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TENSAR TEMPORARY SACRIFICE HELPS COMPLETE MISSING LINK
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Along the Dishforth to Leeming section of the North Yorkshire A1 upgrade, new carriageways are being built adjacent to the in-use existing highway. By using a Tensartech TR2 Wall solution to create a temporary structure while raising a below grade section, the Carillion/ Morgan Sindall joint venture contractors are saving extensive time and helping to minimise traffic disruption.
The existing 150 metres section of the A1 either side of the Butcher House Bridge is up to 10 metres below the final required grade of the new motorway. An earth retaining structure with a near vertical face was required to support the new carriageway, which would allow the traffic to be switched to it while the old section was filled in and complete the dual three lane motorway.
The conventional technique using extensive sheet piling along the embankment and for the bridge abutments to relieve lateral thrust would have been time consuming, and access for the installation plant could have disrupted traffic flow. In addition, the sheet piling would have been buried when the carriageway was filled in for the completed motorway, making a very expensive loss of material.
“Tensar developed a reinforced earth solution which was quick to install, with minimal disturbance to vehicles by temporarily supporting the new south bound embankment, bridge wing walls and abutments,” commented the joint venture senior engineer, Kevin Wilcock. “As a temporary sacrificial structure, the TR2 was by far the best option and less expensive than other methods available.”
The Tensartech TR2 solution comprised compacted fill reinforced with layers of Tensar’s uniaxial geogrid, securely connected to steel mesh facing units to form a 100m length of the 85°earth retaining structure up to 3m high; site won fill was used for this section. For the bridge abutments and wing walls, a 26 m length of vertical faced TR2 face, using imported 6N/6P granular fill and uniaxial geogrids, was built up to 9.5 metres. At either end of the embankment, a 45° slope was constructed using the Tensartech NaturalGreen technology.
In a project which started in 2009, the A1’s existing dual two lane carriageways will be upgraded to dual three lane motorways. Access points for local traffic will be made safer, and agricultural traffic will be excluded.
