Sefton Triangle Access Bridge, Sefton NSW Sefton Triangle Access Bridge, Sefton NSW Sefton Triangle Access Bridge, Sefton NSW Sefton Triangle Access Bridge, Sefton NSW

Sefton Triangle Access Bridge, Sefton NSW

Project featuring the KeySteel® System.

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General Information

Arenco (NSW) Pty Ltd was contracted by ARTC to construct a bridge and associated approach ramps to provide access from Wellington Road to RailCorp Infrastructure. The proposed embankment to be constructed was from an existing elevated peninsula of land of 5m in height through to two converging rail cuttings. Due to the subsequent 30-degree skew of the proposed bridge a number of retaining wall options were considered ranging from in-situ concrete cantilevered walls through to Reinforced Earth™ panel and segmental block systems. The adopted solution was that of the KeySteel® System which enabled the walls to be constructed using skilled labour, tracked bobcat & compaction equipment (no requirements for excavator). The tight access and width of proposed embankment (6.5m wide) essentially dictated that the KeySteel® System was the easiest to construct in this application.

The two approach walls: MC01 - 40m long & MC02 – 43m long, involved the design & construction of a 6m high masonry concrete block reinforced soil walls using KeySteel®, Keystone Compac II, KeyStrip steel ladder soil reinforcements. The wall was required to support a uniform vertical live load surcharge equivalent to 20kPa and dead loads from the reinforced concrete integrated crash barrier/pavement spanning both walls. The top course of Keystone Compac blocks were stepped @ 200mm to grade to cater for the final ramp profile. The concrete parapet covered the top 400mm of wall profile.

Foundation assessment, chimney drainage design and global stability played an important role in this project to ensure all of these items were addressed prior to final design of the KeySteel® System. During bulk excavation of the railway cuttings, shale bedrock was visible in the cuttings. Very stiff to hard strength natural clays were overlying the shale bedrock.

Sefton Triangle Access Bridge, Sefton NSW


Subsequently all footings were to be founded on bedrock. Chimney drainage was designed utilising Stripdrain XS installed and the rear of the RSW block (2m cts) and connected through to outlets at the toe of the RSW zone. Global stability was verified by Jeffery & Katauskas Pty Ltd.

Another key feature of this project was that an external scaffold to the wall face could not be used for fall protection due to tight boundary constraints, the alternative utilised an innovative fall from height system using vertical/horizontal scaffold poles secured internally to prevent workers falling from height during both block placement and hand compaction operations.

Retaining Solutions scope of works involved the design and construction of the reinforced soil walls to NSW RTA QA Specification R57 “Design of Reinforced Soil Walls” & R58 “Construction of Reinforced Soil Walls”; installation of: KeySteel® Keystone Compac II blocks, fibreglass alignment pins, galvanised KeyStrip steel ladders and steel connecting pins, 20mm drainage aggregate, 100mm dia socked and slotted drainage aggregate pipe and placement, spreading & compaction of the imported select backfill (crusher dust) used within the reinforced fill zone. The works were carried out to a very tight construction programme on time, within budget and most importantly satisfying Arenco (NSW) Pty Ltd & ARTC strict OHS guidelines. Retaining Solutions produces with every wall complete, full quality documentation e.g Inspection & Test Plans, Daily Quality Verification Checklists in addition to detailed daily site diaries detailing operations and overall checks carried out over the duration of the wall construction from levelling pad placement to capping unit installation.

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Project Specs

  • Application - Abutment Approach Ramp
  • Product - KeySteel® System
  • Finish - Compac II Split Face 'Flushface'
  • Area - 350m2
  • Max. Height - 6.0m
  • Length - 83m
  • Loadings - 20kPa & Crash Barrier.
  • Design life - 100 years
  • Owner - ARTC
  • Client - Arenco (NSW) Pty Ltd
  • Construction - 3 weeks

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