Major civils works on Holland's high speed rail line are almost complete.
Mark Hansford reports from Rotterdam on construction of the one missing element.
Building the 100km long high speed rail line linking Amsterdam with Antwerp has thrown up more civil engineering challenges than many anticipated. Since work began in 1999 engineers have set about driving the world's biggest bored tunnel - 14.87m in diameter and driven 7km under Groene Hart, or the 'green heart of Holland' (NCE 31 January 2002), not to mention constructing two 2.5km long immersed tube tunnels and a 1.2km long multi-span bridge (see box).
So it is slightly ironic that one of the last sections to be completed will be an apparently simple 19.5km section across open country between Rotterdam and Zoetermeer. This is cluster three, 'Zuid-Holland Midden' (ZHM - South Holland Middle), one of six design and build contracts that make up the civils works on the high speed line. It is being carried out by the HSL-Combinatie Zuid-Holland Midden consortium, made up of BAM Civiel and Heijmans.
Simplicity is relative, however. 'We are building on a dried out swamp and the ground is very unstable. The track is designed for 300km/h trains and will be in use for 100 years at least - it has to remain stable, ' says ZHM project manager Piet Zuidgeest. The 20km section actually calls for four distinct types of construction.
Heading north from Rotterdam, a 4km cut and cover tunnel prevents high speed trains interfering with operations at Rotterdam Airport and ensures that land immediately north of the city can still be used for development. The only real complications here have been poor ground and the high water table, which hovers at or near ground level -not unusual in Holland.
To overcome ground conditions most of this tunnel is made with temporary sheetpile walls and founded on 25m deep piles.
To prevent water pressure interfering with casting of the construction concrete a 1m thick concrete floor is being placed by divers. In total, 80,000m 3of underwater concrete will be poured.
Construction of the cut and cover tunnel section has been complicated by a ban on cranes and tall piling rigs near Rotterdam airport. To construct the tunnel walls here reinforced concrete diaphragm walls have been used in place of sheet or contiguous bored piling.
Cut and cover tunnelling is now largely complete. From the airport the line will remain largely out of sight for 4km thanks to the construction of a concrete-lined U box cutting, built in the same way as the tunnel, bar the roof. A late change in 2001 by the client to further lower and re-engineer the U-box cutting following pressure by the public, made the whole programme slip nine months.
The line will finally emerge above ground as it enters Holland's famed glasshouse heartland near Bleiswijk. Here it will run for 6km on an elevated section of track carried on pylons.
Most of these will be at 17.5m centres and carry the line 6m above ground level to allow for future land development and road construction.
'It's functional transparency, ' says Zuidgeest. 'We can't predict what people will want to build in the future and the way we've designed it, you can put a road through every gap.'
But having the line so visible has caused ZHM a big headache, with planning squabbles holding up construction.
Dealing with planning issues has been a major new experience for Zuidgeest. Gaining planning permission from the local authorities was the client's responsibility, he explains. The contractor's programme was heavily influenced by these issues. 'Usually we get to a site, put a fence around it, make some noise and go. But over the 20km we're working on there are 1,000 activities that need permission.
As contractors we are not used to all this public contact.'
Objections were raised over the 1km long elevated section north of the A12 motorway crossing. This called for a hasty rethink, as it was planned to build the deck insitu with one team operating each side of the motorway crossing. 'The dispute on the north side held up our planning. So we had to put all our resource on the south side and do that first, ' says Zuidgeest.
'We are now working on the north side.'
And at some rate. Two teams are turning out two 35m sections a week using an innovative 'walking factory', a giant falsework and formwork system that allows the viaduct deck to be built insitu but with all the quality and speed of precast construction.
The deck has three prestressed longitudinal beams which, with the floor slab, form a W-profile structure. It is formed by walking, or more accurately sliding, the lower half of the factory into place by two portal cranes that run the length of the site. It is then clamped to the cast-insitu pylons and jacked into position.
Prefabricated rebar cages and cable ducts are positioned and locked into place by the top section of the factory. Setting up the formwork and rebar takes just three days and the concrete is poured in a single day.
Striking the formwork is a simple reverse operation, in which cranes lift the top section away before the jacks lower the bottom section.
The final 4.5km is a straightforward, settlement-free slab, construction of which is now largely complete. Overall, ZHM is working to a deadline of 14 February 2005 to be ready for the track-laying contractor, with a year on top of that to apply finishing touches.
How it works
Dutch High Speed Line untangled: who's who, what's what and why.
Construction and operation of the 100km Dutch High speed line is a curious mix of traditional design and build and public private finance.
Client for the job is Projectbureau HSL Zuid, part of the Dutch ministry of transport, public works and water management.
The Dutch government announced its plans for the link in 1998. So that work would not be held up on finance it opted to let the £2.57bn civils works as six geographically arranged 'clusters', all lump sum design and build. The HSL-Combinatie Zuid-Holland Midden consortium is tackling cluster three.
Awarding civils contracts as design and build outside the PPP enabled the government to take on major risks such as ground conditions, and explosive ordnance investigation and clearance itself, reducing the contract price.
The job of civils contractors is simply to leave a concrete shell on which track, signalling and overhead line electrification can be installed under a PPP deal. This shell is guaranteed for five years, with a further five-year defects correction period, giving assurance to banks. Having the civils substructure built independently of track and signalling and designed for a 100 year life means that it would be a relatively painless process to install a new state of the art track system, should one come along, so keeping the line at the cutting edge of rail travel.
Installing track and signalling will cost £900,000, financed by a public private partnership SPV Infraspeed. Infraspeed consists of Fluor Daniel, Royal BAM Group, Siemens and a series of banks. BAM is the parent company of UK firms Edmund Nuttall and HBG Construction.
Infraspeed signed a 30 year deal with the Dutch government in June 2001. This is split into a five year construction period and 25 years operation.
Infraspeed will be paid an annual performance fee of around £125M in return for 99% availability.
Construction of the track falls to BAM. It will use an embedded rail system for all but 5km near the Belgian border where it will use traditional ballasted track. BAM will also erect noise attenuation barriers and security fences.
Overhead line, catenary poles, signalling, communications and power supply will all be provided by Siemens. Signalling will be to the European standard for interoperability, ERTMS. Fluor Daniel is carrying out programme management.
Track and signalling works are now ready to begin, and will accelerate as the civils contracts finish. BAM believes it can lay up to 300m of slabtrack a day.
Construction of 5km of test track in cluster one near Amsterdam will begin in May. Full construction begins in August on sections to the north and south and through the Groene Hart.
The line will then be ready in two stages - the south section opening in April 2006 and the north later the same year. Netherlands Railways and Dutch Airline KLM signed a deal in 2001 to operate services on the line and have formed a new company for this purpose.
And it has to be ready as the financial ramifications would be serious, says Infraspeed contract manager Robert Bos. 'The start date is cast in stone, and on day one we start paying back our loan. It is very important we have that fee for availability.'
During the construction phase risk is shared pro-rata, with BAM taking 43%, Siemens 46% and Fluor 11%. But if one party alone can be proved to be at fault, it will be solely liable. Once into the 25 year maintenance period the same pro-rata risk and reward are shared.