology during construction. Protracted legal proceedings were predicted (T&TI April) due to liquidated damages against the contracting jv of Fletcher Construction (NZ), Dillingham (US) and Ilbau (Austria).
Future work
Many projects are conceived many years before construction actually takes place, even if technically feasible. So it was with the Channel Tunnel that was eventually built after 150 years to be recognised as one of the worldís greatest construction projects. In February last year T&TI reported on two proposals by Eurotunnel for a second fixed link declared to be technically feasible (one a road tunnel) but "long term" . The proposals were to meet Eurotunnel’s concession obligations and, according to Eurotunnel executive chairman Patrick Ponsolle, would only be embarked upon if such a venture "would enhance the profitability of the company and was in the interest of the shareholders".
More realistically there are still major programmes to be continued in Asia, to some extent in Europe, and also in North America as it emerges from a relative slump in tunnelling activity.
Major transport projects, preferably be self-financing, will continue to provide welcome but intermittent work for the underground construction industry. However perhaps in the long term it is meeting unavoidable human needs that most future work will be generated.
The need for water transfer for development and prevent disasters has been reported on (see above). Other unavoidable needs could include wastewater schemes for disease prevention and pollution control and urban mass transit. Both of these relate mainly to the new mega-cities.
Affordable hydropower schemes will continue to attract investment in cheaper, sustainable energy if environmental concerns about any reservoirs can be met.
