SHEET PILE RETENTION STRUCTURES ON A90 TRUNK ROAD, ABERDEEN WESTERN PERIPHERAL ROUTE/ BALMEDIE –TIPPERTY
MHB Consultants recently carried out a temporary works design associated with a replacement bridge carrying the A90 trunk road over the B979 Netherley Road, as part of the Aberdeen Western Peripheral Route/Balmedie-Tipperty (AWPR/B-T) project.
The existing reinforced concrete structure was to be replaced on a similar footprint, but with a wider span over the Netherley Road below to help form the new Stonehaven Junction. Another key project requirement was for the A90 to remain open to traffic in both directions throughout the works. To facilitate this, an anchored sheet pile retention structure was required to allow the existing bridge to be cut longitudinally, demolished sequentially and rebuilt in two halves. The retained height was up to 9.8m and the traffic loadings imposed resulted in a requirement to use heavy Larssen 605 steel sheet piles with three rows of waling beams with ground anchors.
Close liaison was required with the New Works Contractor, AWPR Construction Joint Venture, and our client, Albion Drilling, to ensure that the construction sequence was carefully thought through, and stability was maintained at each stage of the works.
The Phase 1 works (southbound closure) required 515kN working load ground anchors (type 75/53 by Ischebeck Titian) angled downwards at 45 degrees and terminated 4m into the sedimentary bedrock. For the Phase 2 works (northbound closure), the sheet pile wall was restrained by the use of an anchor wall embedded in compacted granular fill forming the new road embankment.
The sheet piling works were installed by LB Foundations with Albion Drilling carrying out the drilling and anchoring works. The temporary works were completed in October 2017.
The AWPR/B-T project is being delivered by Transport Scotland in partnership with Aberdeen City Council and Aberdeenshire Council. Aberdeen Roads Limited was awarded the contract to build the AWPR/B-T in December 2014 and has appointed the AWPR Construction Joint Venture, comprising Balfour Beatty, Carillion and Galliford Try, as the New Works Contractor to build the 58km road.
When complete, the AWPR/B-T will help reduce congestion, cut journey times, improve safety and lower pollution in Aberdeen City Centre. It will also enable local authorities to develop public transport solutions.
Photos at key stages of the construction are shown below (courtesy of AWPR Construction Joint Venture)