Reinforced Soil Walls and Slope Reinforcement
2017
Aberdeen, Scotland
Transport Scotland
AWPR JVC
AWPR JVC
AWPR A96
View of the Green Terramesh® slope
View of the Green Terramesh® slope
Heavy lifting crane supported by the Green Terramesh® slope
View of the completed works
24m span bridge with bank seats directly over the Green Terramesh®
Problem
The new ring road around Aberdeen Western Peripheral Route was part of the longest road project in 2015.
The project involved realigning the A96 to avoid a low headroom bridge which had been the cause of congestion and strikes. As the A96 is an extremely busy road, several options were considered to minimise disruption. The final decision was to install a temporary bridge over the road. The bridge allowed construction wagons to cross carriage traffic without disturbing road users.
A temporary works scheme design proposal was required for the support and stability of the embankment fill material using 6N fill material to stand at a 70-degree slope using reinforced earthworks. Reinforced embankment fill was then required between the support frames for the precast concrete beams and the integral bank seat to allow construction of the deck and parapet beams before removing the support frames.
Solution
The bridge, which was sub contracted to Balfour Beatty, began late in 2015 and stayed in place for 6 months until building works were complete. Working with Balfour Beatty, Maccaferri provided a solution using a combination of BBA Green Terramesh and Paralink slopes to support the temporary bridge. As a result, over 600m2 of Green Terramesh® was installed to form the 70-degree supporting slopes.
A horizontal load of 50kN/m imposed on the bank seat caused by traffic breaking on the bridge was also addressed separately. A traditional shear key setup would potentially cause deformation in the reinforced soil structure therefore Maccaferri proposed to utilise their high-strength Paralink 350 geogrid to act as a frictional anchorage by casting it into the bankseat and compacting an average of 1.5m of granular fill above. Paralink was also installed directly beneath the bank seat to reduce the potential of any deformation caused by the 100kPa vertical backseat load and 240kPa crane load. The temporary bridge had a 24m span and supported a vehicle carrying 80 tonnes of earth. Watch the bridge being erected in fast motion in this video created by AWPR