Mangoola Coal Stockpile Reclaim Tunnel, Muswellbrook, NSW Mangoola Coal Stockpile Reclaim Tunnel, Muswellbrook, NSW Mangoola Coal Stockpile Reclaim Tunnel, Muswellbrook, NSW Mangoola Coal Stockpile Reclaim Tunnel, Muswellbrook, NSW

Mangoola Coal Stockpile Reclaim Tunnel, Muswellbrook, NSW

Project featuring the Atlantic Civil Products MSE System

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General Information

Mangoola Coal is an open cut coal operation in the Wybong area, 20 kilometres west of Muswellbrook and approximately 10 kilometres north of the township of Denman, NSW. Mangoola Coal is based on a large, undeveloped coal reserve of approximately 150 million tonnes (Mt). Mangoola Coal aims to provide a long term, secure and profitable supply of high quality coal, whilst conducting operations in an environmentally responsible manner through the effective management, mitigation and offsetting of environmental impacts.

Downer Edi were engaged to project manage the concrete specialist “Holston Pty Ltd” and the earthworks contractor “Howlett Civil Pty Ltd”. The works involved the design and construction of : 5.8m wide, 650mm thick, 280linm long reinforced concrete slab to arch; a galvanised “Multi-plate Steel Arch” Product Reclaim tunnel; cast in-situ concrete beam surrounding both ends of arch profile; geotextile encapsulated /agg pipe gravel subsoil drainage @ base of arch footings & associated 5 coal valve inlet structures.

The subsequent bulk excavation in “rock” meant that the backfilling process either side of the arch (1:1 rock profile) had to be planned systematically to ensure backfilling operations were carried out strictly in accordance with specifications to control movements of arch without causing any eccentric loadings. Both ends of the arch required Atlantic Civil MSE walls to be erected whilst backfilling of arch was carried out concurrently.

Mangoola Coal Stockpile Reclaim Tunnel, Muswellbrook, NSW

 

Retaining Solutions scope involved the following installation of:

  • Unreinforced concrete levelling pad;
  • ACP MSE reinforced concrete facing panels; ACP galvanised soil reinforcing mats (lengths varying from 5m up to 7m), connecting pins, panel alignment pins, bearing pads and geotextile fabric to all vertical and horizontal panel joints;
  • Engineered Fall from height handrail system for both panel placement and wing walls;
  • MSE select backfill material (approx 3,869m3);
  • General backfill to rear of reinforced fill zone and 40% of length of arch (approx 18,000m3). Howlett Civil installed the general backfill zone in conjunction with Retaining Solutions wall erection operations, utilising dozers, scrapers and up to four 40tonne articulated dump trucks;
  • Vertical drainage in form of geotextile encapsulated gravel chimney drain to rear of reinforced fill zone (approx 410m2);
  • 50mm thick bedding sand layer; HDPE 2.5mm thick double textured membrane, including denso-tape sealant; geocomposite protection layer to seal entire MSE block at both ends of arch.

Retaining Solutions worked closely with Howlett Civil & XStrata to provide plant wet-hire (excavators and tracked bobcats) for the backfilling of both sides of the arch to ensure the target final completion date was achieved. Tracked bobcats were also used for conformance of subgrades surrounding the 5 coal valve inlet structures.


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Project Specs

  • Application - Reclaim Tunnel Headwalls
  • Product - Atlantic Civil Products MSE (ACP)
  • Finish - Plain Grey Smooth
  • Area - 410m2
  • Max. Height - 7.633m
  • Length - 90m
  • Loadings - 27m high Coal Stockpile & CAT D11R
  • Design life - 30 years
  • Owner - XStrata Coal
  • Client - Downer Edi
  • Construction - 5 weeks

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