Client: Roads and Maritime Services (RMS)
Main Contractor: Georgiou Group
Project Value: $80 million
The New England Highway is proposed to be upgraded at Bolivia Hill, located 57.0km north of Glen Innes, NSW. The upgrade of the 2.1km section of road is to include realignment of the highway to improve poor horizontal alignment and steep grades. The existing two-lane highway will be upgraded by construction of a 325m long new bridge and excavation into the existing cutting to widen and realign the highway.
The Georgiou Group (GG) has been awarded the construction contract and GG in-turn has engaged Geoinventions to aid with the reinforced soil structure (RSS) retaining wall design. A very temporary high retaining wall was required to provide construction access to Pier 1 and Pier 2 for the new bridge during the two year construction period. Due to the existing sloping topography, the design needed to incorporate very steep slopes in front of the retaining walls.
The 9.0m high RSS retaining wall consisted of a wrap around mesh facing which was faced with geotextile as it’s a temporary wall with a design life of two years. The units were ordered to have a facing angle of 80 degrees which would be supported with tow steel brackets. This provided a rigid face during the compaction process. The wall was reinforced using a 100kN/m geogrid reinforcement at 600mm vertical spacings.
Besides having to support construction loading from Trucks and Vehicles, Georgiou requested that the wall be designed to accommodate a 135T Crawler Crane situated 5.0m away from the wall face. This equated to a surcharge load of 250kPa while construction materials were lifted to the Pier locations.
Geoinventions conducted both stress based and strain based design to ensure stability of the RSS retaining wall. Furthermore, Geoinventions engineers assisted the construction team with the installation training and continual site inspections to ensure construction quality was as per our design.
The construction of the retaining wall was completed within two months during August and September 2018. The entire project is expected to be completed late 2020.