Along an arc roughly south from Amsterdam to Belgium, six teams are now forming the base for a 300-km-per-hour train service, due to start operations in 2006. Their tools include a tunnel boring machine with the worlds biggest cutting head, at 14.87 meters in diameter. On the sidelines, another construction team is preparing to install track and equipment to complete well over $3 billion of project infrastructure.
BIGGEST Dutch TBM's 14.87-m cutting head is churning through peat, clay and saturated sand. |
(Photo courtesy of Bouygues)
Managing the interface between these two tasks has been "the biggest challenge," says David Gedney, chief exec-utive officer of track and equipment contractor Infraspeed B.V, Zoetermeer. Disparate civil contractors with their own headaches must pull out before Gedneys workers can gain control of the route to complete the system by 2007.
Tensions between the bulk civil engineering work and the following fit-out stem from the contractual separation of those intimately linked pieces of railroad, suggests Bart-Jan Kouwenhoven, a senior manager with the states project company, Projectorganisatie Hogensnelheidslijn-Zuid (HSL-Zuid). "The way [contracts] are structured creates different horizons .We have the role of coordinating all this work," he says.
Contractual novelty arises from the governments unusual procurement approach. Facing budget constraints, HSZ-Zuid adopted private financing for track and equipment, explains project director Wim Knopperts. Needing civil work done first, it fast-tracked those elements by making contractors responsible for design, sewing seeds for later difficulties. "Design-construct for this type of work is not familiar here," says Gert Nederend, managing construction of the lines biggest bridge.
The first design-build contract, for the Green Heart tunnel, went to Paris-based Bouygues S.A., with local support, in late 1999 for $365 million. The remaining five civil bids started above budget by 20%, said a source at the time. But "very difficult negotiations" drove prices down, adds Knopperts. The five civil jobs were finally signed for about $1.6 billion altogether in mid-2000.
After rebidding track and fixed equipment work, also to reduce costs, HSL-Zuid awarded that contract to Infraspeed, in 2001. Owned by U.S.-based Fluor Transportation, Dutch-based Royal BAM NBM N.V., Siemens Nederland N.V. and two U.K. financiers, Infraspeed must finance, design and construct the project in the five years and maintain it for another 25 years.
Fluor, Infraspeeds smallest shareholder, is managing construction. The three contractors, in their own right, jointly have a fixed-price, "date certain" turnkey contract with Infraspeed to deliver the system, worth around $1 billion, says Gedney. The contractors hold 51% of Infraspeed during construction to ensure the bankers dont have "undue influence," he says. Later, the contractors will reduce their stake to 25%.
|BEHIND THE CUTTER Track base is built as TBM advances tp reduce tunnel buoyancy. (Photo courtesy of Bouygues)|
But first, civil engineering must end. Crossing clay and peat ground for the northern two-thirds, the track will run on a piled concrete slab instead of conventional embankments and viaducts. About 170 structures straddle obstacles along the whole route. But the major elements are concentrated in the nations verdant Green Heart area, near Leiden, and also around the wide Hollandsch Diep River, south of Dordrecht.
To preserve the pleasant, windmill-strewn Green Heart, Bouygues, supported by locally based Koop Holding Europe, is building a 9-km-long tunnel, driving the central 7.2 km between cut-and-cover ramps with a huge TBM. Of five short list bidders, Bouygues alone offered a single bore instead of twin tunnels proposed by HSL-Zuid, says project director Joseph Harnois.
The firm wanted to eliminate building mandatory escape cross tunnels between bores, a job requiring tricky ground freezing, says Harnois. At $365 million, Bouygues price undercut its rivals by a large margin, while keeping the job profitable, he adds.
Key to Bouygues single bore is the giant bentonite slurry TBM, weighing over 3,000 tonnes. It must cut through some 12 m of peat and clay at either end and plunge some 35 m down in saturated sand, with pore water pressures up to 3.5 bar, says Frans Vahle, HSL-Zuids tunnel manager.
Frances NFM Technologies, at Le Creusot, supplied the TBM for $35 million, including installation and startup, says machine design manager Gilbert Fantanille. The TBM was the first slurry machine of the 24 NFM built in the last decade, says Fantanille. And it was a big step. "The main bearing is the largest that can be made in Europe. I dont know anywhere in the world that can make a larger one," he says.
The TBMs 110-m-long backup comprises girders spanning between front and rear gantries. Space below allows the railroad track base to be built as the TBM advances, reducing tunnel buoyancy in the groundwater. As well as delivering lining segments, the backup carries precast boxes forming the central equipment gallery under the track floor. Workers ahead of the rear gantry backfill around the gallery. They are followed by teams completing reinforced concrete structures, including the tunnels central dividing wall.
As it advances, the TBM erects nine precast lining segments, plus one keystone per ring. Made by a Bouygues affiliate in Belgium, the segments are generally 60 centimeters thick, 2 m long and weigh 14 tonnes each. Bouygues eliminated positioning bolts with a small plastic roller on each segment effectively slipping into a slot in its neighbor.
In a full days work, Bouygues sets aside four hours for repairs. But at each of three permanent access shafts along the route, the contractor stops for major maintenance including replacing all picks, worn or not. "Maintenance is not to repair, but to ensure there is no problem afterward" explains Harnois.
|HAMMERHEADS Hoisting into place. (Photo courtesy of Bouygues)|
To receive the TBM, Bouygues fills the lower 18 m of the 31-m-dia shafts with a weak sand/cement mix over the base plug. Workers hand-dig an access slot through the mix to expose the cutter head. The most recent stop, at the central shaft, lasted from late this March to early May. A final planned pit stop at the third shaft is set for October, six months before TBM tunneling is due to end.
Having long since completed main design, Bouygues and the owner only recently decided on fire protection. Following several European tunnel disasters, HSL-Zuid wants its lining protected to avoid collapse in the weak sand. Bouygues commissioned trials both for spray-on retardant and polypropylene fibers mixed in the segment, settling for the former.
Harnois seems pleased with progress, though the contract is understood to be about 10 months late for reasons "beyond our control." Difficulties between the owner and affected local authorities contributed. But with the TBM generally advancing "better than forecast even by us," Bouygues is clawing back lost time, says Harnois. Peaking at 22 m in a day, the advance has averaged 16 m, he adds.
Further south, the railroads biggest bridge, at 1.2 km long, must still wait for a fatal accident investigation to end before the three final spans close the Hollandsch Diep River crossing. A man fell to his death in April when a major deck element slipped during installation of a main span box (ENR 5/12 p. 15).
Designed to carry fast, heavy trains on a 2% slope, the bridge has 12, mainly 105-m spans with a continuous single trough deck topped with a 14-m-wide composite concrete slab. The roughly 3-m-deep steel troughs rest on V-shaped pier-top supports of similar dimensions.
The mainly Dutch, six-firm consortium HSL-Drechtse Steden signed the $427 million design-build contract in mid-2000, aiming to complete the bridge next May. Two 2.5-km sunken tube tunnels under the Oude Maas and Dordtsche Kil rivers, plus some 9 km of simple track also form part of the contract.
HSL-Drechtse Steden has design responsibility for the bridge "as long as we stick to the program of requirements," says project manager Nederend. The contractors local designers followed a concept by Van Benthem Crouwel Architekten, Amsterdam, with Arup Group Ltd., London, which won a design competition called by the government in 1998. And it was the cheapest option, says Gaby Schouten, HSL-Zuid's bridge project manager.
Except for concrete piers, all major elements, including nearly 9,000 tonnes of steel, are prefabricated nearby and delivered by river. Precast concrete caissons, each sunk onto large steel piles, support cast-in-place piers. The 25-m- long x 10-m-wide caissons travelled on pontoons before being sunk into place.
Deck steelwork troughs were barged to site in 60-m lengths, with concrete slabs already attached, all weighing some 1,200 tonne. At each pier top "hammerheads" form the deck support and end sections of each span. Hammerheads are 45-m-long box fabrications made integrally with V-shaped supports of similar proportions bearing on the piers.
Too tall to clear overhead obstructions on the boat ride from the fabricators yard, hammerheads travelled to the site on their sides, leaving tops slabs to be cast later on the bridge. With hammerheads in position at either end of a span, a subcontractor attaches hoists to them to raise the intervening 60-m deck section. While hoisting one of the last sections in April, a hammerhead moved fatally for reasons still to be determined.
With bridge site work starting in February 2001, the last hammerhead was due up late this May, eight months after the first. But even before the accident, the contract was running months late, partly because of local authority planning demands and some design changes, says Schouten.
|ON HOLD Fatal probe slows progress. (Photo courtesy of Directie-HSL-Zuid)|
All the problems added to pressure that was already daunting. "I dont say we underestimated, but its been quite a job," comments Nederend. Design took some 35% more effort than planned, he estimates, and substantially more equipment was needed for the bridges erection.
For Infraspeed, the civil contractors tribulations create more anxieties, accentuated by "horizontal interfaces" between civil and equipment work, says Kimmo Oostermeijer, who manages an HSL-Zuid team linking both set of contracts. Given a second chance, all construction would have been integrated in separate packages along the route, adds HSL-Zuids Kouwenhoven.
One problem was the timing of contracts, believes Harnois. "Infraspeed came into the project too late," he says. Because of the time lag between civil and equipment contracts, Infraspeed was initially left working with outdated information, adds Gedney.
Civil contracts began being awarded in early 1999 and designs by the consortia formed the basis of Infraspeeds bid "as of January 2001," he says. While Infraspeed prepared its bid, civil teams continued refining their designs. "When we got on board...we had to go back and take a look at designs as they were being executed and we found some pretty basic changes," adds Gedney.
One resulting mismatch was between bolt holes in ground slabs and Infraspeeds power line supports, says Gedney. So instead of civil contractors casting-in the bolts, Infraspeed must drill in embeds later. "Its big because there are 80,000 embeds," he says. Another clash emerged between fixings for Infraspeeds precast track and the underlying slab rebar.
Seemingly unruffled by tensions in the field, HSL-Zuid director Knopperts says the project is within budget and schedule. HSL-Zuid added nine months to the program two years ago, after hitting land acquisition snags, he says. Trains are due to start in the south in October 2006, with the rest following the next April. Despite the interface irritants, HSL-Zuids Kouwenhoven remains enthralled by the project. "It makes me want to get up every morning and go to work," he says.
he famously flat Dutch countryside is proving to be a difficult platform for one of Europes latest high-speed railroads, now spreading between Amsterdam and the Belgian border. To build the 100-kilometer link, tunneling technology is being stretched to new limits, while soil-like "brown yogurt" combined with complicated contractual boundaries and tragedy on a bridge test Dutch engineering nerve.
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