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Scotland on the move

GEOSYNTHETICS

Boom times in construction north of the Border means increased demand for geosynthetics, particularly on transport projects. Gareth Beazant reports.

Edinburgh airport has seen steady expansion since it was opened by the Queen in 1977. It started life as a First World War aerodrome and later became RAF Turnhouse. The Scottish capital's popularity as a tourist destination means its airport is now one of the busiest in the UK.

In the latest expansion, BAA has partnered Amec Construction to form the pavement and infrastructure team to build and manage parallel taxiways to improve operations at the bustling airport.

The high loads imposed by aeroplanes require a structured layered system of foundations and Amec worked closely with engineer Babtie for the design.

In the end, a Maccaferri geogrid was specified to rest at the bottom, overlain with a 700mm capping layer. There is then a slim layer of terram and a 150mm strip of what is locally known as 'blaes', a by-product of local mines.

At the top there is a 150mm layer of lean concrete with 420mm of pavement quality concrete capping the structure.

In one of its biggest supply projects in Scotland, Maccaferri delivered 66,000m2 its Enkagrid Max geogrid with a load rating of 30kN to act as the base layer for the foundations. The biaxial geogrid is made of extruded polypropylene bars and is a Colbond material.

The route of the taxiways is to 22m wide in places and suitable overlaps of the 5m wide by 100m long rolls of geogrid have been ensured.

Enabling works began in October 2003, and the project is expected to be complete by late December 2004. It marks a busy time north of the border for Maccaferri.

'It's quite unusual to have so many large projects in Scotland, ' explains Scott Harvey, the area sales engineer.

'Perhaps it's because building is taking place in smaller sites and people are using steeper slopes. And a lot has been invested in the roads recently.'

A booming housing market means more demand for Maccaferri gabion walls for which it has its own construction team to design and supplies.

Royal Bank of Scotland HQ

The new world headquarters of the Royal Bank of Scotland is one of the largest projects in Edinburgh. At peak times almost 2,000 workers are involved on the project in the Gogarburn district of the city. The site covers 32ha and will accommodate 3,250 staff in 32,500m2 of office space.

This impending population explosion requires a host of transport provisions. The most dramatic is a slip road that loops off the A8 motorway on to a flyover to the new office on the other side of the road. It will also act as a pedestrian bridge and cycle route.

The loop, now being built, includes a steep reinforced earth embankment. Maccaferri is supplying its Enkagrid Pro with a load rating of 60kN for the main part of the embankment. The uniaxial geogrid of extruded polyester bars is being used with a Type 1 fill material to build up the embankment, which will be up to 8m high.

The typically harsh Scottish weather meant plans had to be made for ensuring the grass layer of the embankment would survive the winter. 'It's very open here and strong winds could have blown the vegetation layer seeds away, ' explains Scott Harvey, sales engineer at Maccaferri.

'A biodegradable coconut fibre product (coir) has been used to hold the soil. This will biodegrade in one or two years when the grass layer has fully grown.'

Maccaferri sought approval from the Scottish Environment Protection Agency to use the Type 1 fill and the coconut material, which was granted, and discussed ways to ensure that the potential run-off into watercourses was not contaminated.

Main contractor Crummock Construction called on Maccaferri for the design and supply of the materials because it is one of the first such embankments Crummock has been involved with.

The two companies claim that value engineering halved the quantity of Enkagrid Pro needed to about 30,000m 2. Mace is project and construction manager for the development and WSP is the engineer.

The new headquarters is expected to open in 2006.

A80 accident spot improved

Auchenkilns roundabout on the A80 is the blight of many roadusers on the journey between Glasgow and Stirling. The roundabout causes massive tailbacks and there are many accidents.

All this is about to change. The notorious main roundabout will be removed and through traffic will be able to sail over the spot on a new flyover. Slip roads will connect to two new roundabouts either side of the A80.

But main contractor AWG has had to cope with very poor ground conditions. Up to 7m of 'boggish peat' means piled embankments will be needed, but the ground must be strengthened before a piling rig can go anywhere near it.

The solution is a temporary pile platform supplied by Maccaferri. A layer of a highstrength 150S geotextile has been used to span the areas where the piling rig will be needed.

About 25,000m2 of the geotextile has been required for the two stretches of around 150m long. The area was extended to allow haulage vehicles access to the sites.

Stent has been awarded the piling contract and will drive precast concrete piles through the geosynthetic to depths of about 12m.

The company has begun on four to five weeks of piling for an embankment of 7m for two twolane slip roads.

The £22M project is being funded by the Scottish Executive.

Work started in January and is expected to be complete in summer 2005.

'This is a major investment of both local and national interests, removing one of the major congestion points in the central Scotland trunk road network, ' said Nicol Stephen, Scottish Executive Transport Minister.

'This will be good for local communities and good for the Scottish economy. The environmental and road safety benefits will be significant.'

Maccaferri has also secured the contract for the permanent works for the embankments.

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