Elizabeth St, Tighes Hill, Newcastle, NSW Elizabeth St, Tighes Hill, Newcastle, NSW Elizabeth St, Tighes Hill, Newcastle, NSW Elizabeth St, Tighes Hill, Newcastle, NSW

Elizabeth St, Tighes Hill, Newcastle, NSW

Project featuring the Concrib® System

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General Information

The Elizabeth St Tighes Hill road cutting was formed 100 years ago. The sandstone face is substantially stable but rock has fallen onto the road below and residents backyards have eroded such that their boundary is part-way down the cliff face. Elizabeth St has been closed to east bound traffic for two years.

The council went out to open tender to the marketplace in order to review a design and construct solution. Bolte Civil Pty Ltd were the successful tenderer which were engaged to design/supply and install a concrete cribwall solution in addition carrying out associated roadworks, stormwater, cliff face trimming and associated rock bolting if required. Retaining Solutions was engaged by Bolte Civil under subcontract to carry out the installation of the engineered cribwall system and associated backfilling operations.

The Concrib® system (1300 Macro’s headers) was used as the successful concrete cribwall product utilising galvanised steel reinforcement within all cribwall units in order to satisfy council stringent 100year design life specification.

Retaining Solutions crew operated within a very tight corridor which required careful management of materials handling and lifting techniques. Both zero swing excavators and Manitou (4:1 bucket/fork attachments) were used as effective methods for handling all materials. The reinforced concrete footing required approx 36 No steps being constructed due to the existing road grade profile running parallel with the cribwall.

Elizabeth St, Tighes Hill, Newcastle, NSW

 

Fall from height concerns were addressed utilising a concrete/block & static line system with all workers attached via harnesses due to heights exceeding 8m in some locations.

The Concrib® cribwall system was backfilled with 70 to 120mm size basalt aggregate backfill material. Where backfill width (distance between trimmed rock face and rear of cribwall headers) exceeded 1300mm, geogrid reinforcement was installed within the cribwall structure. Geotextile fabric “bidim A24” was installed/pinned against rock face and laid over gravel at underside of soil pug (3 headers from top of cribwall). Vertical PVC subsoil drains were also installed at the rear of cribwall which were connected to external inlet pits at the toe of the structure.

Retaining Solutions scope of works involved : Installation ONLY of Concrib® system components including; reinforced concrete footings; polyester geogrid reinforcement; non-woven geotextile over excavated embankment face; placement of cribwall infill 70 to 120mm basalt within crib silos and to rear of cribwall; soil plug within top 3 headers of wall in addition to surveyor conformance +/- 30mm.

The wall construction was completed on schedule subject to inclement weather delays, due to the close working relationship with the principal earthworks contractor Bolte Civil Pty Ltd.


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Project Specs

  • Application - Cut Embankment Stabilisation
  • Product - Concrib® System
  • Finish - Plain Grey
  • Area - 1010m2
  • Max. Height - 9m
  • Length - 164m
  • Loadings - 5kPa & 4:1 batter
  • Design life - 100 years
  • Owner - Newscastle City Council
  • Client - Bolte Civil Pty Ltd
  • Construction - 6 weeks

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