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Making waves

Highways - Ground penetrating radar is saving time for highway engineers in the north west.Bernadette Redfern finds out more.

In the old days ground penetrating radar (GPR) used to mean lots of cones and lights and a Landrover being driven at 5mph. It required lots of pre-planning and was just as disruptive as coring, ' says GPR expert and managing director at Aperio systems, John Baston-Pitt. 'But now we can move at traffic speed without any need for lane closures and take measurements every 0.5m. Computers are faster now, we used to get a scan every 32 seconds whereas now we can take 400 in a single second, ' he explains.

The vehicle borne equipment uses radar to measure the thickness of the bound layers of the road surface and this data is then used to create a profile of the highway.

'The thickness of the road surface has a huge impact on the stiffness of the road.

Knowing the thickness of the bound layer and the traffic loading allows us to calculate the 'stiffness and hence the surface design life, ' says Atkins Area 10 road renewals team leader Paul Chambers.

Chambers heads up the Atkins design team on the Highways Agency framework for Area 10, which stretches from the M6 in Staffordshire up to Preston and includes the M62 all the way into Yorkshire. Within the next month Aperio Technologies will have a profile of every single road stored in its database. 'We have profiled 70% of Area 10 and intend to have mapped the final 30% by the end of the month, ' says Baston-Pitt.

'Rather than having to set up coring trials every time a surface needs repair we can just dip into the database, ' says Chambers.

'It is really useful on sliproads, as to take cores requires a closure and it takes 12 weeks to get approval, ' says Chambers.

The availability of up to date information on the road surfaces is beginning to show real benefits. 'We can use the GPR information to produce much more accurate deflection data and develop more innovative solutions than we would otherwise be able to implement, ' says Chambers. An example of this is the A550, which runs between the Wirral and North Wales.

'Initially our coring data told us that the road surface was variable, with some areas better than others, so we were proposing to replace the entire 5km stretch. But when we reprocessed the information using GPR we could more accurately predict which parts of the road surface needed to be recycled, rather than doing all of it, ' he explains.

The ighways gency maintains archives of road construction but can lack details of maintenance and upgrade work done since the road was built.

Although Area 10 will be the first areas of the country to be fully profiled, Aperio is busy collecting data for other areas and has recently begun working with local authorities.

Southampton City Council is acquiring GPR construction data for its A and B roads and all principal roads within the city and says that the construction information from the extracts eliminates the need to take extra cores, as well as avoiding extra trial pits and so reducing roadworks.

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