The Magic of Combigrid®/Secugrid® Reinforcement for Piling Platforms

Emerging as one of Brisbane’s most stylish addresses is the $140 Million ‘Gallery House’project, located in Northshore Hamilton. The project was inspired by the natural textures, forms and shapes of the riverfront landscape. “Gallery House One” includes 169 apartments and approx. 1100m² retail in a 20 storey building with a single level basement, two storey podium and associated landscaping. “Gallery House Two” boasts 150 apartments and approx. 990m² retail in a 19 storey building with a single level basement, two storey podium and associated landscaping.

There were many challenges facing the development site prior to construction. With the construction site being located adjacent to the Brisbane River, it was ascertained that the existing sandy subgrade would prove to be problematic as it did not have the required bearing capacity. Thus, if left as it was it would not be able to withstand the proposed 370kPa piling rig pressures to be applied during operations and construction.

The contractors involved enlisted the services of a consultancy company to assist with this bearing capacity requirement/dilemma. Geoinventions Consulting Services (GCS) was engaged by Global Synthetics and Mainland Civil Pty Ltd to design a sufficiently thick working platform and provide design certification of the proposed Temporary Working Platforms (TWPs) to prevent any punching or bearing failures during the piling operations.

GCS designed an 800mm thick platform using a Combigrid® 40/40 at the subgrade interface and a Secugrid® 40/40 geogrid within the platform. Combigrid® is a composite product of a Secugrid® geogrid. The geogrid component provides the reinforcement, while the needle-punched nonwoven geotextile firmly welded between the reinforcement bars makes it well suited for soil stabilisation, separation and filtration tasks.

Combigrid® as a geocomposite geogrid has many advantages over a conventional biaxial grid, some of which include:

• Reinforcement, filtration, separation and drainage in just one product, reducing aggregate thickness

• Firmly bonded composite product

• Very high strength at low strains

• Immediate interlocking with cover aggregate

• High resistance against installation damage

Using Combigrid® and Secugrid® provided a considerable saving for the contractor by reducing the thickness of the platform compared to conventional working platform designs. This coupled with the ease of installation provided material savings, reduced labour costs and the project’s timeframe.

For further information contact amir@globalsynthetics.com.au