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High speed, low profile

Technical feature Taiwan rail

In Taiwan, the most concentrated force of railway expertise in the world is busy designing, inspecting, checking and controlling a huge new high-speed railway - and no-one has noticed. Adrian Greeman reports.

'This is one of the world's biggest construction projects, ' points out Michael Baxter, chief director of trackwork for Taiwan High Speed Railway Corporation.

Total cost for the railway and its systems is NT-446.4bn, which translates into around £8.9bn, the price of a Channel Tunnel.

And that figure excludes land which is supplied by the government for the 35 year build, operate, transfer concession.

'We are also doing it fast, ' emphasises KH Lee, one time controller of airport projects in Hong Kong and now as senior vice president, in charge of all construction management for THSRC, concessionaire for the scheme. It is made up from major Taiwanese conglomerates and banks.

'How many single city metro lines would be done in five years? We are building 345km of high speed railway to be operational by the end of 2005, ' says Lee.

Civils work began in March 2000 when the first of a dozen huge design and build contracts were let, ranging from £200M to £400M. Two British engineers, Peter Humphries in the north and Jeff Hewitt in the south, head up twin regional offices that oversee the international joint ventures and keep them on time and to quality.

Building the line is no easy matter. It must thread its way through the densely populated coastal plain on the west of the island and through hilly ground in the north. Much of Taiwan is mountainous and 95% of its 24M people live on a small coastal strip on the island's west side.

Road and rail corridors use viaduct to minimise expensive land take. Some 242km of the new line will sit 5m to 25m high, while another 48km in the north will disappear into numerous 14m wide twin track tunnels, some very difficult to build.

The project's longest tunnel is the Pakuashan at 7,360m through dry compacted sands gravels and cobbles, where Germany's Bilfinger & Berger is making good progress.

Japan's Obayashi further north has the difficult Hukou, a 'mere' 4.3km long but in saturated soft ground which at times is very hard going.

Tunnels are all using variations of soft-ground NATM. Up to 40m cuttings and embankment make up the route.

Viaduct sections have another function, keeping line above Taiwan's summer floods when typhoons can dump up to 800mm of rain in a day on to the 4,000m high mountains.

But Taiwan is also highly seismic, the result of a complex three way tectonic collision between the Eurasian Plate and the Philippine Sea Plate. The geological battle means frequent earthquakes, like the devastating 7.8 Richter scale event of September 1999.

Elevated structures must be heavy, solid and well founded.

Design codes follow Californian practice with heavy spiral reinforcement-wrapping for containment in columns, for example, says Jeder Hseih, assistant vice president of the THSRC construction management division.

Unfortunately too, for most of the southern route firm ground is hard to find. The coastal plain comprises mountain erosion. In the north there is gravel, sands, cobbles and conglomerates and short piles or spread footings serve for most piers.

But in the southern half of the route there is only soft clay and silt, a 'slop' that supports no end bearing piles. The top 20m of ground can liquefy too, so structures require huge friction piles, usually 70m long and up to 100m with diameters at least 1.5m.

On one typical contract, 5,000 piles must go in along a 35km route and altogether the project uses 30,000. Surprisingly this huge demand for rigs has not caused a bottleneck, says Hewitt, chief director for the southern regional office. 'Rail work coincided with a downturn elsewhere, ' he explains.

Many contracts are now reaching superstructure and with so much to be done, contractors are using factory methods. Most have opted to make usually 3.5m deep box beams as precast units and launch them by gantry on to pier tops.

'This is not untried engineering but rigs can be pretty impressive, ' says Hewitt's counterpart on the Regional Office North, Peter Humphreys. 'The project has an unprecedented use of full span launching.'

'Most contracts use a single precast yard, delivering up to 800t beams for launching up to 12km away.

'We also have cast-in-place formwork on the south end contracts where track must finish early, ' says Hewitt. 'The THSRC will use that section for tests and training on rolling stock.'

Insitu concrete is slower but gives more programme flexibility because precast units must wait on completion of special spans and various bridge crossings of up to 150m for rivers and roads. Some contractors have made late starts on site and extra insitu shuttering rigs mean they can now catch up.

Hewitt and Humphries think contractors underestimated time needed for design and checking before site work began, particularly with stringent seismic requirements.

Procedures are complex and contractors need their own design consultants as well as quality and checking engineers to certify drawings.

These are monitored by the THSRC teams drawn largely from international metro and rail projects of the last two decades, from Singapore, Hong Kong MTR and the Channel Tunnel.

All designs are further independently audited by a government appointed engineer, the International Railway Engineering Group, led by UK firm Mott MacDonald. Boxes and boxes of design drawings have to be signed off at various levels.

'Contractors also have to organise some pretty huge site works with numerous 'faces', ' Humphries adds. 'The sheer scale of the job is impressive; on our longest 41km contract alone we have 60 workpoints. Getting around country roads is difficult too.'

Conventional inspection is impossible he says, even with some 50 or 60 staff on each job and another 60 at the headquarters. But self-certification 'is working rather better than I though it would, especially as it is new to Taiwan'.

Contracts are stringent with the contractor taking much of the risk including unforseen ground, government legislative changes and negotiating with authorities for design agreement and construction access.

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