Phase two of the East Kent Access Improvement Scheme is the biggest highway project ever undertaken by Kent County Council. It will provide 8km (five miles) of dual carriageway around the Isle of Thanet reducing traffic congestion, providing journey time reliability improving connectivity with the ports of Dover, Ramsgate and Kent International Airport.
The opening of the new dual carriageway on the 23rd May 2012 was achieved five months ahead of schedule. More than 2,500 people were involved in the construction of this contract and over 1,250,000 man hours worked.
At the heart of this project was the innovative design and build of two key structures, the underpass at Cliffsend and the over-rail bridge at Cottington Road.
This unique design and build element was to deliver a cavernous ‘tunnel' beneath a major railway line that intersected with a road level crossing at Cliffsend Village. At 25m wide, 6m high and 126m long. The underpass was constructed with its roof 6m below the railway line, sitting in a 15m deep cutting either side of the railway.
Box jacking is a well-tested technique for building tunnels and underpasses as it has minimal impact on the existing road and rail infrastructure. The underpass constructed on this contract is believed to be the most impressive example of jacking within the last decade and at over 126m long, the longest jacked structure in the world.
In order to construct the underpass six box sections with individual masses of 2,500 tonnes were cast on site and installed using hydraulic jacks delivering forces of up to force of 350,000kN. In tandem with the jacking process the ground immediately in front and beneath the box sections were carefully excavated and removed.
Constructed during night possessions, this two-span concrete integral bridge, carrying the new dual carriageway, was built over Network Rail's channel tunnel rail link, local high speed rail infrastructure and a local road. The reinforced concrete structure was constructed on piled foundations behind a safety screen to address the soft ground conditions.
This project has completed improvements on the A299 Thanet Way and A256 that were started in the 1980's.