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Santiago showcase

Rail - Santiago metro in Chile is Balfour Beatty Rail's first break into the South American market. It is battling hard for follow-on work. Report and pictures by Adrian Greeman.

A near trebling of its workforce to more than 1,400 spread over 20 different work fronts and constant reorganisation of access and delivery points is keeping Balfour Beatty on its toes at the new Line Four metro project in the Chilean capital of Santiago.

Even working flat out through the current southern hemisphere winter season it is touch and go whether the project will be completed when it is wanted - by the time of presidential elections at the year end. The present incumbent wants to be able to demonstrate positive achievements to his people.

Chile's economy has been doing well in recent times, driven particularly by huge Chinese demand for copper, Chile's principal export. It means there is something to spend on infrastructure and the presidential battles are partly focused around this issue.

'We shall be at full pelt for at least another eight weeks, ' says Balfour Beatty project director John Latham, who is nevertheless confident that the work can be done. First running of the metro authority's gauging train for the line in late June and electrification of a first 10km or so stretch of track have helped achieve two early milestones for the client, Metro de Santiago, and boosted everyone's morale.

The key problem for Balfour Beatty is getting access. In many places, stations and shafts are still required by contractors, and handovers have been significantly later than scheduled.

For civils the work was split into five main sectors but Balfour Beatty Rail has a single £50M contract for the rail installation on an entire 33km of double tracked line, as well as in two depots. It is also installing 50 turnouts, or points, on the line and 30 in the depots. The final value will be more, once easily agreed claims for acceleration are settled.

Track runs in double line tunnel at the north end of the project for about 9km out from the city centre, then at grade - or 'superficial' - before transferring to viaduct for the 7km run into the important, highly populated, southern districts. After a dip into a final short tunnel stretch, the line resurfaces into an end of line depot.

A separate spur, Line 4A, will carry a second route from the south of the city into the centre, though its lesser priority means this stretch is likely to open next year.

The double track line is being installed as conventional steel wheel on steel track, a departure for Chile which has previously used a rubber tyred vehicle system running on a concrete base with a guide rail - a proprietary Alstom system.

Balfour Beatty won an international tender in conjunction with Brazilian firm John Mendes, which had a local subsidiary in Santiago. But there were some difficult decisions right from the start.

Despite experience in civil engineering and good local knowledge, Mendes was not organised for the logistically demanding task of rail work and Balfour Beatty ended up sending in its own man to take charge.

Then Mendes ran into financial difficulties which forced it to pull out of the project.

Balfour Beatty decided to continue the work alone, taking on some Mendes staff to help with the difficulties of working in an unfamiliar Spanish speaking environment.

Not least of its reasons was to prove something about its abilities in this new continent, says Latham. Although it had not initially been eyeing other projects, there are several major regional rail schemes in the wind which might allow Balfour Beatty to keep up the momentum.

In Santiago the contractor is laying two different types of concrete track slab and installing turnouts, with a track level third rail for the power pickups. The key is logistics, says Latham.

Two types of track have been specified for the system by French design consultant Systra.

A dual booted sleeper system is used in the tunnels and the Vossloh 336 fixing system on viaducts and at grade sections.

The booted system, a VosslohCogefar design, has a short concrete sleeper under each rail, sitting on a resilient pad and surrounded by a rubber boot which is concreted into the main slab.

'The boot removes ground vibration and attenuates the noise, ' says construction manager Mike Bullen, 'but this sleeper system is a little heavier because it requires a greater thickness of slab.' On the viaducts a steel plate fixing is used, creating less load.

Each small, individual metal plate has two bolts set downwards into the concrete within a sleeve insert.

The second is harder to set up, says Bullen, because the individual rails have to be carefully positioned for gauge, taking account of 1/20 wheel inclination on site, overall position, line and height. 'Tolerances for the main parameters are ±1mm, ' says Latham. The twist in the line and an assortment of other parameters also have to be carefully checked.

For the booted sections sleepers are made up in pairs at a production yard Balfour has set up on the edge of the city.

French made Satiba steel moulds are used, with a linking angle bar so that the pairs are already at the right gauge when concreted into position.

Sleepers also have an inbuilt bolting position for the third rail, though on the lighter sections additional fixings are set up and concreted into place as well.

For ficient installation, sequencing of rail welding, fi xings attachment and concreting is vital. Access for materials is a continuous issue, 'and much of your time is taken up checking', says Latham.

Rail comes first. The 60kg/m line is imported from Corus in Wales in short lengths and welded into 400m lengths. 'We do as much as possible with the flash butt unit because this type of weld is best, ' says Latham.

Once in place final connections are formed by alumino-thermic welds, 'but we keep these to a minimum', Latham adds. The kits for this are imported, along with rail grinders and specialist road-rail Mecalac excavators.

One of these was recently airfreighted to Santiago to help keep construction schedules.

Rail and associated fixing are held in position by 'iron horses' while formwork is made up, simple reinforcement for the slab positioned, and concrete poured. Standard readymix is used for the 20m 3 pours, though Latham says a surge in construction activity across the city make it necessary to confirm the orders early and to keep a careful eye on delivered concrete quality.

Larger pours of up to 200m 2 are needed for the turnouts, which are altogether more difficult because of the complexity of the switch blade and crossover elements and the need for accuracy.

'There can be a build up of error from the tolerances in the various elements making up the turnouts, ' says Latham.

Again logistics are critical, with more complex parts to be brought into the tunnel.

So far the client is pleased with progress, according to its project chief Patrizio Vernal Collai. After its baptism on the biggest project of its kind ever undertaken in the country, Balfour Beatty is hoping that more is to come.

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