MR92 Upgrade bulee to Nerriga, NSW MR92 Upgrade bulee to Nerriga, NSW MR92 Upgrade bulee to Nerriga, NSW MR92 Upgrade bulee to Nerriga, NSW MR92 Upgrade bulee to Nerriga, NSW

MR92 Upgrade Bulee to Nerriga, NSW

Project featuring the RECo TerraPlus® & RECo TerraMid® Systems

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General Information

The Bulee to Nerriga upgrade was located between Nowra and Nerriga and involved 54km of road upgrade between Hames Road near Nowra and Nerriga. The project was jointly funded by NSW Government and Shoalhaven City Council with a $22.5million funding and was to increase safety, travel time and reduce operating costs for commercial traffic. The project was divided into three stages to allow for smooth traffic flow throughout the course of the construction and each involved various works.

Nace Civil Engineering was awarded the contract in July 2007 for stage two with the scope of including development and implementation of management systems and plans, environmental management; traffic control; including ingress and egress of vehicles to worksite; clearing; earthworks; flexible pavement construction - 9km of realigning and sealing to the existing steep and narrow section from Bulee Gap to the Endrick River, a 60m long, four span concrete bridge near Bulee Gap, numerous gabion and reinforced earth retaining walls along the Bulee Gap and a large fauna underpass designed to allow koalas and other wildlife to cross the road safely just east of Endrick River.

Retaining Solutions scope of works involved the installation of the both precast panel and masonry segmental wall reinforced soil structures: TerraPlus® & TerraMid® Systems, mesh & strip soil reinforcement, filters and chimney drains and the placement, spreading and compaction of imported RSW backfill (26,000m3). Chimney drains were installed via the use of the Megaflo® drainage geocomposite system linked into to heel drains at the rear of the RSW zone. Both TerraPlus® & TerraMid® Systems are RMS R57 approved and can be designed for walls in excess of 9m high with 40kPa live loading. Numerous issues were resolved during the construction phase of these walls, including rough terrains causing difficulty to access the walls and affecting the productivity of construction. Constructions of these walls were completed over a duration of 12 months, starting in July 2008 through to June 2009.

MR92 Upgrade Bulee to Nerriga, NSW

About The Project

Retaining Solutions were also engaged to design, supply and install approx 10,500m3 of rock filled gabion mass gravity structures in a joint venture with Nviroscope Pty Ltd. Gabions and mattresses were used in applications such as gravity walls; batter protection, inlet and outlet scour protection; sedimentation basins, energy dissipators and spoon drains, The rock used within the gabions and mattresses was a “basalt rock” grading between 100mm to 250mm, sourced locally from Schmidt Quarries.

Key features of the mass gravity gabions walls were: the base of the walls were to be embedded in rock based upon the undulating/variability in terrain; “engineered fall-arrest system adopted throughout the construction - enabling safety of all personnel

at heights in excess of 2m”; walls were designed to retain steep batter arrangements (2:1) in addition to 25kPa live loading at pavement level.

Keighran Geotechnics were engaged for settlement assessment of retaining structures in addition to global stability (circular and non-circular failure modes) verification.

Nace were responsible for backfilling the general fill zone behind the gabion structures in locations where compaction equipment could be accessed. In locations where equipment was too large gabion rock was used to fill the wedge/void for widths less than 500mm behind the cages. Constructions of the gabion walls were completed over a duration of 18 months, starting in Feb 2008 through to July 2009.

Retaining Solutions experienced team and skilled operators were engaged on a wet-hire basis for batter protection and re-vegetation works through the entire upgrade for a further 6 months following completion of the retaining structures.

This project proving to be another example of Retaining Solutions Design Construct ability in providing a full turnkey solution.


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Project Specs

  • Application - Piled Bridge Abutments &Embankment Stabilisation
  • Product - RECo TerraPlus® System
    RECo TerraMid® System
    Rock Filled Gabions & Mattresses
  • Finish - Plain Grey, Masonry, Basalt Rock
  • Area - 1500m2 Panels
    2300m2 Masonry
    10 500m3 Gabions
  • Max. Height - 16.4m Panels
    9.4m Masonry
    9m Gabions
  • Length - 1400m
  • Loadings - 25kPa
  • Design life - 100 years
  • Owner - NSW Roads and Maritime Services
  • Client - Nace Civil Engineering Pty Ltd

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