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 3 span reinforced concrete structure was to be replaced on a similar footprint, but with a single 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. The retaining wall was driven along the central reservation on the approaches to the bridge. The wall was used to provide support to the bridge approach embankments, firstly retaining the north bound carriageway, then as works
proceeded the waling beams and anchors were switched to the opposite side to provide retention to
the south bound lanes as the build was completed.

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.

Completion date of the geotechnical work on site: 01/11/2017