Power Rd - Glendenning, NSW Power Rd - Glendenning, NSW Power Rd - Glendenning, NSW Power Rd - Glendenning, NSW

Power Rd - Glendenning, NSW

Project featuring the Keystone/Geogrid & Magnumstone Gravity System

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General Information

Coates Hire required a new depot & storage yard at Glendenning. The property is located on the southern side of Power Street at Glendenning. The site is trapezoidal in shape measuring approx 45m along Power Street frontage by about 100m deep. A vacant block of land abuts to the site on the west and M7 motorway forms part of the site boundary on the southern side. Based on the 1:100,000 geological map of Penrith, the site is underlain by Bringelly Shale of Wianamatta Group consisting of shale, carbonaceous claystone, laminite, fine to medium-grained lithic sandstone. Ground surface within the site slopes gently down to the south at angles of less than 3 degrees.

The proposed development required a reinforced soil wall to be constructed along the western boundary 4.4m high excavation (fill situation) and a gravity wall to be constructed within the northern carpark area 2.4m high (cut situation). A traditional reinforced concrete masonry wall was also required to separate the car park area and to retain the negative backslope to the M7 Motorway.

Christie Civil Pty ltd was awarded the contract with the scope of works involving overall site bulk cut/fill earthworks, subgrade preparation, DGS hardstands subgrades to future workshop/office pad, stormwater drainage, OSD detention tank and GPT installation, boundary fencing, kerb edging and final batter trimming/rock mattress installation, and associated retaining walls to cut and fill areas.

Retaining Solutions was engaged for the design, supply & installation of the Austral Keystone/geogrid System in the fill application and the Austral Magnumstone Gravity Wall System in the cut application.

Power Rd - Glendenning, NSW


The Austral Keystone System utilised “Acegrid GG120” (Tult 123kN/m) polyester geogrids. Due to the limited supply of crushed sandstone availability in the Sydney marketplace a recycled concrete DGB roadbase product was used as the imported RSW backfill. Due to the higher pH involved with this backfill higher factors of safety (FS=1.3) was adopted in terms of environment damage on the long-term performance of the geosynthetic. Specific design features of the RSW was to cater for 30kPa live load on the hardstand area in addition to a crash barrier and chain-link fence to be located between the front face of the wall and the concrete kerb edge to the hardstand (within the active zone). Alliance Geotechnical was engaged by Christie Civil to verify allowable foundation bearing capacities (170kPa) via DCP tests.

The Austral Magnumstone Gravity Wall System was used as an alternative to the previously specified concrete cribwall system. Apart from the appealing aesthetic appearance of Magnumstone product over traditional precast concrete cribwall systems, Magnumstone was chosen as it can be designed and built as a gravity wall up to heights of 4.8m, or in combination with geogrid soil reinforcement up to wall heights in excess of 10m. Again specific design features of this solution was that the Magnumstone wall face angle was 4.56deg compared to cribwall being 14degrees, i.e enabling pavement to be widened in vicinity of wall profile. The precast hollow core also enabled the wall facing to be filled near the top with quartzite rock ballast (70/150mm). The crash barrier was also located between the Magnumstone facing and the pavement kerb edge.

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Project Specs

  • Application - Cut & Fill Embankment Stabilisation
  • Product
    Keystone/Geogrid System
    Magnumstone Gravity System
  • Finish - Natural Grey
  • Face Area
    425m2 Keystone RSW
    228m2 Magnumstone
  • Max. Height
    4.4m Keystone RSW
    2.138m2 Magnumstone
  • Length
    143m Keystone RSW
    130m Magnumstone
  • Loadings - 30kPa
  • Design life - 100 years
  • Owner - Coates Hire
  • Client - Christie Civil Contracting Pty Ltd
  • Construction - 4 weeks

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